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Ammonia (NH3) is a basic chemical feedstock for the production of fertilizers and pharmaceuticals, and it emerges as a new hydrogen energy carrier for renewable energy sources such as solar and wind power. A photoelectrochemical nitrogen reduction reaction (PEC NRR) under mild operating conditions represents a potentially green and convenient approach for the synthesis of NH3. However, a generally applicable PEC NRR featuring a high NH3 yield and a satisfactory conversion efficiency remains elusive. Herein, we report on a simple and effective electrochemistry-assisted strategy to enhance the PEC fixation of N2 to NH3. Using this strategy, we harness a steel-based cathode-assisted Au/SiO2/Si photocathode to seamlessly combine two critical reaction steps-N2 activation and hydrogenation-to realize an NH3 yield rate of 22.0 μg·cm-2·h-1 and a faradic efficiency of 23.7% at-0.2 V versus a reversible hydrogen electrode under one sun illumination. We also provide an accessible reaction setup to avoid the disturbance of a contamination by air, human breath, and N2 stream, leading to a reliable production of NH3 by the PEC NRR. An operando characterization and a theoretical calculation uncover the active sites and reaction mechanism of the whole system for an electrochemistry-assisted PEC NRR. This work demonstrates the capability of an electrochemistry-assisted excitation in PEC NRR, and it introduces a new design concept for addressing pertinent challenges in photoelectrochemical and other chemical fields.

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Integrating carbon nitride with graphene into a lateral heterojunction would avoid energy loss within the interlaminar space region on conventional composites. To date, its synthesis process is limited to the bottom-up method which lacks the targeting and homogeneity. Herein, we proposed a hydrogen-initiated chemical epitaxial growth strategy at a relatively low temperature for the fabrication of graphene/carbon nitride in-plane heterostructure. Theoretical and experimental analysis proved that methane via in situ generation from the hydrogenated decomposition of carbon nitride triggered the graphene growth along the active sites at the edges of confined spaces. With the enhanced electrical field from the deposited graphene (0.5%), the performances on selective photo-oxidation and photocatalytic water splitting were promoted by 5.5 and 3.7 times, respectively. Meanwhile, a 7720 μmol/h/g(graphene) hydrogen evolution rate was acquired without any cocatalysts. This study provides an top-down strategy to synthesize in-plane catalyst for the utilization of solar energy.

Single-atom catalysts (SACs) have attracted much attentions due to the advantages of high catalysis efficiency and selectivity. However, the controllable and efficient synthesis of SACs remains a significant challenge. Herein, we report a controlled one-pot synthesis of nickel single atoms embedded on nitrogen-doped carbon nanotubes (NiSA−N−CNT) and nitrogen-doped graphene (NiSA−N−G). The formation of NiSA−N−CNT is due to the solid-to-solid rolling up mechanism during the high temperature pyrolysis at 800 °C from the stacked and layered Ni-doped g-CN, g-CN−Ni structure to a tubular CNT structure. Addition of citric acid introduces an amorphous carbon source on the layered g-CN−Ni and after annealing at the same temperature of 800 °C, instead of formation of NiSA−N−CNT, Ni single atoms embedded in planar graphene type supports, NiSA−N−G were obtained. The density functional theory (DFT) calculation indicates the introduction of amorphous carbon source substantially reduces the structure fluctuation or curvature of layered g-CN-Ni intermediate products, thus interrupting the solid-to-solid rolling process and leading to the formation of planar graphene type supports for Ni single atoms. The as-synthesized NiSA−N−G with Ni atomic loading of ∼6 wt% catalysts shows a better activity and stability for the CO reduction reaction (CORR) than NiSA−N−CNT with Ni atomic loading of ∼15 wt% due to the open and exposed Ni single atom active sites in NiSA−N−G. This study demonstrates for the first time the feasibility in the control of the microstructure of carbon supports in the synthesis of SACs.

Tar formation is practically unavoidable during gasification. Catalytic tar forming is one of the most promising techniques for producing high-quality syngas at a commercial scale. Biochar has great potential to be used as a catalyst for the removal of tar from the syngas produced from the pyrolysis/gasification of biomass. The structure of biochar is a critical factor affecting its catalytic performance. This study investigates the role of O-containing functional groups in biochar during steam reforming of tar using biochar as a catalyst. Mallee wood biochar (106–250 μm) was activated in H2O for different times (0–50 min) and then used as a catalyst for the steam reforming of tar at 800 °C. The chemical structural features of biochars were characterized with Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that H2O activation increased the concentration of O-containing functional groups, mainly the aromatic C O structures in biochar, which enhanced the catalytic destruction of tar. During the catalytic reforming of tar, the content of aromatic C O groups decreased while the catalyst activity decreased. It is believed that the aromatic C O functional groups in biochar play a vital role in the steam reforming of tar.

