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A quartz microreactor containing 28 microchannels of 500 µm width and 105 mm length has been used to photoproduce hydrogen from liquid water-ethanol using an Au/TiO2 photocatalyst and UV light. The photomicroreactor has been tested in two flow configurations: (i) as a catalytic wall photoreactor by coating the microchannels with the photocatalyst, and (ii) as a slurry photoreactor by dispersing the photocatalyst in the liquid mixture of water-ethanol. The catalytic wall photoreactor configuration shows superior performance, with hydrogen yields more than three times higher than those obtained with the best slurry configuration under the same operation conditions.

This paper is focused on the photocatalytic hydrogen production on Pd/TiO2(-WO3) catalysts from water-methanol and water-glycerol mixtures under UVA and solar irradiation. The photodeposition method for Pd was studied varying conditions such as Pd amount, catalyst concentration and methanol concentration. The catalysts were tested at lab scale under simulated solar light and UVA radiation and also at large scale (25 L) under solar energy using a pilot-scale solar Compound Parabolic Collector (CPC). The catalysts characterization was performed by means of ICP-OES, N2 adsorption–desorption isotherms, XRD, HR-TEM, XPS and DR–UV–Vis spectroscopy. Hydrogen evolution was monitored by on-line gas chromatography.From results it was found the Pd photodeposition method plays a key role to increase the hydrogen evolution, affecting parameters like the Pd amount deposited, the Pd nanoparticles size and dispersion. The highest quantum efficiency (¿) obtained in this study was 11.8% and 41.2% under simulated solar and UVA irradiation, respectively, using Pd(0.24 wt%)/P25 in an aqueous solution of methanol (50 vol%). In the pilot-scale solar CPC, for Pd(0.24 wt%)//P25 catalysts in 5 vol% of methanol or glycerol as sacrificial agents, the quantum yield were 2.1 and 2.2%, respectively. When the concentration of the sacrificial agents decreased to 0.37 vol%, the quantum yields were 1.3 and 2.4% for methanol and glycerol, respectively. Compared to literature, the low noble metal content of these catalysts (0.25 wt%) seems to be a competitive factor considering their high price.

Bimetallic Pt–Pd catalysts supported on ceria have been prepared by mechanochemical synthesis and tested for lean methane oxidation in dry and wet atmosphere. Results show that the addition of platinum has a negative effect on transient light-off activity, but for Pd/Pt molar ratios between 1:1 and 8:1 an improvement during time-on-stream experiments in wet conditions is observed. The bimetallic samples undergo a complex restructuring during operation, starting from the alloying of Pt and Pd and resulting in the formation of unprecedented “mushroom-like” structures consisting of PdO bases with Pt heads as revealed by high-resolution transmission electron microscopy (HRTEM) analysis. On milled samples, these structures are well-defined and observed at the interface between palladium and ceria, whereas those on the impregnated catalyst appear less ordered and are located randomly on the surface of ceria and of large PdPt clusters. The milled catalyst prepared by first milling Pd metal and ceria followed by the addition of Pt shows better performances compared to a conventional impregnated sample and also to a sample obtained by inverting the Pd–Pt milling order. This has been ascribed to the intimate contact between Pd and CeO2 generated at the nanoscale during the milling process.

5-Hydroxymethylfurfural (HMF) is a biobased platform chemical that can be valorized into a spectrum of valuable products. In this report, supported Ir, Ir–Co, Ir–Ni, and Ir–Ru catalysts were investigated for this purpose. Only hydrogenation of HMF to 2,5-bis-(hydroxymethyl)furan (BHMF) occurred over all catalysts. The effect of the second metal (Co, Ni, and Ru) on Ir/SiO2 was reflected by the kinetic constants being in the order Ir–Ni/SiO2 > Ir–Co/SiO2 > Ir–Ru/SiO2. The oxophilic nature of the secondary metal improved the catalytic performance of the bimetallic catalysts compared to the monometallic iridium catalyst (Ir/SiO2). Addition of HCOOH and H2SO4 as cocatalysts is a strategy to reach one-pot conversion of HMF to 2,5-di-methylfuran (DMF). Over-hydrogenolysis products such as 2,5-dimethyltetrahydrofuran were formed when only H2SO4 was added, giving higher activity compared to addition of HCOOH. Simultaneous presence of acids gave the highest HMF conversion, promoting esterification to 5-formyloxymethyl furfural and allowing the one-pot transformation of HMF to DMF. Thermodynamic analysis of HMF transformations revealed that both hydrogenation and dehydration steps are feasible.

Gas-phase catalytic conversion of glycerol to value added chemicals was investigated over zinc-supported copper and nickel catalysts. The addition of aluminum in the support was also investigated in glycerol conversion and the results indicate an increase in the acidity and adsorption capacity for both copper and nickel catalysts. HRTEM and XRD analysis revealed NiZn alloy formation in the Ni/ZnO catalyst. The XRD patterns of the prepared ZnAl mixed oxide catalysts show the presence of Gahanite phase (ZnAl2O4). In addition, H2 chemisorption and TPR results suggest a strong metal-support interactions (SMSI) effect between Ni and ZnO particles. Bare supports ZnO and ZnAl (Zn/Al = 0.5) were investigated in the glycerol conversion and they did not present activity. Copper supported on ZnO and ZnAl mixed oxide (Zn/Al = 0.5) was active towards hydroxyacetone formation. Nickel was active in the hydrogenolysis of glycerol both for C–C and C–O bonds cleavage of glycerol producing CH4. Strong metal-support interactions (SMSI) between Ni and ZnO has a remarkable suppression effect on the methanation activity during the glycerol conversion.

3D-printed ceria structures have been prepared by robocasting, without using any additive, and impregnated with different amounts of Ni and Ru, characterized and tested for the catalytic decomposition of ammonia in a fixed bed reactor. The best catalytic performance has been achieved with an active phase of 0.5Ni0.1Ru (w/w %). A kinetic expression has been obtained using a crushed catalytic structure, which has been employed in a 1D model to simulate the behaviour of the Ni-Ru impregnated 3D-printed ceria structures. The results have been compared with the experimental data to validate the proposed model. A series of simulations have been performed to determine the relationship between the geometric parameters of the 3D-printed structures and their catalytic performance in the ammonia decomposition, in order to optimize the catalytic structure with the aim of supplying the hydrogen produced to a PEM-type fuel cell. Peer Reviewed Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant

Production of ‘renewable Methane’ has attracted renewed research interest as a fundamental probe reaction and process for CO2 utilization through potential use in C1 fuel production and even for future space exploration technologies. CO2 methanation is a structure sensitive reaction on Ni/CeO2 catalysts. To precisely elucidate the size effect of the Ni metal center on the CO2 methanation performance, we prepared 2%Ni/CeO2 catalysts with pre-synthesized uniform Ni particles (2, 4 and 8 nm) on a high surface area CeO2 support. Transmission electron microscopy (TEM) and ambient pressure X-ray photo spectroscopy (AP-XPS) characterization have confirmed that the catalyst structure and chemical state was uniform and stable under reaction conditions. The 8 nm sized catalyst showed superior methanation selectivity over the 4 and 2 nm counterparts, and the methanation activity in term of TOF is 10 times and 70 times higher than for the 4 and 2 nm counterparts, respectively. The DRIFTS studies revealed that the larger Ni (8 nm particles) over CeO2 efficiently facilitated the hydrogenation of the surface formate intermediates, which is proposed as the rate determining step accounting for the excellent CO2 methanation performance.

fff; International audience; Mo/TiO2 catalysts with atomic dispersion of molybdenum appear active and stable in the gas-phase hydrogenation of CO2. The comparison between various titania materials shows a crucial effect of the support surface structure on the methanol yield. Molybdenum supported at low coverage on rutile titania nanorods is the most active and methanol-selective system. From catalyst characterization by aberration-corrected scanning transmission electron microscopy, near-ambient pressure X-ray photoelectron spectroscopy, diffuse reflectance UV-vis spectroscopy, and temperature-programmed techniques, we suggest that the most active catalysts for methanol production involve atomically-dispersed oxomolybdate species with high reducibility and strong interaction with the rutile support.

