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Safety plays an important role in determining the applicability of energetic compounds, and the bond dissociation enthalpy (BDE) of the “trigger bond” X-NO2 provides useful information to evaluate various safety properties. Accurate and rapid calculation of the BDE of X-NO2 is of great significance to perform the high-throughput design of energetic compounds, which becomes an increasingly popular means of materials design. We conduct a benchmark BDE calculation for 44 X-NO2 samples extracted from the iBond database, with the accuracies of 55 quantum chemistry calculation levels evaluated by the experimentally measured values. Only four levels have the global mean-absolute deviation (MAD) less than 10 kJ/mol, but no calculation level can achieve that all the local MADs of each category less than 10 kJ/mol. We propose a simple correction strategy for the original calculation deviations, and apply it to 30 calculation levels screened out through a series of accuracy assessments and obtain the corrected MAD

The cognition of active sites in the Ni-based catalysts plays a vital role and remains a huge challenge in improving catalytic performance of low temperature CO2 dry reforming of methane (LTDRM). In this work, typical catalysts of SiO2 and γ-Al2O3 supported Ni and Ni-Ce were designed and prepared. Importantly, the difference in the chemical speciations of active sites on the Ni-based catalysts is revealed by advanced characterizations and further estimates respective catalytic performance for LTDRM. Results show that larger [ Ni n 0 ] particles mixed with [Ni-O-Sin]) species on the Ni/SiO2(R) make CH4 excessive decomposition, leading to poor activity and stability. Once the Ce species is doped, however, superior activity (59.0% CH4 and 59.8% CO2 conversions), stability and high H2/CO ratio (0.96) at 600 °C can be achieved on the Ni-Ce/SiO2(R), in comparison with other catalysts and even reported studies. The improved performance can be ascribed to the formation of integral ( [ Ni n 0 ] -[CeIII-□-CeIII]) species on the Ni-Ce/SiO2(R) catalyst, containing highly dispersed [ Ni n 0 ] particles and rich oxygen vacancies, which can synergistically establish a new stable balance between gasification of carbon species and CO2 dissociation. With respect to Ni-Ce/γ-Al2O3(R), the Ni and Ce precursors are easily captured by extra-framework Aln-OH groups and further form stable isolated ( [ Ni n 0 ] -[Ni-O-Aln]) and [CeIII-O-Aln] species. In such a case, both of them preferentially accelerate CO2 adsorption and dissociation, causing more carbon deposition due to the disproportionation of superfluous CO product. This deep distinguishment of chemical speciations of active sites can guide us to further develop new efficient Ni-based catalysts for LTDRM in the future.

Although the direct synthesis of hydrogen peroxide (DSHP) is a potential alternative to the current anthraquinone auto-oxidation process, the low H2O2 selectivity of the former presents a major challenge. Previous studies have reported that the addition of halides improves the H2O2 selectivity of Pd-based catalysts. In this study, the H2O2 selectivity of Pd/SiO2 and PdBrx/SiO2 catalysts was observed to increase with the Br content. Furthermore, density functional theory (DFT) calculations on clean and Br-adsorbed Pd (1 1 1), (1 0 0), and (2 1 1) surfaces confirmed that the activation energies of the side reactions on the Pd (1 1 1) surface increased slightly after Br adsorption, whereas those of the main reactions were less affected. The repulsion between Br and O on the Pd (1 0 0) surface increased the O2 dissociation barrier by changing reaction configurations. Considering that the Pd (1 0 0) surface adsorbed O2 more strongly than did the Pd (1 1 1) surface, inhibiting O2 dissociation on the Pd (1 0 0) surface improved the H2O2 selectivity of PdBrx/SiO2 catalysts. On the Pd (2 1 1) surface, Br blocked an edge site and induced the reactions on the Pd (1 1 1) surface. In conclusion, DFT calculation confirmed that the repulsion and site blocking by adsorbed Br improved the H2O2 selectivity of PdBrx/SiO2 catalysts.

The catalytic properties of bifunctional ZSM-5@t-ZrO2 catalyst for methanol thiolation were revealed by using methanol and H2S as probe molecules. Taking the ZSM-5/t-ZrO2 physically-blended catalyst, pure ZSM-5 and t-ZrO2 as control catalysts, we investigated the characteristics of adsorption and transformation of different reaction molecules on or over different catalysts by combination of in-situ diffuse reflectance Fourier transform infrared spectroscopy (Drifts) and a variety of techniques including XRD, XPS, XRF, FT-IR, N2 adsorption-desorption, CO2/NH3-TPD, and DSC. The results showed that the synergistic effect of acid sites between ZSM-5 phase and t-ZrO2 phase in the bifunctional catalyst enhanced the adsorption and dissociation of methanol molecules, while the base sites in t-ZrO2 phase were mainly responsible for the adsorption and dissociation of H2S molecules. Due to the small specific surface area of pure t-ZrO2 catalyst, precursor species for sulfur deposition and carbon deposition were easily formed. Presulfurization could improve the initial activity of methanol thiolation and shorten the induction period. The dissociation of H2S at the base sites was the rate-determining step of the bimolecular reaction, and the appropriate increase of base sites in the bifunctional components could construct the matching formation rate of sulfhydryl and methoxy groups. At the same time, the special composite structure and meso-microporous system of ZSM-5@t-ZrO2 could effectively reduce the formation rate of carbon and sulfur deposits.

International audience; The mechanisms of H 2 dissociation on three stoichiometric anatase TiO 2 terminations, (001), (100) and (101), have been studied by means of density functional theory (PBE+U) calculations. A two-step process was considered: first, H 2 dissociation into H + and H − pair, and second the H − species migrates to a neighboring O site, transferring the electrons to the substrate. On (001), it shows the lowest activation barriers for hydrogen dissociation, 0.37 eV, whereas the highest value was found on (101), 0.98 eV. For hydrogen transfer from Ti to near O, the activation barriers are higher (from 1.10 to 2.37 eV), which indicates the dissociation step is kinetically more favorable than the H transfer process, although the latter is thermodynamically more favorable. Electronic structure, vibrational frequency analysis as well as temperature effects are studied to characterize the reactivity. The relationship between electronic structure, geometry and reactivity is analyzed by means of reactivity descriptors, and the results are compared with ceria and rutile TiO 2 facets.

Along this research the (110), (101) (200) and (211) surfaces were chosen to be studied by considering their atomic surface density. The surfaces were studied using CASTEP for the transition state search by DFT calculations, the initial coordinates that establish the SnO2-Methane distance were obtained with Adsorption Locator, a software able to calculate adsorption configurations using Monte Carlo methods. The results show that in terms of overall energy change, surface (101) presents the most favorable configuration with an exothermic total-energy change (form CH4 on the surface to a CO and H2O molecules on the surface) of − 18.47 kcal/mol, being the worst case the CH4 on a (200) surface with an endothermic total energy-change of 128.86 kcal/mol. In terms of the TS energy, the (101) surface remains as the most favorable system with energy maximums on the TS reaction path of 99.25 kcal/mol for the dissociation and adsorption of the CH4 molecule on the surface, and a maximum of 266.42 kcal/mol for the desorption and formation of the CH4 and H2O molecules on the SnO2 surface.