This article presents a comprehensive study on surface chemical bonding states, morphological features, mechanical properties, finite element modeling, and water contact angle measurements of wet chemical based dip-coated CoZn-oxide thin film coatings. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Nanoindentation, finite element method (FEM) modeling, and drop shape analysis techniques were used to carry out the detailed measurements. AFM studies showed that the surface roughness values of all the coatings sturdily increased with the increase in sol concentrations. The gradual increase in sol concentrations and annealing temperature also had a remarkable influence over the Co , and Zn-contents of these coatings given by XPS analysis. The deconvolution of Co 2p3/2 photoelectron lines revealed the formation of Co(OH)2, CoO, Co2O3, and Co3O4 phases from the coatings surface while low intensity satellite peaks developed due to a partial spinel lattice structure of Co-ions. The occurrence of Co3O4, CoO, and ZnO phases were also confirmed from the deconvolution of O 1s photoelectron lines. The elastic modulus, E, of CoZn-oxide thin film coating, varied within the range of 43.7–69.2 GPa was comparable with that in CoCuO thin film coatings. The maximum stress level induced was estimated to be in the range of 4.0–6.5 GPa. However, as the thickness of the coatings is increased, the maximum stress level slightly decreased. The coatings were moderately hydrophobic.

The temperature dependence of phase composition and lattice parameters, for TiAlxN thin film coating, are experimentally investigated by in-situ synchrotron radiation X-ray diffraction (SR-XRD), at temperatures between 25 °C and 700 °C. Mechanical properties, such as: Young's modulus (E), hardness (H) and plastic deformation index (PDI) – were experimentally determined by nanoindentation, at 25 °C. Crystalline structural analysis, of SR-XRD results, indicates the major phases are TiN and AlN; with Ti2O and TiO2 phases also present above 600 °C. The lattice constants increased with an increase in temperature. Atomic and phase compositions, at 25 °C, were also verified by X-ray photoelectron spectroscopy (XPS). Field emission scanning electron microscopy (FESEM) images display an increase in surface roughness and reduction in grain size, with increasing Aluminium percentage (Al%). Nanoindentation analysis showed a maximum hardness of 25.1 ± 1.5 GPa (sample containing 12% Al), which was subsequently reduced upon addition of more Aluminium. Finite element modelling (FEM), including von Mises stress distribution, indicates lower mechanical integrity, for samples with high Al% content.

Microbial contribution to gold biogeochemical cycling has been proposed. However, studies have focused primarily on the influence of prokaryotes on gold reduction and precipitation through a detoxification-oriented mechanism. Here we show, fungi, a major driver of mineral bioweathering, can initiate gold oxidation under Earth surface conditions, which is of significance for dissolved gold species formation and distribution. Presence of the gold-oxidizing fungus TA_pink1, an isolate of Fusarium oxysporum, suggests fungi have the potential to substantially impact gold biogeochemical cycling. Our data further reveal that indigenous fungal diversity positively correlates with in situ gold concentrations. Hypocreales, the order of the gold-oxidizing fungus, show the highest centrality in the fungal microbiome of the auriferous environment. Therefore, we argue that the redox interaction between fungi and gold is critical and should be considered in gold biogeochemical cycling., The role of fungi in the biogeochemical cycling of gold remains unclear. Here the authors show that fungi can initiate gold oxidation under supergene conditions, thereby impacting gold mobilisation and secondary deposit formation in terrestrial environments.

Supported single atom catalysts (SACs), emerging as a new class of catalytic materials, have been attracting increasing interests. Here we developed a Ni SAC on microwave exfoliated graphene oxide (Ni-N-MEGO) to achieve single atom loading of ∼6.9 wt%, significantly higher than previously reported SACs. The atomically dispersed Ni atoms, stabilized by coordination with nitrogen, were found to be predominantly anchored along the edges of nanopores (