Titanium dioxide mixed with reduced graphene oxide (rGO) has been tested in the photoproduction of hydrogen using UV light from water-ethanol combination in gas phase. The presence of the reduced graphene oxide in TiO2/rGO nanocomposites affects the physicochemical properties of hybrid materials, thus enhancing the photocatalytic activity. The obtained catalysts have been characterized for physical-chemical properties using X-ray diffraction (XRD), UV–vis spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM)/high-resolution transmission electron microscopy (HRTEM), and Brauner Emmett Teller (BET). The best photocatalyst has been obtained by mixing anatase and rGO (10 wt%) after calcination at 700 °C. This TiO2-rGO composite exhibited the highest performance with a hydrogen photogeneration rate of 9.5 mmol h-1 g-1.

Glucose oxidase (GOx) has been covalently immobilized onto plasma-treated low-density polyethylene (PT-LDPE) deposited by solvent-casting onto a glassy carbon electrode. PT-LDPE acts as a very simple and cheap mediator between the enzyme and the conducting substrate, the resulting electrode (GOx/PT-LDPE/GC) being able to detect effectively glucose under conditions of pH and temperature that mimic those of sweat. Glucose has been successfully monitored using GOx/PT-LDPE/GC electrodes via both, chronoamperometric and voltammetric measurements. The lowest limit of detection (LOD) was obtained with electrodes prepared with a GOx concentration of 5 mg/mL. This represents a significant reduction in the amount of enzyme as compared to electrodes obtained by dropping GOx onto PT-LDPE/GC (non-covalent immobilization), in which the required enzyme concentration was 33 mg/mL. Furthermore, the LOD has been decreased two orders of magnitude, from 1.3 mM for sensors without covalent immobilization to less than 0.05 mM. It is worth noting that the latter value is fully compatible with glucose concentration in sweat, which ranges from 0.06 to 0.11 mM for healthy patients and from 0.01 to 1 mM in diabetic patients. Moreover, the developed sensor is able to promote the reduction of hydrogen peroxide produced during the oxidation of glucose to gluconolactone.

Ligands are a fundamental part of nanocrystals. They control and direct nanocrystal syntheses, and provide colloidal stability. Bound ligands also affect the nanocrystals’ chemical reactivity and electronic structure. Surface chemistry is thus crucial to understand nanocrystal properties and functionality. Here, we investigate the synthesis of metal oxide nanocrystals (CeO2-x, ZnO, and NiO) from metal nitrate precursors, in the presence of oleylamine ligands. Surprisingly, the nanocrystals are capped exclusively with a fatty acid instead of oleylamine. Analysis of the reaction mixtures with nuclear magnetic resonance spectroscopy revealed several reaction byproducts and intermediates that are common to the decomposition of Ce, Zn, Ni and Zr nitrate precursors. Our evidence supports the oxidation of alkylamine and formation of a carboxylic acid, thus unraveling this counterintuitive surface chemistry.

Graphene oxide (GO) has been synthesized by a modification of the Hummers’ method using different times of reaction of 30, 60, 120, 300 and 540 min while maintaining all other parameters constant and avoiding aggressive posttreatments such as sonication and strong agitation that are known to affect the chemical and structural integrity of the flakes. The morphology of the obtained flakes has been investigated by optical and electron microscopies. Chemical properties of the GOs have been determined by TGA, XRD, Raman, XPS and EDS. The degree of exfoliation strongly increased with the reaction time, while no significant differences were found between the GOs in terms of their chemistry. Thus, we demonstrate that increasing reaction time is enough for the obtention of large-sized and well-exfoliated GO flakes, while maintaining a chemical richness that would be hindered by aggressive exfoliation techniques.

The cost-effective conversion of low-grade heat into electricity using thermoelectric devices requires developing alternative materials and material processing technologies able to reduce the currently high device manufacturing costs. In this direction, thermoelectric materials that do not rely on rare or toxic elements such as tellurium or lead need to be produced using high-throughput technologies not involving high temperatures and long processes. BiSe is an obvious possible Tefree alternative to BiTe for ambient temperature thermoelectric applications, but its performance is still low for practical applications, and additional efforts toward finding proper dopants are required. Here, we report a scalable method to produce BiSe nanosheets at low synthesis temperatures. We studied the influence of different dopants on the thermoelectric properties of this material. Among the elements tested, we demonstrated that Sn doping resulted in the best performance. Sn incorporation resulted in a significant improvement to the BiSe Seebeck coefficient and a reduction in the thermal conductivity in the direction of the hot-press axis, resulting in an overall 60% improvement in the thermoelectric figure of merit of BiSe ., M.L., Y.Z., T.Z. and K.X. thank the China Scholarship Council for their scholarship support. Y.L. acknowledges funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 754411. J.L. thanks the ICREA Academia program and projects MICINN/FEDER RTI2018-093996-B-C31 and G.C. 2017 SGR 128. ICN2 acknowledges funding from the Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO ENE2017-85087-C3.

Ceria-supported Ni-Ru bimetallic catalysts with different metal loadings have been prepared by co-impregnation, characterized and tested in the production of hydrogen from the catalytic decomposition of ammonia. The bimetallic catalysts showed an excellent catalytic performance in long-term stability tests with respect to monometallic Ru/CeO2 and Ni/CeO2 and in multicycle tests under pure ammonia. The best catalytic performance has been obtained over catalysts with 2.4-5 wt.% Ni, 0.4-0.6 wt.% Ru, and a Ni/Ru wt.% ratio of ca. 7. TOFH2 values exceeding 2 s-1 have been obtained, which are among the highest reported for ammonia decomposition at 400 °C. Raman spectroscopy, XRD, HRTEM, XPS, TPR and H2 chemisorption have revealed the existence of an intimate contact between Ni and Ru and CeO2, which is considered the reason of the excellent catalytic activity and stability observed. A kinetic model has been developed using the Langmuir-Hinshelwood-Hougen-Watson approach for the decomposition of ammonia in a fixed bed reactor. The reaction rate expression of the ammonia decomposition on Ni-Ru bimetallics supported on ceria suggests that the dehydrogenation of the ammonia adsorbed on the surface of the catalyst is the limiting step of the reaction and that ammonia decomposition is inhibited by the presence of H2.

Ceria nanoshapes exhibiting different amounts of {100}, {110} and {111} facets (cubes, rods, octahedra and polyhedra) were prepared, characterized, tested in the carbon soot oxidation reaction, and studied by operando near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and operando Raman spectroscopy up to 550 °C. The specific soot oxidation reaction rate (mgC·m-2·min-1) clearly indicated that the {110} and {100} crystallographic planes of ceria were more active than the {111} ones for the oxidation of carbon soot. As deduced from the Ce 3d and O 1s signals recorded using different photon energies, all ceria nanoshapes experienced progressive reduction upon increasing the temperature under Ar, which was accompanied by the formation of oxygen vacancies. Raman studies revealed that, at this stage, isolated graphene layers in carbon soot reacted with ceria lattice oxygen atoms following a Mars-Van Krevelen mechanism. After exposure to O2 at 550 °C, a broad signal in the O 1s region at 531.2–532.5 eV was ascribed to surface active oxygen species, such as peroxide (O22-) and superoxide (O2-) species, generated from the interaction of molecular O2 with oxygen vacancies, which proved to be highly reactive to oxidize the graphitic structures of carbon soot.