Ni-Al mixed metal oxides have been successfully prepared by high shear mixer (HSM) and coprecipitation (CP) methods for low temperature CO methanation. In this work, Ni-Al (HSM-CP) catalyst presented small Ni crystallite size and high surface area, which all contribute to the methanation reaction at low temperature conditions. The obtained Ni-Al (HSM-CP) sample exhibited a mass of defective oxygen, thereby accelerating the dissociation of CO and ultimately increasing the activity of the catalyst. Ni-Al (HSM-CP) catalyst offered the best activity with CO conversion=100 % and CH4 selectivity=93 % at 300 ℃, and the CH4 selectivity can reach 81.8 % at 200 °C. In situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) show that CHO and COH intermediates with lower activation energy barriers are produced during the reaction, and hydrogen-assisted carbon-oxygen bond scission is more favorable.

Density functional theory (DFT) calculations have been performed to investigate the hydrogen dissociation and diffusion on Mg (0001) surface with Ni incorporating at various locations. The results show that Ni atom is preferentially located inside Mg matrix rather than in/over the topmost surface. Further calculations reveal that Ni atom locating in/over the topmost Mg (0001) surface exhibits excellent catalytic effect on hydrogen dissociation with an energy barrier of less than 0.05 eV. In these cases, the rate-limiting step has been converted from hydrogen dissociation to surface diffusion. In contrast, Ni doping inside Mg bulk not only does little help to hydrogen dissociation but also exhibits detrimental effect on hydrogen diffusion. Therefore, it is crucial to stabilize the Ni atom on the surface or in the topmost layer of Mg (0001) surface to maintain its catalytic effect. For all the case of Ni-incorporated Mg (0001) surfaces, the hydrogen atom prefers firstly immigrate along the surface and then penetrate into the bulk. It is expected that the theoretical findings in the present study could offer fundamental guidance to future designing on efficient Mg-based hydrogen storage materials.

Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/ O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (kapp) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation.

Nickel molybdate (NiMoO4) attracts superior hydrogen desorption behavior but noticeably poor for efficiently driving the hydrogen evolution reaction (HER) in alkaline media due to the sluggish water dissociation step. Herein, we successfully accelerate the water dissociation kinetics of NiMoO4 for prominent HER catalytic properties via simultaneous in situ interfacial engineering with molybdenum dioxide (MoO2) and doping with phosphorus (P). The as-synthesized P-doped NiMoO4/MoO2 heterostructure nanorods exhibit outstanding HER performance with an extraordinary low overpotential of −23 mV at a current density of 10 mA cm−2, which is highly comparable to the performance of the state-of-art Pt/C coated on nickel foam (NF) catalyst. The density functional theory (DFT) analysis reveals the enhanced performance is attributed to the formation of MoO2 during the in situ epitaxial growth that substantially reduces the energy barrier of the Volmer pathway, and the introduction of P that provides efficient hydrogen desorption of NiMoO4. This present work creates valuable insight into the utilization of interfacial and doping systems for hydrogen evolution catalysis and beyond.

CO2 electroreduction reaction (CO2RR), combined with solid oxide electrolysis cells (SOECs), is a feasible technology for the storage of renewable electric energy, while its development is limited by the catalytic activity and stability on cathodes. Here, a novel garnet oxide (Gd3Fe5O12) cathode is designed, where the garnet oxide is converted to perovskite oxide and iron via in situ electrochemical phase transition during CO2 electroreduction, resulting in high activity with Faradaic efficiency close to 100% and great stability over 1000 h galvanostatic test. A variety of experimental characterizations and density functional theory calculations indicate that in situ exsolved Fe clusters can effectively enhance the adsorption energies of intermediates and lowering the CO2 dissociation barriers. Microkinetic modelling confirms that CO2RR goes through a dissociative adsorption mechanism and the electronic transfer for CO2 dissociation is the rate-determining step.

Summary Although advances in coating technologies have allowed us to match—or even exceed—the lubricity of Nature’s low-friction surfaces, the performance of synthetic materials inevitably diminishes over time as the surfaces are worn and damaged by irreversible breakage of covalent bonds. Synthetic systems lack the bespoke repair mechanisms that replenish hydration lubrication surfaces in Nature. Here, we demonstrate dynamic repair of low-friction surfaces prepared through a surface-selective self-assembly strategy. Monolayers of lubricating polymers associate with functionalized surfaces through strong and specific host–guest interactions, leading to hydration lubrication surfaces with low coefficients of friction (0.024–0.028). Following friction-induced dissociation of the polymers, the polymer-to-surface interaction is restored by the reformation of host–guest complexes, thus repairing the monolayer, renewing the lubricity, and reducing the effects of wear. Such dynamically restored low-friction materials will be an essential tool in decreasing global energy use—a fifth of which is expended overcoming friction.

SrFeO3-δ perovskite material is considered as a potential substitute for Ni-based fuel electrodes, while the problem of Sr segregation limits the development of material. Herein, different high-valence elements Ti4+, Nb5+and Mo6+ are gradient doped into La0.5Sr0.5FeO3-δ (LSF) to solve Sr segregation and study the influence mechanism for high valence elements. After the LSF is doped by high-valence elements, the reduction stability and CO2 tolerance are found to be obviously improved in a CO2:CO = 1:1 atm. Under the premise of stability, lower-valence element doping requires less Fe4+ reduction and lattice oxygen to match the charge, therefore, La0.5Sr0.5Fe0.9Ti0.1O3-δ (LSFTi5591) possesses more oxygen vacancies than La0.5Sr0.5Fe0.9Nb0.1O3-δ (LSFNb5591) and La0.5Sr0.5Fe0.9Mo0.1O3-δ(LSFMo5591). Since Ti ions possess a weaker binding force with O ions, LSFTi5591 more easily loses lattice oxygen and generates oxygen vacancies under high-temperature and reduction conditions, which results in stronger CO2 adsorption. Using LSCF-GDC as the oxygen electrode of electrolytic cells, the LSFTi5591 cell (1.35 A cm−2) exhibits higher electrochemical performance than LSFNb5591 (1.18 A cm−2) and LSFMo5591 (1.04 A cm−2) cells due to stronger CO2 adsorption and dissociation in the medium-frequency resistance range.