Ce/Ti mixed metal oxide thin films have well known optoelectrical properties amongst several other physio-chemical properties. Changes in the structural and mechanical properties of magnetron sputtered Ce/Ti oxide thin films on Si (100) wafers with different Ce:Ti ratios are investigated experimentally and by modelling. X-ray Photoemission Spectroscopy (XPS) and X-ray diffraction (XRD) confirm the primary phases as trigonal Ce2O3 and rutile form of TiO2 with SiO2 present in all prepared materials. FESEM imaging delivers information based on the variation of grain size, the mixed Ce/Ti oxides providing much smaller grain sizes in the thin film/substrate composite. Nanoindentation analysis concludes that the pure cerium oxide film has the highest hardness value (20.1 GPa), while the addition of excess titanium oxide decreases the hardness of the film coatings. High temperature in-situ XRD (up to 1000 degrees C) results indicate high thermal phase stability for all materials studied. The film with Ce:Ti = 68%:32% has a new additional minor oxide phase above 800 degrees C. Contact angle experiments suggest that the chemical composition of the surface is insignificant affecting the water contact angle. Results show a narrow band of 87.7-95.7 degrees contact angle. The finite element modelling (FEM) modelling of Ce/Ti thin film coatings based on Si(100); Si(110); silica and steel substrates shows a variation in stress concentration.

Hybrid nanomaterials offer increased flexibility to achieve heterostructures with controlled functionalities and predictable linkages owing to their synergistic interactions. Here, we have developed a synthetic strategy that produced hexagonal-shaped nanoplatelets (NPLs) of gold–pyrrhotite (Au–Fe7S8) with Au embedded inside them by means of a seeded growth method. Using thiol-capped Au nanoparticles (NPs) as a seed, heterogeneous nucleation of the iron precursor was facilitated, leading to the formation of Au–Fe7S8 NPLs. The injection temperature and surface ligand of the seed (Au) were two critical factors that determined the homogeneity and final morphology of the Au–Fe7S8 NPLs. This strategy was further expanded using Ag NPs as the seed to construct heterodimers, producing Ag2S–Fe7S8 heterostructures.

Electrically insulating objects gain a net electrical charge when brought in and out of contact. This phenomenon-triboelectricity-involves the flow of charged species, but conclusively establishing their nature has proven extremely difficult. Here, we demonstrate an almost linear relationship between a plastic sample's net negative charge and the amount of solution metal ions discharged to metallic particles with a coefficient of proportionality linked to its electron affinity (stability of anionic fragments). The maximum magnitude of reductive redox work is also material dependent: metallic particles grow to a larger extent over charged dielectrics that yield stable cationic fragments (smaller ionization energy). Importantly, the extent to which the sample can act as electron source greatly exceeds the net charging measured in a Faraday pail/electrometer set up, which brings direct evidence of triboeletricity being a mosaic of positive and negative charges rather than a homogeneous ensemble and defines for the first time their quantitative scope in electrochemistry.

g-C3N4 crystalline/amorphous lateral-like homostructures were prepared using crystalline g-C3N4 nanosheets as seeds via sequential edge-epitaxy growth. The homojunction effectively separates photogenerated carriers, resulting in high photo- and electro-catalytic activities.

Metal oxides have been extensively applied as heterogeneous catalysts in various chemical processes, including conventional heterogeneous catalysis, photocatalysis, and membrane catalysis. The catalytic performance of an oxide heterogeneous catalyst can be affected by its lattice structure, electronic structure, surface properties, bulk defects, and metal–oxygen bond strength. As a catalytic membrane, the catalytic performance of an oxide may also strongly depend on its oxygen-ion diffusion properties. Cation doping has been extensively adopted to tailor, both physically and chemically, the properties of oxide materials, such as lattice structure, electronic structure, lattice defects and diffusion behavior, so as to alter their catalytic performance for various redox reactions. Very recently, anion doping into the oxygen site has emerged as a new strategy for tuning the chemical and physical properties of metal oxides, and thus for regulating their catalytic behavior. Here, a timely review of recent progress in the development of advanced oxide catalysts based on oxygen-site anion doping is provided. Emphasis is given to the effect of doping anions into the metal oxide lattice on the physical and chemical properties, and consequently the performance in various catalytic applications, including the oxidative dehydrogenation of ethane (ODE), oxidative coupling of methane (OCM), photocatalytic reduction of dyes, and ceramic membrane-based oxygen separation. The aim of the current review is to offer some insightful perspectives to guide the development of functional oxide materials based on the anion site doping strategy toward application in heterogeneous catalysis. The knowledge gained here may also be useful for other application fields, such as electrochemical energy storage devices and sensors.