We successfully 3D printed Au/TiO2 monoliths for photogenerating hydrogen from water/ethanol gaseous mixtures under dynamic conditions. Monolith designs were printed by additive superposition of microfilaments of titania-based pastes. Factors influencing the efficiency of the photocatalytic reactions, including impregnation of gold nanoparticles (Au NPs), calcination temperature, diameter of microfilaments and monolith design, are investigated. The use of preformed Au NPs assured a constant Au particle size (ca. 4 nm) for all samples, which allowed to a precise assessment of the effect of the design of 3D-printed titania monoliths on photocatalytic activity. The impregnation of preformed Au NPs before or after the 3D printing process has a strong influence on the photocatalytic efficiency. The pre-impregnated monoliths have a homogeneous Au NPs distribution throughout the microfilaments, whereas the post-impregnated ones present an asymmetric distribution of Au NPs, observing a high gold concentration at the surface and lower gold concentrations in the inner regions of the printed microfilaments. The gold concentration of the Au-loading suspension was reduced ca. 10 times in post-impregnated samples to ensure a similar amount of Au NPs anchored at the surface of the microfilaments, according to an XPS analysis of the pre- and post-impregnated samples. Although the photocatalytic performance of the pre-impregnated monoliths was improved when samples were calcined at 400 °C, due to a stronger contact between the Au NPs and the microfilament supports, the post-impregnated samples with 100 times lower Au concentration (0.005 wt.%) exhibited enhanced catalytic performances. Under similar geometric open section and photon absorption conditions, the photoproduction of hydrogen on a weight (or volume) basis increased strongly as the diameter of the filaments decreased, which is explained by a progressive increase of the surface-to-weight and surface-to-volume ratios. The best photoactivity was obtained with a post-impregnated titania monolith 3D printed with microfilaments with 200 μm in diameter, which yielded 0.24 mol H2 min−1 gAu−1.

Ceria-supported Ni, Ru and Ni Ru catalysts have been tested in the catalytic decomposition of ammonia to yield hydrogen and their performance in long-term tests has been compared to alumina-supported Ni and Ru samples. The catalysts have been characterized by XRD, TPR, NH3-TPD, HAADF-STEM, SEM, BET and XPS. Ceria-based samples are more active in ammonia decomposition with respect to their alumina-based counterparts, which has been ascribed to a particular metal-support interaction, while acidity does not seem to play an important role. Ru-based catalysts are more active than Ni-based samples, but they deactivate rapidly, in particular the Ru/Al2O3 sample. This is ascribed to loss of exposed Ru, as demonstrated by XPS and HAADF-STEM. Considering the high cost and limited availability of Ru, the Ni/CeO2 catalyst appears as a promising system for ammonia decomposition due to its good performance and low cost. In situ XPS experiments reveal that the active sites for the catalytic decomposition of ammonia are metallic Ni and Ru. Bimetallic Ni Ru catalysts do not outperform their monometallic counterparts, irrespective of the order in which the metals are added.

One of the main issues for the catalytic abatement of methane from natural gas fueled vehicles over Pd-based materials is due to the large amount of water vapor in the exhausts, which can severely deactivate the catalyst. In this work, we investigated the effect of water added during methane oxidation on a series of silica doped Pd/ceria catalysts prepared by solution combustion synthesis, using different characterization techniques. The results obtained by coupling Temperature Programmed Oxidation (TPO) experiments and High Resolution Transmission Electron Microscopy (HRTEM) indicate that the mechanism of PdO-Pd-PdO phase transformation over Si-doped catalysts is different in dry and wet conditions. The presence of water not only shifts the onset of PdO decomposition to higher temperature, but also PdO-Pd transition is found to proceed via the formation of multi-domain PdO/Pd particles. This effect is tentatively attributed to the suppression of oxygen exchange induced by the presence of stable hydroxyl groups on silica.

Co-doped titanium dioxide was synthesized by doping with manganese (Mn) and cerium (Ce) through a sol-gel method for the degradation of diclofenac (DCF). The synthesized products were successfully characterized by X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Nitrogen physisorption at 77 K, X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance (UV-DRS), photoluminescence spectroscopy (PL) and total organic carbon (TOC). It was shown that co-doping increased the specific surface area, improved the visible light absorption and extended the lifetime of photogenerated charge carriers. Furthermore, the results of the photocatalytic experiments show that the photodegradation rate of diclofenac can be approached by pseudo first-order kinetics and it followed the Langmuir-Hinshelwood model very well. The co-doped catalyst with 0.6% Mn and 1% Ce molar ratios appeared to be the most photoactive catalyst with 94% of DCF removal and an apparent rate constant of 0.012 min−1.

Because of the problems associated with the generation and storage of hydrogen in portable applications, the use of ammonia has been proposed for on-site production of hydrogen through ammonia decomposition. First, an analysis of the existing systems for ammonia decomposition and the challenges for this technology are presented. Then, the state of the art of the catalysts used to date for ammonia decomposition is described considering the catalysts composed of noble and non-noble metals and their combinations, as well as novel materials such as alkali metal amides and imides. The effect of the supports and promoters used is analyzed in detail, and the catalytic activity obtained is compared. An analysis of the kinetics of the reaction obtained with different catalysts is also presented and discussed, including the reaction mechanism, the determining step of the reaction, and the apparent activation energy. Finally, the structured reactors used to date for the decomposition reaction of ammonia are explored, as well as the possibilities offered by catalytic membrane reactors, which allow the on-site simultaneous production and separation of hydrogen.

Hydrogen, produced by water splitting, has been proposed as one of the main green energy vectors of the future if produced from renewable energy sources. However, to substitute fossil fuels, large amounts of pure water are necessary, scarce in many world regions. In this work, we fabricate efficient and earth-abundant electrodes, study the challenges of using real seawater, and propose an electrode regeneration method to face undesired salt deposition. Ni−Mo−Fe trimetallic electrocatalyst is deposited on non-expensive graphitic carbon felts both for hydrogen (HER) and oxygen evolution reactions (OER) in seawater and alkaline seawater. Cl pitting and the chlorine oxidation reaction are suppressed on these substrates and alkalinized electrolyte. Precipitations on the electrodes, mainly CaCO, originating from seawater-dissolved components have been studied, and a simple regeneration technique is proposed to rapidly dissolve undesired deposited CaCO in acidified seawater. Under alkaline conditions, Ni−Mo−Fe-based catalyst is found to reconfigure, under cathodic bias, into Ni−Mo−Fe alloy with a cubic crystalline structure and Ni : Fe(OH) redeposits whereas, under anodic bias, it is transformed into a follicular Ni:FeOOH structure. High productivities over 300 mA cm and voltages down to 1.59 V@10 mA cm for the overall water splitting reaction have been shown, and electrodes are found stable for over 24 h without decay in alkaline seawater conditions and with energy efficiency higher than 61.5 % which makes seawater splitting promising and economically feasible., Authors from IREC acknowledge Generalitat de Catalunya for financial support through the CERCA Programme. J.R.M. acknowledges Generalitat de Catalunya for financial support through the CERCA Programme, M2E (2017 SGR 1246). IREC and ICN2 also acknowledge additional support by the European Regional Development Funds (ERDF, FEDER) and by MINECO coordinated project ENE2017-85087-C3. ICN2 was supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. ICN2 acknowledges funding from Generalitat de Catalunya SEV-2017-0706). J.L. and X.G. are grateful to projects MICINN/FEDER RTI2018-093996-B−C31 and Generalitat de Catalunya 2017 SGR 128. X.G. is grateful to Generalitat de Catalunya for PhD grant 2017 FI_B 00137. JL is a Serra Húnter fellow and is grateful to ICREA Academia program.