We have prepared well-resolved Nb n + (n = 1–10) clusters and report here an in-depth study on the essentially different reactivity with N2 and O2, by utilizing a multiple-ion laminar flow tube reactor in tandem with a customized triple quadrupole mass spectrometer (MIFT-TQMS). As results, the Nb n + clusters are found to readily react with N2 and form adsorption products NbnN 2 m + ; in contrast, the reactions with O2 give rise to NbnO 1 − 4 + products, and the odd-oxygen products indicate O-O bond dissociation, as well as increased mass abundance of NbO+ pertaining to oxygen-etching reactions. We illustrate how N2 prefers a physical adsorption on Nb n + clusters with an end-on orientation for all the products, and allow for size-selective Nb n + clusters to act as electron donor or acceptor in forming NbnN 2 m + . In contrast to these nitrides, the dioxides Nb n O 2 + display much larger binding energies, with O2 always as an electron acceptor, corresponding to superoxide or peroxide states in the initial reactions. Density-of-states and orbital analyses show that the interactions between Nb n + and O2 are dominated by strong π-backdonation indicative of incidental electron transfer; whereas weak π-backdonation and simultaneous σ donation interactions exist in Nb n N 2 + . Further, reaction dynamics analysis illustrates the different interactions for N2 and O2 in approaching the Nb n + clusters, showing the energy diagrams for N2 adsorption and O-O bond dissociation in producing odd-oxygen products. Fragment analyses with orbital correlation and donor-acceptor charge transfer are also performed, giving rise to full insights into the reactivities and interactions of such transition metal clusters with typical diatomic molecules.

Hypothesis Dynamic imine surfactants (DIS) can be constructed by the formation of dynamic imine bonds (Dibs) between aromatic aldehydes and aliphatic amines in water. Because of the nature of Dibs in water, a thermodynamic equilibrium state was achieved between the DIS and aldehyde and amine precursors to form a dynamic combinatorial library (DCL). When the DIS served as sole emulsifier to form oil–H2O emulsions, the precursors migrated between the H2O phase and the oil phase, which altered the DCL equilibrium. The DIS concentration and emulsion stability also changed. Experiments By mixing 4-(2-sulfobetaine-ethoxy)-benzaldehyde (SBBA) and aliphatic amines of CnH2n+1NH2 (n = 4, BA; n = 6, HA; n = 8, OA; n = 10, DA) in water, four amphoteric DIS (SBBA–BA/HA/OA/DA) were prepared. Dib formation was characterized using 1H NMR. The DIS surface activity was studied by surface tension and fluorescence probe methods. The reversible switching of DIS and its wormlike micelles were explored. Findings SBBA–OA (or SBBA–DA) DIS was not a suitable emulsifier for stable hydrocarbon (HC)–H2O emulsions. OA and DA were more soluble in the HC phase than the H2O phase. The precursors of OA and DA migrated from the H2O to the HC phase, and the thermodynamic equilibrium state of DCL shifted towards Dib dissociation. The Dib could be regenerated by HC phase removal. A novel strategy where volatile HC (such as pentane) was used as a trigger was developed to switch the DIS reversibly and its self-assemblies (such as wormlike micelles) in water without inorganic salt accumulation. The SBBA–HA (or SBBA–BA) DIS was a suitable emulsifier for stable emulsions because HA and BA were more soluble in the H2O phase.

In this study, Co2P/CoP hybrid nanoparticles (NPs) imbedded on the surface of core-shell metal-organic frameworks (MOFs) derived three-dimensional N, P co-doped graphitized carbon (Co2P/CoP@NPGC) are prepared via direct pyrolysis of P-containing MOF precursors. P dopant dosage is tailored to adjust active sites and crystalline phases of Co2P/CoP@NPGC. The active Co2P and CoP NPs and the synergistic effect from the Co-Nx/C and Co-P/C active sites and porous NPGC make the dominant contributions to the ORR/OER. For ORR, the half-wave potential of Co2P/CoP@NPGC-1 is 0.93V, which is superior to that of Pt/C (E1/2 = 0.875 V). As for OER, Co2P/CoP@NPGC-1 displays a lower overpotential (ƞ = 340 mV) compared to RuO2 (ƞ = 380 mV, at 10 mA cm-2). The Co2P@CoOOH heterojunction guarantees intrinsic conductivity. Furthermore, doping with N and P can modify the surface electronic structure of catalyst to lower the energy of oxygen adsorption and dissociation, which are beneficial to enhance the ORR and OER activity. Additionally, its bifunctional activity parameter (ΔE) for ORR and OER is only 0.64 V, which is lower than that of Pt/C and RuO2 (0.76 V). Therefore, this work proposes a new sight into constructing a competitive core-shell MOFs derived electrocatalyst for ORR/OER.

Design of the catalyst for efficient water dissociation and hydrogen recombination is paramount in enhancement of the alkaline water electrolysis kinetics. Herein, we reported a delicate hierarchical (VO)2P2O7-Ni2P@NF (VPO-Ni2P@NF) hybrid catalyst that operated efficiently in alkaline media. The VPO and Ni2P respectively act as the water dissociation promoter and the hydrogen recombination center, which synergistically propel water adsorption/dissociation and H intermediates recombination. The resulting synergistic interfaces between VPO and Ni2P are verified to afford the catalyst an outstanding performance for hydrogen evolution reaction in alkaline media with an overpotential of 154 mV at 10 mA cm−2, Tafel slope of 65 mV dec−1, and remarkable durability. Furthermore, the catalyst presents the potential for overall water splitting. This work may shed fresh light on the high-performance electrocatalyst design and the application of VPO on water electrolysis.

A Single-Event MicroKinetic (SEMK) model has been extended towards the simulation of Steady State Isotopic Transient Kinetic Analysis (SSITKA) data for Co catalyzed Fischer-Tropsch Synthesis (FTS). The extended model considers two types of sites and both direct and H-assisted CO dissociation. Regression of the model parameters to the data obtained from 17 steady state and 11 SSITKA experiments resulted in physicochemically meaningful estimates for the activation energies and atomic chemisorption enthalpies. The application of the phenomenological UBI-QEP method allows to physically interpret the nature of the two site types considered in the model, i.e., terrace and step sites. A reaction path analysis shows that over 80 percent of the CO reacts on the step sites. Furthermore, chain growth exclusively occurs on these sites. The terrace sites are less reactive for CO dissociation and are identified as responsible for methane production. A fraction of the alkenes, produced on the step sites, is hydrogenated to alkanes on the terrace sites. Based on model simulations, the metal particle size effect, i.e., a lower TOF, higher methane selectivity and increasing alkane to alkene ratio with decreasing metal particle size, is attributed to an increasing relative importance of the terrace sites on the reaction kinetics.

In this work, we have performed density functional theory (DFT) calculations to investigate the methanol electro-oxidation reaction (MOR) catalyzed by the Pt, PtCu alloy and Cu. The complex reaction networks, including the intermediate dehydrogenation, water dissociation and anti-poison reaction steps, are systematically investigated to explore the mechanisms. At the standard condition of pH = 0 and zero potential, for Cu, most dehydrogenation steps along the favorable pathway are endergonic, making it less active in MOR. For the Pt and PtCu alloy, their dehydrogenation steps are mainly exergonic, but the formed CO intermediate binds too tightly on Pt, that can accumulate on active sites to poison the electro-catalyst. The CO can be consumed by the thermodynamic reaction with OH*, which comes from water dissociation. DFT calculation shows alloying the Pt with Cu could not only reduce the free energy barrier for binding between CO* and OH*, but also assist the water dissociation to produce more OH* for that anti-poison reaction. That makes the PtCu alloy more active than the pure Pt electrode in experiment. The results reveal the importance of anti-poison reaction and water dissociation in MOR, which could be applied to the rational design of more active alloy electro-catalysts in future.