The development of oxygen evolution reaction (OER) electrocatalysts remains a major challenge that requires significant advances in both mechanistic understanding and material design. Recent studies show that oxygen from the perovskite oxide lattice could participate in the OER via a lattice oxygen-mediated mechanism, providing possibilities for the development of alternative electrocatalysts that could overcome the scaling relations-induced limitations found in conventional catalysts utilizing the adsorbate evolution mechanism. Here we distinguish the extent to which the participation of lattice oxygen can contribute to the OER through the rational design of a model system of silicon-incorporated strontium cobaltite perovskite electrocatalysts with similar surface transition metal properties yet different oxygen diffusion rates. The as-derived silicon-incorporated perovskite exhibits a 12.8-fold increase in oxygen diffusivity, which matches well with the 10-fold improvement of intrinsic OER activity, suggesting that the observed activity increase is dominantly a result of the enhanced lattice oxygen participation., While water splitting provides a renewable means to store energy, the sluggish O2 evolution half-reaction limits applications. Here, authors examine a silicon-incorporated strontium cobaltite perovskite and correlate lattice oxygen participation in O2 evolution to the oxygen ion diffusivity.

Gold nanorods are one of the most widely explored inorganic materials in nanomedicine for diagnostics, therapeutics and sensing1. It has been shown that gold nanorods are not cytotoxic and localize within cytoplasmic vesicles following endocytosis, with no nuclear localization2,3, but other studies have reported alterations in gene expression profiles in cells following exposure to gold nanorods, via unknown mechanisms4. In this work we describe a pathway that can contribute to this phenomenon. By mapping the intracellular chemical speciation process of gold nanorods, we show that the commonly used Au–thiol conjugation, which is important for maintaining the noble (inert) properties of gold nanostructures, is altered following endocytosis, resulting in the formation of Au(i)–thiolates that localize in the nucleus5. Furthermore, we show that nuclear localization of the gold species perturbs the dynamic microenvironment within the nucleus and triggers alteration of gene expression in human cells. We demonstrate this using quantitative visualization of ubiquitous DNA G-quadruplex structures, which are sensitive to ionic imbalances, as an indicator of the formation of structural alterations in genomic DNA. The release of nuclear-localizing gold species from intracellular gold nanorods may alter gene expression on interaction with the genomic DNA.

The influence of the reaction gas composition during the DC magnetron sputtering process on the structural, chemical and optical properties of Ce-oxide thin films was investigated. X-ray diffraction (XRD) studies confirmed that all thin films exhibited a polycrystalline character with cubic fluorite structure for cerium dioxide. X-ray photoelectron spectroscopy (XPS) analyses revealed that cerium is present in two oxidation states, namely as CeO2 and Ce2O3, at the surface of the films prepared at argon-oxygen flow ratios between 0–7%, whereas the films are completely oxidized into CeO2 as the aforementioned ratio increases beyond 14%. Various optical parameters for the thin films (including an optical band gap in the range of 2.25 – 3.1 eV) were derived from the UV-Vis reflectance. A significant change in the band gap was observed as the oxygen pressure was raised from 7% to 14% and this finding is consistent with the high-resolution XPS analysis of Ce 3d that reports a mixture of Ce2O3 and CeO2 in the films. Density functional theory (DFT+U) implemented in the Cambridge Serial Total Energy Package (CASTEP) was carried out to simulate the optical constants of CeO2 clusters at ground state. The computed electronic density of states (DOSs) of the optimized unit cell of CeO2 yields a band gap that agrees well with the experimentally measured optical band gap. The simulated and measured absorption coefficient (α) exhibited a similar trend and, to some extent, have similar values in the wavelength range from 100 to 2500 nm. The combined results of this study demonstrate good correlation between the theoretical and experimental findings.

This study investigated the susceptibility to pitting corrosion of 316L in CO2 and N2 environments at temperatures from 30 to 80°C in 3 wt-% NaCl at pH 4. Results from cyclic polarisation technique...

Nanofibrous NiAl2O4/Al2O3 ceramic was prepared by electrospinning and subsequent calcination at 1000 °C. Under reducing atmosphere, Ni nanoparticles in situ grew from and were rooted in nanofibrous support. The anchored Ni-NiOx nanocatalysts showed the strong interaction with Al2O3-NiAl2O4 supports owing to the incompletion of NiAl2O4 and NiO reduction and therefore high resistances to aggregation and carbon formation. The nanofibrous catalysts have the advantages of both metal gauze catalysts (fast mass transfer) and supported catalysts (nanosized catalysts). Compared with conventional supported Ni-based catalysts, the nanofibours catalysts produced the highest syngas production during methane partial oxidation at the highest recorded gas hourly space velocity of 8 × 106 L∙Kg−1 h−1. The catalytic reaction was operated for 10 h without noticeable performance degradation and the fibrous structure of the nanocatalysts was retained.