Photocatalytic H2 evolution from ethanol dehydrogenation is a convenient strategy to store solar energy in a highly valuable fuel with potential zero net CO2 balance. Herein, we report on the synthesis of CoTiO3/TiO2 composite catalysts with controlled amounts of highly distributed CoTiO3 nanodomains for photocatalytic ethanol dehydrogenation. We demonstrate these materials to provide outstanding hydrogen evolution rates under UV and visible illumination. The origin of this enhanced activity is extensively analyzed. In contrast to previous assumptions, UV–vis absorption spectra and ultraviolet photoelectron spectroscopy (UPS) prove CoTiO3/TiO2 heterostructures to have a type II band alignment, with the conduction band minimum of CoTiO3 below the H2/H+ energy level. Additional steady-state photoluminescence (PL) spectra, time-resolved PL spectra (TRPLS), and electrochemical characterization prove such heterostructures to result in enlarged lifetimes of the photogenerated charge carriers. These experimental evidence point toward a direct Z-scheme as the mechanism enabling the high photocatalytic activity of CoTiO3/TiO2 composites toward ethanol dehydrogenation. In addition, we probe small changes of temperature to strongly modify the photocatalytic activity of the materials tested, which could be used to further promote performance in a solar thermophotocatalytic reactor., This work was supported by projects MICINN/FEDER RTI2018-093996-B-C31 and RTI2018-095498-J-I00. J.A., T.Z., and X.H. thank funding from GC 2017 SGR 327 and the MINECO project (ENE2017-85087-C3). ICN2 thanks the support from the Severo Ochoa program (MINECO, no. SEV-2013-0295) and the CERCA program/Generalitat de Catalunya. N.G. and Y.L. thank the Swiss National Science Foundation (SNF) for funding under the Ambizione Energy (no. PZENP2_166871). Y.Z., C.X., X.W., and T.Z. acknowledge the China Scholarship Council (CSC) for scholarship support. Part of the present work has been performed in the framework of the Universitat Autónoma de Barcelona Materials Science PhD program. J.L. is a Serra Hunter fellow and is grateful to GC 2017 SGR 128 and the ICREA Academia program.

This work reports the design, manufacturing and catalytic activity characterization of a micro-reformer for hydrogen-rich gas generation integrated in portable-solid oxide fuel cells (μ-SOFCs). The reformer has been designed as a silicon micro monolithic substrate compatible with the mainstream microelectronics fabrication technologies ensuring a cost-effective high reproducibility and reliability. Design and geometry of the system have been optimized comparing with the previous design, consisting in an array of more than 7x103 vertical through-silicon micro channels perfectly aligned (50 μm diameter) and a 5 W integrated serpentine heater consisting of three stacked metallic layers (TiW, W and Au) for perfect adhesion and passivation. Traditional fuels for SOFCs, such as ethanol or methanol, have been replaced by dimethyl ether (DME) and the chosen catalyst for DME conversion consists of Pd nanoparticles grafted on an alumina active support. The micro-channels have been coated by atomic layer deposition (ALD) with amorphous Al2O3 and the influence of rapid thermal processing (RTP) on such film has been studied. A customized ceramic 3D-printed holder has been designed to measure the specific hydrogen production rates, DME conversion and selectivity profiles of such catalyst at different temperatures.

SBA-15 mesoporous silica materials with zirconium atoms incorporated into its structure were prepared by two methods: direct-synthesis and pH-adjustment. Two nominal ratios of Zr/Si = 0 and 0.10 were evaluated. N2-physisorption, X-ray powder diffraction (XRPD) and, X-ray Photoelectron Spectroscopy (XPS) revealed that the morphology and structural order of the SBA-15 materials were greatly affected by the partial incorporation of zirconium into the SBA-15 structure as well as by the synthesis method. High-resolution transmission electron microscopy (HRTEM) of the materials prepared by pH-adjustment (SBA-15-2 and Zr-SBA-15-2 samples) revealed a more perfectly defined mesoporous structure with long-range ordering when compared with the materials obtained by direct-synthesis (SBA-15-1 and Zr-SBA-15-1 samples). The results by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Energy-Dispersion X-ray Spectroscopy (EDX) to evaluate the elemental composition of the materials indicated a better correlation using the pH-adjustment method.

A cost-effective and scalable approach was developed to produce monodisperse Ni2−xCoxP nanocrystals (NCs) with composition tuned over the entire range (0 ≤ x ≤ 2). Ni2−xCoxP NCs were synthesized using low-cost, stable and low-toxicity triphenyl phosphite (TPP) as a phosphorus source, metal chlorides as metal precursors and hexadecylamine (HDA) as a ligand. The synthesis involved the nucleation of amorphous Ni–P and its posterior crystallization and simultaneous incorporation of Co. The composition, size and morphology of the Ni2−xCoxP NCs could be controlled simply by varying the ratio of Ni and Co precursors and the amounts of TPP and HDA. Ternary Ni2−xCoxP-based electrocatalysts exhibited enhanced electrocatalytic activity toward the hydrogen evolution reaction (HER) compared to binary phosphides. In particular, NiCoP electrocatalysts displayed the lowest overpotential of 97 mV at J = 10 mA cm−2 and an excellent long-term stability. DFT calculations of the Gibbs free energy for hydrogen adsorption at the surface of Ni2−xCoxP NCs showed NiCoP to have the most appropriate composition to optimize this parameter within the whole Ni2−xCoxP series. However, the hydrogen adsorption energy was demonstrated not to be the only parameter controlling the HER activity in Ni2−xCoxP., J. David and J. Arbiol acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project VALPEC (ENE2017-85087-C3). ICN2 acknowledges support from the Severo Ochoa Programme (SEV-2013-0295) and is funded by the CERCA Programme/Generalitat de Catalunya. J. David has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 665919. J. Llorca is a Serra Hunter Fellow and is grateful to the ICREA Academia program and grants MINECO/FEDER ENE2015-63969-R and GC 2017 SGR 128. J. Liu, J. Li and X. Yu thank the China Scholarship Council for scholarship support. M. Meyns acknowledges a Juan de la Cierva formación grant by the Spanish MINECO.

The shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPS) hamper the practical application of lithium–sulfur batteries (LSBs). Toward overcoming these limitations, herein an in situ grown CN@NbSe heterostructure is presented with remarkable specific surface area, as a Li–S catalyst and LiPS absorber. Density functional theory (DFT) calculations and experimental results comprehensively demonstrate that CN@NbSe is characterized by a suitable electronic structure and charge rearrangement that strongly accelerates the LiPS electrocatalytic conversion. In addition, heterostructured CN@NbSe strongly interacts with LiPS species, confining them at the cathode. As a result, LSBs cathodes based on CN@NbSe/S exhibit a high initial capacity of 1545 mAh g at 0.1 C. Even more excitingly, CN@NbSe/S cathodes are characterized by impressive cycling stability with only 0.012% capacity decay per cycle after 2000 cycles at 3 C. Even at a sulfur loading of 5.6 mg cm, a high areal capacity of 5.65 mAh cm is delivered. These results demonstrate that CN@NbSe heterostructures can act as multifunctional polysulfide mediators to chemically adsorb LiPS, accelerate Li-ion diffusion, chemically catalyze LiPS conversion, and lower the energy barrier for LiS precipitation/decomposition, realizing the “adsorption-diffusion-conversion” of polysulfides., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economíay Competitividad through the project SEHTOP, ENE2016- 77798-C4-3-R, and ENE2017-85087-C3. D.Y., C.Z. and M.L. thank the China Scholarship Council for the scholarship support (CSC 201806090276, CSC 201706650011 and CSC 201706890005, respectively). Z.L. acknowledges funding from MINECO SO FPI Ph.D. grant (SEV-2013-0295-17-1). The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128, and to ICREA Academia program. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. M.C.S. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No 754510 (PROBIST). M.B. acknowledges support from SUR Generalitat de Catalunya and the EU Social Fund; project ref. 2020 FI 00103.