How to utilize inexhaustible solar light as a means of disinfection technology for its cheap and green remains a challenge. In this work, core-shell ZnO@ZIF-8 was synthesized and used for bacterial inactivation synergizing with peroxymonosulfate (PMS) under visible light irradiation. It took 50 min to achieve thorough sterilization for 7.5-log {\it{Escherichia coli (E. coli)}} cells in vis/PMS/ZnO@ZIF-8 system, compared with that 4.5-log reduction completed in Vis/PMS/ZnO system under the same conditions. The enhanced photocatalytic disinfection mechanisms of fabricated ZnO@ZIF-8 were investigated by UV–vis diffuse reflectance spectra, electrochemical impedance spectra and Mott-Schottky plots. The promoted bactericidal efficiency was attributed to higher charge-separation efficiency and stronger oxidation ability of photo-generated holes. Moreover, it was found that 1O2 and •OH induced bacterial cell lesion process, and the former was the main active species. The external reactive oxygen species (ROS) caused a series of cell wall damage, intercellular ROS up-regulation and genome DNA unwinding, finally resulted in irreversible bacterial death. A two-route mechanism in vis/PMS/ZnO@ZIF-8 system was proposed, in which the generation of 1O2 was supposed as the product of the oxygen oxidation of photo-generated holes and PMS dissociation. Our work is expected to provide advanced information about a low-cost water disinfection technology of visible light photocatalysis.

To understand the microscopic mechanism of the CO oxidation reaction at PtCu nanoparticles, which have unique geometric and electronic structures compared to their component metals, we present here a theoretical study, based on density functional theory calculations, of the main reaction steps of this reaction. We examine the O2 dissociation, the CO adsorption and the CO + O2 reaction at an atomic level and use the computed geometries, Bader charges, and vibrational frequencies to rationalize the role of the intermetallic nanoparticles surface structure on the experimentally observed much higher activity of these nanoparticles as catalysts of the preferential oxidation of CO. By comparing with clean Pt (111) surface and with different Cu-doped models of this same surface, our results show that, at the surface, the presence of Cu induces the segregation of CO molecules at Pt sites and of O2 molecules at Cu sites. Contrarily to Pt surfaces, the unassisted O2 dissociation has a high barrier at the intermetallic nanoparticle surface and proceeds through a CO-assisted mechanism in which the new CO bond is formed while the O O bond is broken with a kinetic barrier much lower than on either Pt (111) or in Pt-doped surfaces. The particular structure of the intermetallic surface is shown to have a significant role in the low kinetic barrier for the reaction, allowing for an easy approach of the CO to the adsorbed O2 molecule that permits an early transition state with a low energetic barrier.

The reactions of cerium in hydrogen mixed with different concentrations of CO2 were conducted by using a pressure-volume-temperature (PVT) method combined with an in situ hot-stage microscope. CO2 has a great suppression effect on the hydriding reaction of cerium. The existence of CO2 leads to longer induction time, less pitting, and much slower hydriding rate. It is found that the induction time of hydriding reaction grows exponentially as a function of CO2 concentrations. Besides, the nucleation and growth of hydride spots are also suppressed with increase of CO2 concentrations. Scanning electron microscopy (SEM) and in situ optical microscope measurements reveal that the hydride spots formed in H2-CO2 mixture have a prolate hemispherical morphology while the normal hydride spots formed in pure H2 show an oblate hemispherical morphology. Thermal desorption results indicate CO2 preferentially adsorbs on the active sites of CeO2 surface resulting in block of hydrogen dissociation, which is accountable for the observed hydriding inhibition phenomenon. Our studies provide new insights into the CO2 effect on the hydriding process of active metals.

It is important to consider the synergy of heterostructures to improve the slow kinetics of water dissociation in the alkaline hydrogen evolution reaction (HER). Herein, we report a simple method to design a heterohierarchical CoMo catalyst. The CoMo catalyst was prepared by simple one-pot electrodeposition on carbon paper (CP). The CoMo/CP catalyst was optimized for the alkaline HER by controlling the electrodeposition bath conditions, potential, and time. The optimized catalyst shows the heterohierarchical structure containing the electrically conductive metallic Co in the bulk and Mo-incorporated Co containing Mo4+ at the surface. It exhibited a lower HER overpotential of 0.11 V at −20 mA/cm2 compared to those of the others owing to the synergetic effect of the between the Co and Mo incorporated Co. The results highlight the advantages of the simple method developed herein for the design of heterohierarchical catalysts.

Carbonate-modified metal-support interfaces allow Ru/MnCO3 catalyst to exhibit over 99% selectivity, great specific activity and long-term anti-CO poisoning stability in atmospheric CO2 methanation. As a contrast, Ru/MnO catalyst with metal-oxide interfaces prefers reverse water–gas shift rather than methanation route, along with a remarkably lower activity and a less than 15% CH4 selectivity. The carbonate-modified interfaces are found to stabilize the Ru species and activate CO2 and H2 molecules. Ru-CO* species are identified as the reaction intermediates steadily formed from CO2 dissociation, which show moderate adsorption strength and high reactivity in further hydrogenation to CH4. Furthermore, carbonates of Ru/MnCO3 are found to be consumed by hydrogenation to form CH4 and replenished by exchange with CO2, which are in a dynamic equilibrium during the reaction. Modification with surface carbonates is proved as an efficient strategy to endow metal-support interfaces of Ru-based catalysts with unique catalytic functions for selective CO2 hydrogenation.

International audience; The attachment and dissociation of a proton from a water molecule and the proton transfers at solidliquid interfaces play vital roles in numerous biological, chemical processes and for the development of sustainable functional materials for energy harvesting and conversion applications. Using first-principles computational methodologies, we investigated the protonated forms of polyhedral oligomeric silsesquioxane (POSS-H+) interacting with water clusters (Wn, where n = 1-6) as a model to quantify the proton conducting and localization ability at solid-liquid interfaces. Successive addition of explicit water molecules to POSS-H+ shows that the assistance of at least three water molecules is required to dissociate the proton from POSS with the formation of an Eigen cation (H9O4+), whereas the presence of a fourth water molecule highly favors the formation of a Zundel ion (H5O2+). Reaction pathway and energy barrier analysis reveal that the formation of the Eigen cation requires significantly higher energy than the Zundel features. This confirms that the Zundel ion is destabilized and promptly converts in to Eigen ion at this interface. Moreover, we identified a Grotthuss-type mechanism for the proton transfer through a water chain close to the interface, where symmetrical and unsymmetrical arrangements of water molecules around H+ of protonated POSS-H+ are involved in the conduction of proton through water wires where successive Eigen-to-Zundel and Zundel-to-Eigen transformations are observed in quick succession.