Bismuth oxide is as an active promoter in enhancing the ionic conductivity and electrocatalytic activity of manganite oxygen electrodes of solid oxide cells, but there are very limited reports on the formation and evolution of electrode/electrolyte interface of bismuth oxide-manganite composite electrode under the influence of electrochemical polarization. Herein, we report the effect of electrochemical polarization and direction of polarization current on the electrocatalytic performance and electrode/electrolyte interface of a (La0·8Sr0.2)0.95Mn0·95Pt0·05O3+δ-Er0.4Bi1·6O3 (LSMPt-ESB) composite oxygen electrode assembled on zirconia electrolyte. The cell with the LSMPt-ESB electrode produces outstanding performance for power generation and steam splitting, and it is stable without noticeable degradation during operation at 600 °C for 350 h in the fuel cell mode. The cathodic polarization induces in operando formation of electrode/electrolyte interface with observation of an Er-deficient LSMPt-ESB dense layer and Er-rich (Er,Bi,Mn)Ox particles on the zirconia electrolyte surface. This is different to the case of dwell under open circuit and in particular under anodic polarization conditions. The present study gains insights into the development of high performance, reliable bismuth oxide-manganite composite oxygen electrode for reduced temperature solid oxide cells.

Chromium nitride (CrN) coatings were deposited by magnetron sputtering onto Si(100) substrates. The coatings were then annealed at different temperatures (500–800 °C in steps of 100 °C) in air for 1 h. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, nanoindentation tests and finite element modeling (FEM) were conducted in order to investigate their structural, morphological, optical and mechanical properties. XRD patterns show that the crystallinity of the CrN phase increases with the rise in annealing temperatures together with its preferred orientations along (111) and (200) diffraction planes. The lattice constants were slightly reduced from 4.19 to 4.11 nm at 800 °C. The lattice micorstrains and residual stresses were also reduced as the annealing temperatures rose as a result of reduced defects, dislocations and vacancies. Smooth grain-like surfaces with grain sizes ranging between ∼50 and 250 nm were confirmed by FESEM micrographs. XPS studies indicated the existence of Cr and N on the coating systems. Optical studies showed that with the rise in annealing temperature of up to 700 °C, the solar absorptance of CrN coatings is increased from 61% to 89% and slightly decreased at 800 °C, while the optical band-gap energy dropped from 2.62 to 1.38 eV and slightly increased to 1.48 eV at 800 °C. A gradual increase of dielectric constants of CrN films were realized with the subsequent annealing progression. Nanoindentation results indicated that as the annealing progresses, the hardness and elastic modulus values are lowered.

This contribution investigates the effect of the addition of the Hubbard U parameter on the electronic structural and mechanical properties of cubic (C-type) lanthanide sesquioxides (Ln2O3). Calculated Bader's charges confirm the ionic character of Ln–O bonds in the C-type Ln2O3. Estimated structural parameters (i.e., lattice constants) coincide with analogous experimental values. The calculated band gaps energies at the Ueff of 5 eV for these compounds exhibit a non-metallic character and Ueff of 6.5 eV reproduces the analogous experimental band gap of cerium sesquioxide Ce2O3. We have thoroughly investigated the effect of the O/Ce ratios and the effect of hafnium (Hf) and zirconium (Zr) dopants on the reduction energies of CeOx configurations. Our analysis for the reduction energy of CeO2, over a wide range of temperatures displays that, shuffling between the two +4 and +3 oxidation states of Ce exhibit a temperature-independent behaviour. Higher O/Ce ratios necessitate lower reduction energies. Our results on Ce–Hf–Zr–O alloys are in reasonable agreements with analogous fitted values pertinent to lowering reduction energies and shrinkage in lattice parameters when contrasted with pure CeO2. Structural analysis reveals that Hf and Zr atoms in the solid solution are shifted towards the nearest vacancies upon reduction. It is hoped that values provided herein to shed an atomic-base insight into the reduction/oxidation thermodynamics of increasingly deployed catalysts for environmental applications.