The increasing diffusion of alternative mobility solutions, ranging from electric technologies to natural gas fueled vehicles (NGVs), has led to a progressive life-cycle analysis approach of their environmental impact in terms of greenhouse gases (GHGs) emissions. This new approach prompted a careful design of the NGVs catalytic aftertreatment system in order to minimize the catalytic converter carbon footprint as well as the unburned methane emissions at tailpipe. Here, a series of Pd/CeO2 methane oxidation catalysts were prepared by an environmentally friendly solvent-free method and compared to the commercial wet-synthesized state-of-the-art catalysts. Their application in NGVs aftertreatment systems was evaluated by testing powder catalysts and coated monolith cores for CH4 oxidation and steam reforming, which are the main methane abatement reactions occurring in a three-way catalyst (TWC) under lean and rich conditions, respectively. Pd/CeO2 catalysts prepared by mechanochemical synthesis initially displayed superior activity compared to their counterpart obtained by conventional wet impregnation, especially under lean oxidation conditions, but appeared less resistant to the industrial aging process after core washcoating. Lambda sweep experiments carried out under full gas composition proved that, despite needing further optimization in the washcoating and aging processes, the developed mild milling synthesis procedure is a viable way for the production of Pd/CeO2 based catalysts for natural gas TWCs.

Shiva Fazlikeshteli ha guanyat el Premi a la millor presentació oral per aquest article a la 12th International Conference on Hydrogen Production (ICH2P-2021). The catalytic production of syngas by the partial oxidation of methane (POM) was investigated over Pd supported on ceria (0.5–2 Pd wt.%) prepared by incipient wetness impregnation and by mechanochemical methods. The performance of the Pd/CeO2 catalyst prepared by milling CeO2 and Pd acetate was superior to that prepared by milling CeO2 and Pd nitrate and to Pd/CeO2 prepared by impregnation from Pd acetate. The best catalytic activity of the Pd/CeO2 catalyst prepared from CeO2 and Pd acetate was obtained by milling at 50 Hz for 5 min. Two-step combustion and reforming reaction mechanism were identified. Remarkably, methane conversion increased progressively with Pd loading for the catalysts prepared by incipient wetness impregnation, whereas low metal loading showed better conversion of methane for the catalysts prepared by ball milling using Pd acetate. This was explained in terms of an impressive dispersion of Pd species with a strong interaction with the surface of ceria, as deduced from transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy characterization, which revealed a large quantity of highly oxidized species at the surface. Peer Reviewed Award-winning

Atomically dispersed metals maximize the number of catalytic sites and enhance their activity. However, their challenging synthesis and characterization strongly complicates their optimization. Here, the aim is to demonstrate that tuning the electronic environment of atomically dispersed metal catalysts through the modification of their edge coordination is an effective strategy to maximize their performance. This article focuses on optimizing nickel-based electrocatalysts toward alcohol electrooxidation in alkaline solution. A new organic framework with atomically dispersed nickel is first developed. The coordination environment of nickel within this framework is modified through the addition of carbonyl (CO) groups. The authors then demonstrate that such nickel-based organic frameworks, combined with carbon nanotubes, exhibit outstanding catalytic activity and durability toward the oxidation of methanol (CHOH), ethanol (CHCHOH), and benzyl alcohol (CHCHOH); the smaller molecule exhibits higher catalytic performance. These outstanding electrocatalytic activities for alcohol electrooxidation are attributed to the presence of the carbonyl group in the ligand chemical environment, which enhances the adsorption for alcohol, as revealed by density functional theory calculations. The work not only introduces a new atomically dispersed Ni-based catalyst, but also demonstrates a new strategy for designing and engineering high-performance catalysts through the tuning of their chemical environment., ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme /Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. Z.L. acknowledges funding from MINECO SO-FPT Ph.D. grant (SEV-2013-0295-17-1). This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 823717-ESTEEM3. The present work is supported by the European Regional Development Fund and by the Spanish MINECO through the projects ENE2016-77798-C4-3-R, ENE2017-85087-C3, and project NANOGEN (PID2020-116093RB-C43). X.W. and T.Z. thank the China Scholarship Council for the scholarship support. P. Tang acknowledges the Humboldt Research Fellowship. Authors acknowledge funding from Generalitat de Catalunya 2017SGR327 and 2017SGR1246. L.L. acknowledges the support from Natural Sciences and Engineering Research Council of Canada (NSERC, DG RGPIN-2020-06675). J.L. is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128, and to ICREA Academia program.

Cu2-xS has become one of the most promising thermoelectric materials for application in the middle-high temperature range. Its advantages include the abundance, low cost, and safety of its elements and a high performance at relatively elevated temperatures. However, stability issues limit its operation current and temperature, thus calling for the optimization of the material performance in the middle temperature range. Here, we present a synthetic protocol for large scale production of covellite CuS nanoparticles at ambient temperature and atmosphere, and using water as a solvent. The crystal phase and stoichiometry of the particles are afterward tuned through an annealing process at a moderate temperature under inert or reducing atmosphere. While annealing under argon results in Cu1.8S nanopowder with a rhombohedral crystal phase, annealing in an atmosphere containing hydrogen leads to tetragonal Cu1.96S. High temperature X-ray diffraction analysis shows the material annealed in argon to transform to the cubic phase at ca. 400 K, while the material annealed in the presence of hydrogen undergoes two phase transitions, first to hexagonal and then to the cubic structure. The annealing atmosphere, temperature, and time allow adjustment of the density of copper vacancies and thus tuning of the charge carrier concentration and material transport properties. In this direction, the material annealed under Ar is characterized by higher electrical conductivities but lower Seebeck coefficients than the material annealed in the presence of hydrogen. By optimizing the charge carrier concentration through the annealing time, Cu2-xS with record figures of merit in the middle temperature range, up to 1.41 at 710 K, is obtained. We finally demonstrate that this strategy, based on a low-cost and scalable solution synthesis process, is also suitable for the production of high performance Cu2-xS layers using high throughput and cost-effective printing technologies., This work was supported by the European Regional Development Funds. M.Y.L., X.H., T.Z., and K.X. thank the China Scholarship Council for scholarship support. M.I. acknowledges financial support from IST Austria. J.L. acknowledges support from the National Natural Science Foundation of China (No. 22008091), the funding for scientific research startup of Jiangsu University (No. 19JDG044), and Jiangsu Provincial Program for High-Level Innovative and Entrepreneurial Talents Introduction. J.L. is a Serra Húnter fellow and is grateful to the ICREA Academia program and projects MICINN/FEDER RTI2018-093996-B-C31 and GC 2017 SGR 128. ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO ENE2017-85087-C3. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. T.Z. has received funding from the CSC-UAB PhD scholarship program.

Thiolate protected metal clusters are valuable precursors for the design of tailored nanosized catalysts. Their performance can be tuned precisely at atomic level, e.g. by the configuration/ type of ligands or by partial/complete removal of the ligand shell through controlled pre-treatment steps. However, the interaction between the ligand shell and the oxide support, as well as ligand removal by oxidative pre-treatment, are still poorly understood. Typically, it was assumed that the thiolate ligands are simply converted into SO 2 , CO 2 and H 2 O. Herein, we report the first detailed observation of sulfur ligand migration from Au to the oxide support upon deposition and oxidative pre-treatment, employing mainly S K-edge XANES. Conse- quently, thiolate ligand migration not only produces clean Au cluster surfaces but also the surrounding oxide support is modified by sulfur-containing species, with pronounced effects on catalytic properties

A series of Ni supported over MgAl2O4–CeO2 catalysts have been prepared by the wet impregnation method as catalysts for steam ethanol reforming. The synthesis was performed using nitrilotriacetic acid (NTA) or citric acid (CA) as chelating agents (L) with different L/Ni molar ratios. The features of catalytic solids were determined by DR–UV–Vis–NIR, FTIR, BET, TGA, XRD, H2–TPR, XPS, Raman, HRTEM and SEM. Changes in the crystallite size of NiO and CeO2 were evidenced with the use of NTA, while the addition of CA allowed to reduce the crystallite size of NiO and Ni with a slight effect in CeO2 size. The use of chelating agents induced changes in the Ni-CeO2 interactions and an increase in the Ce/Ni0 surface ratio. Catalytic systems prepared using an L/Ni ratio leading to the most stable complex formation (NTA/Ni=1 and CA/Ni=2) exhibited the best performances in the reforming reaction under the operation conditions studied.