Identifying the characteristic properties of gas hydrates – including thermo-physical properties – is essential for determining their formation condition and in turn, controlling their yield/growth-rate for/in various applications/environments. Gathering these properties, during in-situ crystallization of gas hydrates, is rather challenging due to the harsh conditions they form and limited by the lack of co-existence of multiple characterization techniques. Owing to these limitations, crystallization process of some sII type gas hydrates and their characteristic properties are ill-defined. Therefore to unveil the complete picture of crystallization process of sII type gas hydrates, in this study, in-situ formation of a model system “cyclopentane hydrate” was monitored using a customized DSC sample holder with a transparent window on top. To this end, in-situ crystallization of cyclopentane hydrate was simultaneously followed by coupling optical microscopy along with scanning calorimetry. Further, we show that the cyclopentane hydrate formed by consuming a part of fresh water appearing after the fusion of ice instead of at a very low temperature ≤ −20 °C.

The photo-catalyzed oxidation process of Brown HT dye was studied in the aqueous solution of the dye, using an irradiation source (ultraviolet rays UV) with the use of manganese oxide (MnO) and nickel oxide (NiO) catalysts, where the effect of increasing the weight of the catalyst in the range of 0.05–0.8 g was studied using a fixed concentration of dye 20 ppm, The best weight gave the highest dissociation rate of the dye 0.1 g from MnO and 0.075 g from NiO, and at the best weight the effect of many factors on it was studied, including pH, change of initial dye concentration, and temperature. The effect of changing the pH in the range (2–10) was studied, and the best pH gave the highest rate of dissociation of the dye at pH = 2 in the presence of MnO and pH = 4 in the presence NiO when using UV as an irradiation source. The effect of changing the initial concentration of the dye in the range of 10–50 ppm was studied, as the higher the concentration, the lower the dissociation rate. Accordingly, there is an inverse relationship between the initial concentration and the dissociation rate. The effect of changing the temperature in the range (298–323) K was studied. It was found that the higher the temperature, the greater the dissociation rate. Accordingly, the relationship is direct between temperature and reaction speed, and the activation energy for each reaction was calculated using the Arrhenius equation.

Alkali metals are commonly used to promote heterogeneous catalysts. For instance, K can enhance the MoS2-catalyzed synthesis of methanethiol, an important industrial chemical, from CO/H2/H2S. Herein, we not only demonstrate that the synergy increases with alkali cation size (Cs > Rb > K > Na) but also that alkali sulfides themselves are the active sites. The alkali-normalized methanethiol formation rate of Cs sulfide is nearly the same as that of Cs-promoted MoS2 with a much lower yield of unwanted methane. Kinetic measurements show that methanethiol on alkali sulfides is formed via the reaction 3 CO + 2 H2S → COS + CO2 + CH3SH. This represents a first example of H2S as a hydrogen donor for the formation of the thiol counterpart of methanol. The role of MoS2 is that of a promoter that disperses alkali and provides spillover H from H2 dissociation.

The supported metal catalysts are usually prepared and widely applied in aqueous phase. Here, by performing density functional theory calculations and ab initio molecular dynamics simulations with explicit solvent waters, the metal-support interaction of Pd@ZrO2 catalyst was found to be enhanced by water dissociation at the metal-support interface. This happens to an appreciable number of interfacial waters, generating ∼ 25% hydrides compared to Pd atoms. After the partially heterolytic water dissociation, the generated Hδ+ would undergo the proton coupled electron transfer (PCET) from Pd to form the hydride (Hδ-). The spatial separation of the generated H on Pd and remaining OH on ZrO2 results in the polarization of metal-support interface, which then flattens the shape of cluster. Moreover, the formed metal-hydride behaves as the new catalytic active phase for CO oxidation, making the catalyst highly active in water vapor.

Natural gas hydrate is a kind of clean energy with huge reserves, and the saturation (volume percentage of hydrate in pore space of sediments) is the key parameter for determining whether the reservoir is worthy of exploitation. In this work, rapid hydrate dissociation by the combination of heat injection and NaCl inhibitor addition was studied, and an on-site evaluation method for hydrate saturation in sediment samples was proposed by using a core sampler to transfer hydrate samples under pressure. The results showed that the average gas production rate per unit volume was increased significantly to reach 7.22 L/Lr·min-1 by the injection of NaCl aqueous solution with 50.9 °C, which was attributed to the increase of the chemical potential to further accelerate the rate of hydrate dissociation in the presence of NaCl. Furthermore, for the measurement of methane hydrate samples saturation with a volume of 673 cm3 (which contained 1.4 mol hydrates with the saturation of 58%), hydrate saturation could be accurately achieved within 30 min with a relative error lower than 11.7% This work may provide new thoughts for on-site saturation evaluation and rapid dissociation of hydrate samples during natural gas hydrate exploitation.

n-Butyl levulinate (n-BL) has numerous applications in biofuel and green solvents. In this paper, we have reported mechanistic accounts of sonoenzymatic synthesis of n-BL using Novozym 435. Esterification parameters were optimized with statistical design of experiments. Application of 35 kHz sonication boosted n-BL yield from 70.9% to 92.22%. Mechanistic investigation using Ping-Pong Bi-Bi kinetics model and molecular docking simulations revealed interesting influence of sonication on esterification reaction. Exposure to sonication induced significant changes in the secondary structure of enzyme, as revealed in ATR-FTIR analysis. Sonication increased α-helix content of enzyme that increased enzyme activity by opening of flapping lid and widening the catalytic cavity. Sonication also caused unfolding of secondary structural motifs with rise in random coil content that favored formation of enzyme-ligand complexes. These effects enhanced reaction velocity and substrate affinity with reduction in inhibition and unfavorable dissociation of intermediate complexes, which ultimately enhanced n-BL yield.

The rare-earth metal Gd plays an important role in the energy, information, and national defence fields due to its special optical, electrical, magnetic, and catalytic properties. In this study, Gd was purified by direct current (DC) arc plasma, and Gd2O3 nanoparticles were prepared via an integration method using purified Gd. The effects of arc current, melting time, gas pressure, and atmosphere on the purification of Gd by DC arc plasma were investigated. With an increase in the arc current and melting time, the rate of removal of impurities from Gd enhances. Moreover, Gd melting was conducted by H2–Ar arc plasma, which improves the impurity removal rate by increasing the H2 content. High thermal conductivity and chemical activity of the activated H atoms generated by the dissociation of H2 are the main reasons for the significant improvement in the impurity removal rate. The mechanism of Gd purification was analysed based on the above-mentioned experimental results. The as-synthesised Gd2O3 nanoparticles have a uniform spherical structure (average diameter of 32.7 nm), appropriate dispersibility, and high purity. This study provides a new strategy for the integrated purification of metals and preparation of metal/metal-based nanomaterials by DC arc plasma.

Identifying optimal Ru size in NH3 synthesis can improve reaction activity and maximize the utilization of Ru to reduce catalyst cost. However, previous researches are focused on large Ru particle size (≥ 2 nm) while that below 2 nm in NH3 synthesis is unclear. Here we synthesized a series of Rux/BaCeO3 with different Ru sizes (x=1.1–3.0 nm) through size-controlled Ru colloid. With the decrease of Ru size, NH3 synthesis rate over Ru1.1/BaCeO3 increases to 19.4 mmol gcat−1 h−1 at 400°C and 1 MPa, which is 5.7 times that of Ru3.0/BaCeO3 and superior to most of Ru-based catalysts previously reported. It reveals that the reduction of Ru size enhances the generation of Ce3+ and oxygen vacancies in BaCeO3, which can donate electron to Ru centers and promote N2 dissociation. Moreover, the small Ru size enhances hydrogen spillover from Ru to BaCeO3 to alleviate hydrogen poisoning, resulting in efficient NH3 synthesis.

Gas hydrate dissociation may pose serious geohazards. The response of the seafloor to hydrate dissociation is important for geohazards, marine environments and global climate. We studied how hydrate dissociation affects underground temperature and pressure and how dissociation may lead to seafloor deformation. Here, we designed a laboratory model experiment to visualize fluid migration and seafloor deformation during hydrate dissociation at atmospheric pressure. Our experiments show visible gas pipes, migratory gas and gas pockets due to hydrate dissociation and explain the newly discovered discordance between the slide plane and the base of the gas hydrate stability zone. We found that the underlying free gas and gas conduits not only are favorable factors for forming hydrates but also can be promoted by hydrate dissociation. The temperature, pressure, and seafloor deformation are collected during the experiments. Our results show that the hydrate dissociation process is an endothermic reaction. More importantly, hydrate dissociation-induced overpressure exhibits a sudden decrease after slow growth and this inflation–deflation cycle resembles breathing. In our experiments, seafloor deformation are dominated by underground overpressure and lags up to about ten minutes. This deformation pattern could help forecast seafloor subsidence based on deformation observations. Overpressure monitoring is effective and saves time to cope with imminent geohazards. This pattern is important for geologists and engineers to forecast hydrate-related geohazards.

In this study, we investigate the reaction mechanisms of precursor adsorption during the atomic layer deposition (ALD) using density functional theory (DFT) calculations and ideal-gas methods; herein, we considered adsorption of tris(dimethylamino)silane (TDMAS) on a hydroxylated SiO2 surface to be the example for our investigation. When the reaction free energy is calculated, the DFT results obtained at 0 K suggest that the dissociation of a hydrogen atom from TDMAS is favorable upon TDMAS adsorption, which is inconsistent with the experimental results where one dimethylamino group is released. The experimental results can be accurately predicted when enthalpy and entropy changes are considered at elevated temperatures, thereby indicating the significance of finite-temperature effects in free-energy changes for solid-gas reactions. We analyze the changes in enthalpy and entropy and find that dimethylamine is a more favorable gaseous product than H2 owing to its larger translational and rotational entropy.

Single-atom catalysis has aroused enormous attention due to the highly exposed active sites and nearly 100% atomic utilization. However, the relatively low metal atoms loading limits their catalytic activities. Herein, we report N-doped carbon fibers supported Ni single atoms and nanoparticles hybrid (Ni SA /NP-NCF-800) by the combined strategies comprising electrospinning, pyrolysis, and etching. The in-situ formed SiO2 and Ni particles serve as the hard templates to create highly porous architecture throughout the entire fibers, enabling the Ni species to efficiently anchor on carbon matrix to generate a high single atoms loading of 1.83 wt%, as well as provide accessible channels for mass transport and electrolyte diffusion. The unique configuration endows the hybrid with outstanding hydrogen evolution performance along with the low overpotential and robust long-term durability in 1 M KOH. The synchrotron radiation analysis and density functional theory calculations experimentally and theoretically reveal the isolated Ni was coordinated with neighboring four N atoms, which could lead to the re-arranged electron structure of Ni nanoparticles. The synergistic effect of atomically dispersed Ni and nanoparticles leads to the significantly enhanced water adsorption/dissociation abilities and optimized H adsorption free energy in alkaline media, thus paving a new avenue to design single atoms based electrocatalysts.

Interactions between RNA molecules and proteins are critical to many cellular processes and are implicated in various diseases. The RNA-peptide complexes are good model systems to probe the recognition mechanism of RNA by proteins. In this work, we report studies on the binding-unbinding process of a helical peptide from a viral RNA element using nonequilibrium molecular dynamics simulations. We explored the existence of various dissociation pathways with distinct free-energy profiles that reveal metastable states and distinct barriers to peptide dissociation. We also report the free-energy differences for each of the four pathways to be 96.47 ± 12.63, 96.1 ± 10.95, 91.83 ± 9.81, and 92 ± 11.32 kcal/mol. Based on the free-energy analysis, we further propose the preferred pathway and the mechanism of peptide dissociation. The preferred pathway is characterized by the formation of sequential hydrogen-bonding and salt-bridging interactions between several key arginine amino acids and the viral RNA nucleotides. Specifically, we identified one arginine amino acid (R8) of the peptide to play a significant role in the recognition mechanism of the peptide by the viral RNA molecule.

This work aims at revealing the reaction and carbon behavior of SAPO-34/ZSM-5 composite molecular sieve (SZ-TS) in MTO reaction, which is synthesized via in situ two-step crystallization method. Several tests are used to explore the structure–activity relationship of the SZ-TS. The results show that the strength of weak and medium-strong acid is suitable, the particle size of two-phase molecular sieve is decreased, the hierarchical pore structure with abundant mesoporous is formed. By using the SZ-TS in MTO reaction, the methanol conversion and light olefins selectivity are 98% and 92.7%, respectively. These results can be attributed to the interface phase effect produced by etching and dissociation on the skeleton of the nuclear phase SAPO-34. The result of in situ IR and analysis of carbon deactivation indicate that polymethylbenzene is generated as the active intermediate of MTO reaction. SZ-TS with appropriate acid sites and rich mesoporous distribution could alleviate the formation rate of methyl-substituted benzene and polycyclic aromatic hydrocarbons, smaller particle size can avoid the occurrence of secondary reactions of olefins, therefore displaying the excellent resistance to the carbon deposition inactivation, with a catalytic lifetime up to 1380 min.