Reducing the metal particle size on semiconductor-based materials from a few nanometers down to well-dispersed clusters or single atoms has been demonstrated to be an effective strategy to enhance the photocatalytic performance. However, designing a simple and fast synthesis procedure has consistently been a challenge. In this work, gold clusters have been easily synthesized and dispersed onto TiO2 surface by one-step ball milling from TiO2 and gold acetate. The Au clusters strongly interact with TiO2 and the resulting material exhibits outstanding photocatalytic performances on the generation of hydrogen under UV and visible light, which double those obtained on conventional Au/TiO2 photocatalysts containing Au nanoparticles. We have studied the effect of various preparation parameters and characterized the samples by a variety of microscopic and spectroscopic techniques. The particular architecture accomplished by ball milling results in efficient charge separation, low charge transfer resistance and high photocurrent response. This mechanochemical method not only provides a facile and cost-effective alternative to the conventional methods of fabricating Au/TiO2 catalysts, but also opens a promising avenue for developing other ultrasmall metal clusters onto different supports.

Direct ethanol fuel cells (DEFCs) show a huge potential to power future electric vehicles and portable electronics, but their deployment is currently limited by the unavailability of proper electrocatalysis for the ethanol oxidation reaction (EOR). In this work, we engineer a new electrocatalyst by incorporating phosphorous into a palladium-tin alloy and demonstrate a significant performance improvement toward EOR. We first detail a synthetic method to produce Pd2Sn:P nanocrystals that incorporate 35% of phosphorus. These nanoparticles are supported on carbon black and tested for EOR. Pd2Sn:P/C catalysts exhibit mass current densities up to 5.03 A mgPd−1, well above those of Pd2Sn/C, PdP2/C and Pd/C reference catalysts. Furthermore, a twofold lower Tafel slope and a much longer durability are revealed for the Pd2Sn:P/C catalyst compared with Pd/C. The performance improvement is rationalized with the aid of density functional theory (DFT) calculations considering different phosphorous chemical environments. Depending on its oxidation state, surface phosphorus introduces sites with low energy OH− adsorption and/or strongly influences the electronic structure of palladium and tin to facilitate the oxidation of the acetyl to acetic acid, which is considered the EOR rate limiting step. DFT calculations also points out that the durability improvement of Pd2Sn:P/C catalyst is associated to the promotion of OH adsorption that accelerates the oxidation of intermediate poisoning COads, reactivating the catalyst surface., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economía y Competitividad through the project SEHTOP, ENE2016- 77798-C4-3-R, and ENE2017-85087-C3. X. Y. thanks the China Scholarship Council for the scholarship support. J. Liu acknowledges support from the Jiangsu University Foundation (4111510011). J. Li obtained International Postdoctoral Exchange Fellowship Program (Talent-Introduction program) in 2019 and is grateful for the project (2019M663468) funded by the China Postdoctoral Science Foundation. Authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246, and from IST Austria. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. J. Llorca is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128 and to ICREA Academia program.

In this contribution, we report a totally new and an unprecedented capability of producing nano-CeO2 evenly dispersed over reduced graphene oxide (rGO), enabling an extremely high dispersion of Pd at high loading (~5%wt) in the catalyst, in one-step hydrothermal synthesis. Morphology and thermal stability of the synthesized Pd/CeO2-rGO system are compared with Pd/rGO counterpart. High-resolution transmission microscopy studies of synthesized samples combined with X-ray diffraction, Raman and thermal analyses showed the formation of sub-nanometer Pd clusters on nano-CeO2 dispersed over reduced graphene oxide (rGO). Notably, rGO had a decisive role over the stabilization of CeO2 as nano-structures, leading to the outstanding Pd dispersion on this catalyst.

Several Ni, Cu and Ni-Cu catalysts supported on mesoporous hectorite were prepared, characterized and tested for the hydrogenation of commercial furfural to obtain tetrahydrofurfuryl alcohol (THFA). The highest selectivity to THFA (95 %) for a total conversion was achieved with the Ni-Cu catalyst prepared with a Ni:Cu molar ratio of 1:1 after 4¿h of reaction. This can be explained by the formation of NiCu alloy in high amounts for this sample (88 %), as detected by XRD. The lower selectivity to THFA obtained with other bimetallic catalysts prepared with Ni:Cu molar ratios of 6:1 and 1:6 were attributed to the lower percentage of NiCu alloy together with the lowest Ni richness of the NiCu alloy. Additionally, the best catalyst resulted in a yield to THFA of 90 %, in the toluene phase, and 80 % in the aqueous neutralized phase, when using a biomass extract of furfural obtained from almond shells instead of commercial furfural. After several reuses of the catalyst employed in the toluene phase, some decrease of THFA was observed due to the increase of the crystallite size of the Cu phase, as observed by XRD, that should decorate the active NiCu alloy particles.

Graphene oxide (GO)-based nanocomposites have received a great attention due to their emerging applications. Here, we thoroughly examined the structural, electronic and surface properties of $$\hbox {GO}/\hbox {TiO}_{2}$$ nanotubes nanocomposite. The nanocomposite is prepared by simple impregnation of $$\hbox {TiO}_{2}$$ nanotubes (HNT400) with GO dispersion. GO is elaborated by an improved Hummer’s method, while HNT400 is obtained using alkaline hydrothermal treatment of $$\hbox {TiO}_{2}$$ P25, followed by calcination at $$400^{\circ }\hbox {C}$$ . XRD and Raman analyses show that GO nanosheets do not change the structural properties of $$\hbox {TiO}_{2}$$ nanotubes. TEM analysis confirms the formation of GO nanosheets assembled to $$\hbox {TiO}_{2}$$ nanotubes. XPS and EPR results confirm the electron transfer between GO and $$\hbox {TiO}_{2}$$ nanotubes. PL analysis reveals that GO inhibits the recombination of photogenerated electron–hole pairs in the nanocomposite. The ac conductivity measurements suggest the presence of grain and grain boundary effects in GO/HNT400.

Furfural has been highlighted as one of the top ten most rewarding bio-based building blocks by the US Department of Energy. In this study, furfural was produced from xylose and birch hydrolysate liquor employing a batch reactor in a biphasic system. The formation of furfural was conducted under auto-catalyzed conditions. 2-sec-Butylphenol was used as extractant to promptly extract furfural from the aqueous phase in order to minimize furfural degradation reactions. The effect of time, temperature, and organic-to-aqueous phase ratio were investigated. The maximum furfural yields from xylose and birch hydrolysate liquor as feedstock under auto-catalyzed conditions when employing 2-sec-butylphenol (SBP) were 59 mol% and 54 mol%, respectively. In the monophasic system when using hydrolysate, 46% furfural was yielded. Based on a techno-economic analysis carried out for furfural, the total investment cost for a plant integrated with an existing pulp mill or bio-refinery is estimated as 14 M€. The minimum selling price of furfural found to be 1.62 € kg−1. With a furfural selling price of 1.93 € kg−1, the payback period is approximately 5 years and an internal rate of return (IRR) of 20.7% is achieved at the end of the project lifetime.