Fatty acid binding proteins (FABPs) can facilitate the transfer of long-chain fatty acids between intracellular membranes across considerable distances. The transfer process involves fatty acids, their donor membrane and acceptor membrane, and FABPs, implying that potential protein-membrane interactions exist. Despite intensive studies on FABP-membrane interactions, the interaction mode remains elusive, and the protein-membrane association and dissociation rates are inconsistent. In this study, we used nanodiscs (NDs) as mimetic membranes to investigate FABP-membrane interactions. Our NMR experiments showed that human intestinal FABP interacts weakly with both negatively charged and neutral membranes, but it prefers the negatively charged one. Through simultaneous analysis of NMR relaxation in the rotating-frame (R(1ρ)), relaxation dispersion, chemical exchange saturation transfer, and dark-state exchange saturation transfer data, we estimated the affinity of the protein to negatively charged NDs, the dissociation rate, and apparent association rate. We further showed that the protein in the ND-bound state adopts a conformation different from the native structure and the second helix is very likely involved in interactions with NDs. We also found a membrane-induced FABP conformational state that exists only in the presence of NDs. This state is native-like, different from other conformational states in structure, unbound to NDs, and in dynamic equilibrium with the ND-bound state.

Hydrogen activation, storage properties and associated crystal structures of Ti1-xScxMn1.6V0.4 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) alloys are investigated by hydrogenation and XRD. The unit-cells of alloys and hydrides expand with Sc content and hydrogen concentration. Minor addition of Sc significantly improves hydrogen activation and storage properties. The plateau pressure decreases, whereas the sloping factor and relative partial molar enthalpy for hydrogenation increase with Sc content. The activation properties strongly depend on the particle sizes. The bulk samples can easily be activated by implementing a hydrogen-induced cracking mechanism, which avoids removal of protective oxide films and compensates the lack of metallic B-metal in catalysis of hydrogen dissociation. Samples with smaller particle sizes are difficult to activate. The unusual particle size effect is interpreted by activation kinetics, and attributed to the high oxygen binding ability of B-metals and their contribution to the surface oxide films.

Transition metals (TMs) are attractive electrocatalysts for lithium-sulfur (Li-S) batteries due to their strong adsorption of sulfur species based on Lewis acid-base interactions and high intrinsic conductivity. However, S8 molecule undergoes dissociation on their surfaces, resulting in sulfur-poisoned TMs with reduced catalytic sites. We propose here an alloying strategy which changes the S adsorption sites and the corresponding binding energies, enabling intact adsorption of S8 as evidenced by theoretical and experimental results. Such merit renders Co-Te alloy a superior catalyst which effectively expedites the sulfur redox reactions and suppresses the shuttle effect. Consequently, the cathode with Co-Te alloy catalyst delivers an impressive rate capability of 898 mAh g−1 at 2 C together with a low capacity decay of 0.03% per cycle over 1000 cycles. Even the sulfur mass loading is up to 5.4 mg cm−2, a stable capacity of 5.0 mAh cm−2 can be still maintained after 100 cycles. Our work deepens the mechanism understanding of Li-S catalysis and opens a new avenue toward the design of poisoning-resistant electrocatalysts.

Selective hydrogenation of nitroarene to aniline is a key reaction for the manufacture of fine chemicals, pharmaceuticals, and dyes. In this study, N-doped carbon nanotubes (NCNTs) are prepared by the pyrolysis of chitosan-CNTs composite. The outside diameter of CNTs, concentration of chitosan, pyrolysis temperature and heating rate are tuned to improve the catalytic performance. The catalyst of CS/CNTs-800 doped with 0.33% pyrrolic N and 0.30% graphitic N exhibits good activity and high selectivity for the hydrogenation of nitroarenes. The kinetics data reveal that the hydrogenation reaction is zero-order for 4-nitrophenol and first-order dependence to H2 pressure, and H2 dissociation on the active sites is the rate-determining step. On CS/CNTs-800, the nitro groups of 12 different substrates can be selectively reduced with the protection of the other reducible groups. Nonpolar H radicals are found to be formed on CS/CNTs-800 for efficient hydrogenation. In addition, the catalyst showed good stability.

Ketene, a versatile reagent in production of fine and specialty chemicals, is produced from acetic acid. We investigate the synthesis of ketene from acetic acid over the (3,0;1,1) surface of Cu2O(1 0 0) through analysis of the adsorption and desorption characteristics of formic and acetic acids. The results allow us to establish a reaction mechanism for ketene formation. Observations from x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy, and temperature programmed desorption (TPD), supported by a comparison with formic acid results, suggest that acetic acid reacts with Cu2O through deprotonation to form acetate species coordinated to copper sites and hydroxylation of nearby surface oxygen sites. For formic acid the decomposition of adsorbed formate species results in desorption of CO2 and CO while, for acetic acid, high yields of ketene are observed at temperature >500 K. Modeling by density functional theory (DFT) confirms the strong interaction of acetic acid with the (3,0;1,1) surface and the spontaneous dissociation into adsorbed acetate and hydrogen atom species, the latter forming an OH-group. In an identified reaction intermediate ketene binds via all C and O atoms to Cu surface sites, in agreement with interpretations from XPS. In the vicinity of the adsorbate the surface experiences a local reorganization into a c(2 × 2) reconstruction. The total computed energy barrier for ketene formation is 1.81 eV in good agreement with the 1.74 eV obtained from TPD analysis. Our experimental observations and mechanistic DFT studies suggests that Cu2O can operate as an efficient catalyst for the green generation of ketene from acetic acid., Swedish Research Council (VR); VR Starting Grant; Knut och Alice Wallenbergs stiftelse; STINT Joint China-Sweden Mobility Program; Ragnar Holm Foundation; Trygger’s Foundation; Chalmers Areas of Advance-Materials Science

Photocatalytic water splitting for hydrogen energy is one of the most promising ways to solve the energy crises. The mechanism is unclear on the sequence of proton coupled electron transfer (PCET) in photocatalytic water dissociation catalyzed by organic material. Here, the water splitting catalyzed by zinc porphyrin with boron dipyrrin (ZnPP-BDP) is systematically investigated by density functional theory (DFT) calculations. The H2O/ZnPP in valence state based on the electron transfer pulls the trigger on the water splitting process. For the oxygen evolution reaction (OER) step on ZnPP, the processes for the two H ions dissociate from water are exothermic with the −1.06 and −0.95 eV energies respectively, and the O/ZnPP system is formed. The second H2O molecule on O/ZnPP system can provide the extra oxygen atom to produce the free O2 with 1.22 eV energy barrier. For the hydrogen evolution reaction (HER) step on BDP, the H ions dissociated from OER process can be captured by BDP to form free H2 with 2.24 eV/molecule energy released. In this attractive clean cyclic process, the ZnPP-BDP can continuously catalyze the H2O dissociated into free H2 and O2 by the shifting potential barrier. Besides, the proton coupled electron sequent transfer possess an essential role in photocatalytic water dissociation. It is very instructive to design sustainable photodecomposition catalysts for both OER and HER, and to design extraordinary biomimetic photosynthesizers for clean energy.

Ab initio calculations have been carried out to investigate the adsorption, dissociation, and diffusion of atomic and molecular hydrogen on the Fe-doped ZrCo (110) surface. It is found that the adsorption of H2 on doped surface seems thermodynamically more stable with more negative adsorption energy than that on the pure surface, and the dissociation energy of H2 on doped surface is much bigger therefore. However, compared with the pure system, there are fewer adsorption sites for spontaneous dissociation. After dissociation, the higher hydrogen adsorption strength sites would promote the H atom diffusion towards them where they can permeate into the bulk further. Furthermore, the ZrCo (110) surface possesses much higher hydrogen permeability and lower hydrogen diffusivity than its corresponding ZrCo bulk. Moreover, further comparison of the present results to analogous calculations for pure surface reveals that the Fe dopant facilitates the H2 molecule dissociation. Unfortunately, this does not improve the hydrogen storage performance of ZrCo alloy due to the H atom diffusion on the surface and into bulk are prevented with higher reaction energetic barriers by doping Fe. Consequently, ZrCo (110) surface modified with Fe atoms should not be preferred as a result of its terrible hydrogen permeability. A clear and deep comprehending of the inhibiting effect of Fe dopant on the hydrogen storage of ZrCo materials from the perspective of the surface adsorption of hydrogen are obtained from the present results.

The cathode of a protonic ceramic fuel cell must be able to facilitate ion and electron transfer, while simultaneously possessing a high catalytic activity for steam generation and the dissociation of gas-phase molecules. In this study, the performance of a cathode for protonic ceramic fuel cells is optimized by employing a triple-component composite cathode design, which integrates proton conductors, mixed electronic–ionic conductors, and a catalytic layer. Additionally, two other composite cathodes are fabricated for comparison. Owing to its higher electrical conductivity but lower catalytic activity, the composite cathode with protonic ceramic and (Ba0.95La0.05) (Fe0.8Zn0.2)O3-δ (BLFZ) exhibits lower ohmic resistance but poor catalytic activity compared to the composite cathode with protonic ceramic and Ba(Co0.4Fe0.4Zr0.1Y0.1)O3-δ (BCFZY). The triple-component cathode is fabricated by infiltrating BCFZY into a composite cathode composed of BLFZ and protonic ceramic, and both the ohmic and non-ohmic resistances of the cathode are optimized in CH4 and H2 fuels. In particular, the performance of CH4 fuel is significantly improved by adopting a triple-component cathode. These results suggest a possible contribution of the oxygen reduction reaction at the cathode to the reformation of CH4 at the anode.

Hydrogen is an energy carrier found from renewable sources such as biomass, geothermal, solar, or wind. Water splitting and dehydrogenation of glycerol is a sustainable process of H2 production from renewables because water is abundant, and the glycerol is formed from the biomass-derived compounds. However, finding a suitable and best catalyst for these processes is challenging. Thus, this paper proposed a theoretical study to find the mechanism of the dissociation of water and dehydrogenation of glycerol using Au metal and PdAu alloy catalysts using the density functional theory (DFT) method. Four PdAu alloys have been constructed with different atomic compositions ranging from 1 to 3 of Pd metal to Au metal. The result showed strong adsorption on the Pd1Au3 catalyst surface, and the water splitting is best on the Pd3Au1 catalyst surface. Simultaneously, the glycerol adsorption on catalyst surfaces is tested before proceeding for the complete dehydrogenation mechanism of glycerol. Strong adsorption was found at the Pd1Au3 catalyst compared to other catalyst surfaces on the glycerol adsorption. The dehydrogenation mechanism was found toward a downhill reaction and removed eight hydrogens from the glycerol compared to Au metal, referring to easy dehydrogenation of glycerol using the alloy PdAu. The final species that adsorbed on the Pd1Au3 surface is the carbon monoxide will be turned later into carbon dioxide.

Background Chitosan (CS) is the most abundant cationic biopolymer on earth. However, the ionic conductivity performance of CS polymer electrolyte is relatively poor, restricting the application in energy storage devices. Methods Subject to carboxylation at pH of 6. 8, and 10, CS turns into CCS6, CCS8, and CCS10 respectively with the DC of 100.9%, 20.0%, and 17.8%, respectively. Significant findings From the Arrhenius plot, the activation energy of CS, CCS6, CCS8, and CCS10 electrolytes is estimated as 11.7, 2.5, 2.6, and 2.6 kJ/mol respectively. As for supercapacitor performance, CCS6 remains 57.2% capacitance but the others remain 0% with decreasing temperature from 25 °C to -7 °C. At -7 °C, only CCS6 supercapacitor shows relaxation peak in loss tangent versus frequency plot around 2 × 105 Hz according to dissociated ion pairs, being attributable to the existence of bound water. Three water states are examined by Differential Scanning Calorimetry (DSC) and Raman, verifying that CCS6 possesses high bound water proportion of 24.7%. With the highest DC, CCS6 possesses the almost equivalent amine and carboxyl groups in one glucosamine unit to play an important role to enhance dissociation, defer the breakpoints of ionic conductivity, and remain certain proportion of bound water for promising capacity at low temperature.

Cesium lead halide perovskite nanocrystals (PNCs) are highly attractive for optoelectronic applications due to their tunable bandgap, large absorption cross section and efficient photoluminescence. However, the dynamic ligand binding and ionic lattice make PNCs extremely sensitive to polar solvents, which greatly hinders the applications of PNCs. In this work, we first synthesize ethanol-dispersed PNCs with the assistance of water using glycyrrhizic acid (GA) as the sole capping ligand. The prepared PNCs with a mean size of 14.5 nm exhibit a narrow and symmetric emission band (full width at half maximum: 18 nm) and photoluminescence (PL) quantum yield (QY) of ~38.1%. Different with the common sense, the addition of water promotes the formation of GA-passivated PNCs due to the accelerated reaction rate of precursors and the H+ dissociation of GA at presence of Lewis base water. Furthermore, the ethanol-dispersed PNCs can be further transformed into emissive ethanol gels with improved stability. Our findings provide a novel strategy to achieve stable colloidal PNCs in polar solvents.

Addition of rare earth oxide, especially lanthanide oxide, was regarded as a promising strategy to improve the carbon resistance for Nickel-based catalysts in dry reforming of methane (DRM). In this work, Nickel-based catalysts containing lanthanide oxides (NiLa/SiO2, NiCe/SiO2, NiSm/SiO2, and NiGd/SiO2) were prepared and employed to catalyze DRM. Lanthanide oxide affected the formation of Ni nanoparticles in different size. In NiLa/SiO2 and NiCe/SiO2, Ni nanoparticles maintained relatively small size (4 nm), while in NiSm/SiO2 and NiGd/SiO2, nickel particles were in large size (8 nm). NiLa/SiO2 and NiCe/SiO2 exhibited better stability than the other two catalysts, with CH4 conversion decreasing from 64.6 to 57.6% and 61.6 to 60.3%, respectively in 10 h on stream. The kinetic study confirmed that adding lanthanide oxide significantly affected the activation energy of CH4 dissociation and CO2 dissociation. Compared to monometallic Ni/SiO2, the presence of Sm and Gd suppressed CO2 dissociation, and introduction of Ce and La effectively promoted CO2 dissociation. These characters contributed to the higher carbon resistance and good stability for NiLa/SiO2 and NiCe/SiO2 catalysts in DRM reaction.