Altres ajuts: ICN2 is funded by the CERCA. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. T.Z. has received funding from the CSC-UAB PhD scholarship program. Intermetallic PdPb nanocrystals with controlled size and cubic geometry exposing (100) facets are synthesized and tested as electrocatalysts for ethanol oxidation in alkaline media. We observe the ethanol oxidation activity and stability to be size-dependent. The 10 nm PdPb nanocrystals display the highest initial current densities, but after few hundred cycles, the current density of smaller nanocrystals becomes much larger. All of the catalysts exhibit a pronounced current decay during the first 500 s of continuous operation, which is associated with the accumulation of strongly adsorbed reaction intermediates, blocking reaction sites. These adsorbed species can be removed by cycling the catalysts or maintaining them at slightly higher potentials for a short period of time to oxidize and later reduce the Pd surface. Such simple cleaning processes, that can be performed during operation breaks without cell disassembly, is sufficient to effectively remove the poisoning species adsorbed on the surface and recover the electrocatalytic activity.

We present a simple, versatile, and scalable procedure to produce SnS2 nanostructured layers based on an amine/thiol-based molecular ink. The ratios amine/thiol and Sn/S, and the reaction conditions, are systematically investigated to produce phase-pure SnS2 planar and conformal layers with a tremella-like SnS2 morphology. Such nanostructured layers are characterized by excellent photocurrent densities. The same strategy can be used to produce SnS2–graphene composites by simply introducing graphene oxide (GO) into the initial solution. Conveniently, the solvent mixture is able to simultaneously dissolve the Sn and Se powders and reduce the GO. Furthermore, SnS2-xSex ternary coatings and phase-pure SnSe2 can be easily produced by simply incorporating proper amounts of Se into the initial ink formulation. Finally, the potential of this precursor ink to produce gram-scale amounts of unsupported SnS2 is investigated., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economía y Competitividad through the projects SEHTOP, ENE2016-77798-C4-3-R, and ENE2017-85087-C3. Y.Z. thanks the China Scholarship Council for the scholarship support (no. 201606500001). The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. J. Llorca is a Serra Húnter Fellow and is grateful to ICREA Academia program and to MINECO/FEDER grant RTI2018-093996-B-C31 and GC 2017 SGR 128. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. T.Z. has received funding from the CSC-UAB PhD scholarship program.

This research received funding from the postdoctoral fellowships programme Beatriu de Pinós (2018 BP 00146), funded by the Secretary of Universities and Research (Governement of Catalonia) and by Horizon 2020 programme of research and innovation of the European Union under the Marie Skłodowska-Curie grant agreement No 801370. A functionalized silicon micromonolith of 7 mm in diameter and 210 μm-thick was evaluated for the production of hydrogen from the steam reforming (SR) of various fuels, containing different functional groups, such as ethanol, acetic acid, 2-propanol, acetone, and 2-methoxyethanol. The micromonolith consisted of 2 million regular channels of 3.3 μm in diameter, which were coated with a 100-nm RhPd/CeO2 catalytic layer. The catalytic activity was tested at temperatures between 823 and 1023 K, using overstoichiometric steam-to-carbon ratios and operating at contact times between 0.005 and 0.009 s. The best performance was obtained for the 2-methoxyethanol SR tests, where 53% H2 selectivity was recorded. A remarkable hydrogen production normalized by reactor volume of 110 LNH2·mL2-methoxyethanol, liquid−1 cm−3Reactor was recorded, leading to comparable H2 yields to those obtained with a conventional monolith coated with the same RhPd/CeO2 catalyst, owing to the large contact area. After more than 80 h under reaction conditions, the micromonolith was characterized by SEM and TEM. SEM analyses showed that no channels were blocked due to carbon deposition nor detached CeO2 layers were found. These results demonstrate the feasibility of using catalytic Si micromonoliths as microreformers to generate hydrogen from the SR of different fuels to power portable fuel cells.

In this paper, we investigated the effect of reaction kinetics and moving bed reactors for chemical looping (CO2/H2O) splitting unit (CL) that produces syngas and fed back to the power plant to gain the efficiency loss due to carbon capture. The reduction reactor (RED) produces methane is partially oxidized to make syngas and reducing the non-stoichiometric ceria which is transported to oxidation reactor (OXI) where the flue gases (CO2 and H2O) split to produce syngas. We developed the kinetics for methane reduced ceria and CO2/H2O splitting in a tubular reactor for an operating temperature range of (900–1100 °C) for different methane concentration which yielded to Avrami-Erofeev (AE3) model fits well for both redox reaction with different reaction constants. A moving bed reactors system is developed representing RED and OXI reactors of CL unit with kinetics hooked to the model in Aspen Plus with FORTRAN code. The effect of thermodynamics and the kinetics of redox reaction was investigated in the proposed integrated plant. The CL unit efficiency obtained is 42.8% for kinetic-based CL unit compares to 64% for thermodynamic based CL unit. However, the maximum available efficiency of the proposed layout lowered as 50.9% for kinetic-based CL unit plant compare to than 61.5% for thermodynamic based CL unit. However, the proposed plant shows an improvement in the energy efficiency penalty from 11.3% to 3.8% after CCS.

To commercially realize the enormous potential of lithium–sulfur batteries (LSBs) several challenges remain to be overcome. At the cathode, the lithium polysulfide (LiPS) shuttle effect must be inhibited and the redox reaction kinetics need to be substantially promoted. In this direction, this work proposes a cathode material based on a transition-metal selenide (TMSe) as both adsorber and catalyst and a hollow nanoreactor architecture: ZnSe/N-doped hollow carbon (ZnSe/NHC). It is here demonstrated both experimentally and by means of density functional theory that this composite provides three key benefits to the LSBs cathode: (i) A highly effective trapping of LiPS due to the combination of sulfiphilic sites of ZnSe, lithiophilic sites of NHC, and the confinement effect of the cage-based structure; (ii) a redox kinetic improvement in part associated with the multiple adsorption sites that facilitate the Li+ diffusion; and (iii) an easier accommodation of the volume expansion preventing the cathode damage due to the hollow design. As a result, LSB cathodes based on S@ZnSe/NHC are characterized by high initial capacities, superior rate capability, and an excellent stability. Overall, this work not only demonstrates the large potential of TMSe as cathode materials in LSBs but also probes the nanoreactor design to be a highly suitable architecture to enhance cycle stability., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economíay Competitividad through the project SEHTOP, ENE2016-77798-C4-3-R, and ENE2017-85087-C3. D. Yang, C. Zhang, and X. Han thank the China Scholarship Council for the scholarship support. Z. Liang acknowledges funding from a MINECO SO FPI PhD grant (SEV-2013-0295-17-1). J. Li obtained an International Postdoctoral Exchange Fellowship (Talent-Introduction program) in 2019 and is grateful for the project (2019M663468) funded by the China Postdoctoral Science Foundation. The authors acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and 2017 SGR 1246. ICN2 acknowledges the support from the Severo Ochoa Programme (MINECO, grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. J. Llorca is a Serra Húnter Fellow and is grateful to MICINN/FEDER RTI2018-093996-B-C31, GC 2017 SGR 128, and to the ICREA Academia program.

The tuning of the chemical composition in nanostructures is a key aspect to control for the preparation of new multifunctional and highly performing materials. The modification of Cu2-xSe nanocrystals with Pt could provide a good way to tune both optical and catalytic properties of the structure. Although the heterogeneous nucleation of metallic Pt domains on semiconductor chalcogenides has been frequently reported, the insertion of Pt into chalcogenide materials has not been conceived so far. In this work we have explored the experimental conditions to facilitate and enhance the insertion of Pt into the Cu2-xSe nanocrystalline lattice, forming novel ternary phases that show a high degree of miscibility and compositional variability. Our results show that Pt is mainly found as a pure metal or a CuPt alloy at high Pt loads (Pt : Cu atomic ratio in reaction medium >1). However, two main ternary CuPtSe phases with cubic and monoclinic symmetry can be identified when working at lower Pt : Cu atomic ratios. Their structure and chemical composition have been studied by local STEM-EDS and HRTEM analyses. The samples containing ternary domains have been loaded on graphite-like C3N4 (g-C3N4) semiconductor layers, and the resulting nanocomposite materials have been tested as promising photocatalysts for the production of H2 from aqueous ethanolic solutions.

Tin disulfide is a promising anode material for Li-ion batteries (LIB) owing to its high theoretical capacity and the abundance of its composing elements. However, bare SnS2 suffers from low electrical conductivity and large volume expansion, which results in poor rate performance and cycling stability. Herein, we present a solution-based strategy to grow SnS2 nanostructures within a matrix of porous g-C3N4 (CN) and high electrical conductivity graphite plates (GPs). We test the resulting nanocomposite as anode in LIBs. First, SnS2 nanostructures with different geometries are tested, to find out that thin SnS2 nanoplates (SnS2-NPLs) provide the highest performances. Such SnS2-NPLs, incorporated into hierarchical SnS2/CN/GP nanocomposites, display excellent rate capabilities (536.5 mA h g−1 at 2.0 A g−1) and an outstanding stability (∼99.7% retention after 400 cycles), which are partially associated with a high pseudocapacitance contribution (88.8% at 1.0 mV s−1). The excellent electrochemical properties of these nanocomposites are ascribed to the synergy created between the three nanocomposite components: i) thin SnS2-NPLs provide a large surface for rapid Li-ion intercalation and a proper geometry to stand volume expansions during lithiation/delithiation cycles; ii) porous CN prevents SnS2-NPLs aggregation, habilitates efficient channels for Li-ion diffusion and buffer stresses associated to SnS2 volume changes; and iii) conductive GPs allow an efficient charge transport., This work was supported by the European Regional Development Funds and by the Spanish Ministerio de Economía y Competitividad through the project SEHTOP (ENE2016-77798-C4-3-R). Y.Z. thanks China Scholarship Council for scholarship support (201606500001). This work was accomplished with the financial supported from the National Natural Science Foundation of China (no. 51771076) and (no. 51621001. the Foundation for Innovative Research Groups). Jun Liu acknowledges the support from Chinese Government the young “1000 plan”, and thanks the projects of Guangzhou Science and Technology Plan (no. 201804010104) and Guangdong Province Public Interest Research and Capacity Building (no. 2017A010104004). Jordi Llorca is a Serra Húnter Fellow and is grateful to ICREA Academia program and GC 2017 SGR 128. X.H. thanks China Scholarship Council for scholarship support (201804910551). ICN2 acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project ENE2017-85087-C3-3-R. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme /Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program.

Production of fly ash zeolites may be an attractive method for the utilization of solid wastes from the energy sector. Different methods of synthesis often yield a variety of zeolite types, thereby affecting the properties of the resulting materials. The attention paid to carbon dioxide emission reduction technologies fully justifies the study of the sorption behaviours of fly ash zeolites synthesized by different methods. This work investigates the sorption properties of fly ash zeolites synthesized with different methods using CO2. Sorption capacity and adsorption isotherms were determined following the volumetric method and textural parameters were resolved according to the Dubinin-Astakhov (DA) method. The CO2 sorption capacity was in the range 0.24–4.16 mmol/g. The relationships between structure and sorption behaviour were studied for each synthesis method. Some strong similarities between commercial zeolites and fly ash zeolites were found. The mechanism for sorption was proved to be physisorption which is fully reversible under selected conditions. The observed trends were used to identify the best sorbent.

Experimental work on the carbonation of brucite has been carried out in the temperature and pressure ranges of 50-120 °C and 1-10 bar respectively, using concentrated CO2 and simulated flue gas. At 120 °C hydro- magnesite and trace amounts of magnesite were identified. Highly to semi-ordered dypingite like-phases and nesquehonite, coexisting with a possibly amorphous carbonate phase, were identified at 50 °C. The dehydration temperatures and chemical composition of these amorphous phases are very close to those of crystalline, stoi- chiometric nesquehonite. This probably amorphous phase nourishes the late formation of dypingite. This latter mineral gradually undergoes a cell shrinkage due to the partial loss of molecular waters, becoming structurally more ordered as the carbonation reaction proceeds. It remains unclear whether nesquehonite formed directly from brucite or from the crystallization of an amorphous precursor. However, nesquehonite is precursor of dypingite and/or the possibly amorphous phase. Only crystalline carbonate phases were observed at 120 °C. Concentrated CO2 experiments yielded the highest amounts (up to 37 wt.%) of CO2 sequestered at 10 bar and 16 h of reaction, reaching an almost complete carbonation of brucite (> 98 %). On the other hand, flue gas experiments results showed higher amounts of CO2 sequestered per unit of CO2 partial pressure than with concentrated CO2.

In this contribution we synthesized ternary CuGaS2-TiO2-Pt materials. The semiconductor components were surface functionalized with mercapto-alifatic acids to drive their linking and were platinized prior to or after contact between the semiconductors. The corresponding samples were utilized in the photo-production of hydrogen using methanol as a sacrificial agent. The testing under UV and visible illumination conditions together with the calculation of the true quantum efficiency of the process demonstrate the outstanding performance of these ternary materials under sunlight operation. Optimum activity was achieved for samples having a 3 to 5 wt % of the chalcogenide and a selective interaction of the noble metal with the major oxide component. The physico-chemical characterization and particularly the use of photoluminescence spectroscopy showed that photo-activity is controlled by charge separation under illumination, which drives to charge location of electrons and holes in different components of the powders and the efficient use of charge carriers in the chemical reaction.

Altres ajuts: Catalan Institute of Nanoscience and Nanotechnology (ICN2) is funded by the CERCA Programme/Generalitat de Catalunya. H.X. and T.Z. thank the CSC-UAB PhD scholarship program. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. Monodisperse CoSn and NiSn nanoparticles were prepared in solution and supported on commercial carbon black. The obtained nanocomposites were applied as anodes for Li- and K-ion batteries. CoSn@C delivered stable average capacities of 850, 650, and 500 mAh g-1 at 0.2, 1.0, and 2.0 A g-1, respectively, well above those of commercial graphite anodes. The capacity of NiSn@C retained up to 575 mAh g-1 at a current of 1.0 A g-1 over 200 continuous cycles. Up to 74.5 and 69.7% pseudocapacitance contributions for Li-ion batteries were measured for CoSn@C and NiSn@C, respectively, at 1.0 mV s-1. CoSn@C was further tested in full-cell lithium-ion batteries with a LiFePO4 cathode to yield a stable capacity of 350 mAh g-1 at a rate of 0.2 A g-1. As electrode in K-ion batteries, CoSn@C composites presented a stable capacity of around 200 mAh g-1 at 0.2 A g-1 over 400 continuous cycles, and NiSn@C delivered a lower capacity of around 100 mAh g-1 over 300 cycles.

Carbonation of industrial wastes rich in earth-alkali oxides is found to have a significant potential for CO2 sequestration. This process opens new perspectives not only for carbon dioxide mitigation, but also for the valorization and new applications of industrial waste materials from coal-burning power plants. In this study, mineral carbonation of high–calcium fly ash is investigated under dry and moist conditions in a continuous flow reactor during up to 2 h, at temperatures ranging from 160 to 290 °C and CO2 pressures between 1 and 6 bar. A comprehensive characterization of treated and untreated samples was carried out before and after carbonation using X-ray diffraction, X-ray fluorescence spectroscopy, thermogravimetric analysis, infrared spectroscopy and scanning electron microscopy. The maximum sequestration capacity achieved was 117.7 g CO2/kg fly ash (48.14% carbonation efficiency) under dry conditions. Results showed that increasing the pressure and temperature enhances the process of carbonation, as well as the presence of moderate amounts of water vapor in the CO2 gas flow. Newly formed carbonates were always present in the treated samples. This study shows that about 21% of all CO2 emissions of a coal-burning power plant could potentially be sequestered as carbonates.