Metal-oxide nanoclusters (NCs) such as FeOx, CoOx, and NiOx are incorporated into iron phthalocyanine (FePc) supported on graphene, MOx/FePc, via a facile self-assembly method. MOx/FePc electrocatalysts show high activity, selectivity and stability for the electrochemical CO2 reduction reaction (CO2RR) as compared with the corresponding metal phthalocyanines, i.e., FePc, CoPc and NiPc, under identical test conditions. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy reveals that MOx/FePc undergoes a metal ion replacement of the iron center of Pc, forming electrochemically substituted metal Pc, e-MPc where M = Co and Ni, co-existing with the replaced FeOx nanoparticles (NPs) in the vicinity of the e-MPc. The results indicate that the e-MPc with in situ dispersed FeOx NPs, FeOx/e-CoPc and FeOx/e-NiPc exhibits excellent activity, high selectivity and stability for the CO2RR.

Rechargeable Zn–air battery is limited by the sluggish kinetics and poor durability of the oxygen catalysts. In this Research Article, a new bifunctional oxygen catalyst has been developed through embedding the ultrafine NiFeO nanoparticles (NPs) in a porous amorphous MnOx layer, in which the NiFeO-core contributes to the high activity for the oxygen evolution reaction (OER) and the amorphous MnOx–shell functions as active phase for the oxygen reduction reaction (ORR), promoted by the synergistic effect between the NiFeO core and MnOx shell. The synergistic effect is related to the electron drawing of NiFeO core from MnOx shell, which decreases the affinity and adsorption energy of oxygen on MnOx shell and significantly increases the kinetics of ORR. The electrocatalytic activity and durability of NiFeO@MnOx depends strongly on the NiFeO:MnOx ratio. NiFeO@MnOx with NiFeO:MnOx weight ratio of 1:0.8 shows the best performance for reversible ORR and OER, with a potential gap (ΔE) of 0.792 V to achieve a curr...

Metal oxide–carbon composites with core–shell, yolk–shell and hollow structures have attracted enormous interest because of their applications in lithium-ion batteries. However, the relationship between structure and battery performance is still unclear. Herein, we report the designed synthesis of unique core–shell, yolk–shell and hollow Fe3O4@carbon microboxes through a one-step Stober coating method, followed by a carbonization process. Different calcination temperatures were investigated to manipulate the various structures, and the impact of layer thickness on the battery performance was also assessed. Our results showed that the core–shell structured Fe3O4@carbon microboxes with nitrogen-doped carbon shells having a thickness of 15 nm exhibited an excellent performance in lithium-ion batteries with a high reversible capacity of 857 mA h g−1 that could be retained after 100 cycles at a current density of 0.1 A g−1.

Phosphate poisoning of Pt electrocatalysts is one of the major barriers that constrains the performance of phosphoric acid-doped polybenzimidazole (PA/PBI) membrane fuel cells. Herein, we developed new atomically dispersed bimetallic FeCu coordinated with nitrogen-doped carbon nanotubes (FeCu/N-CNTs) as Pt-free oxygen reduction reaction (ORR) electrocatalysts. The cell with FeCu/N-CNTs cathodes delivers a peak power density of 302 mWcm−2 at 230℃, similar to that using Pt/C electrocatalysts (1 mgPt cm−2) but with a much better stability. In contrast to phosphate poisoning of Pt/C, FeCu/N-CNTs show PA enhanced activities. DFT calcualtions indicate that phosphate promotion effect results from the stronger binding of phosphate on Cu sites, which decreases the activation energy barrier for the cleavage of the O2 double bond and provides local protons to facilitate the proton-coupled electron transfer ORR. The results also show that FeCu/N-CNTs have a much better activity for ORR as comapre to Fe single atom catalysts coordinated with nitrogen-doped carbon nanotubes, Fe/N-CNTs. This study demonstrates the promising potential of bimetallic FeCu/N-CNTs as true Pt-free, highly active and durable cathodes for PA/PBI based high temperature polymer electrolyte fuel cells.

Carbon materials are promising alternatives to noble metal catalysts for oxygen reduction reactions (ORR) in energy conversion devices. Here we report hierarchically porous carbon microspheres with a trace amount of encapsulated cobalt as highly active and stable electrocatalysts for the ORR under wide pH values ranged from high alkaline to high acidic conditions. We use renewable natural date pulp as the carbon precursor and a facile hydrothermal carbonization method with in situ formed recyclable cobalt as a template for the synthesis. These catalysts yield competitive catalytic activity (a small Tafel slope of 53 mV dec-1) as well as superb durability and methanol tolerance compared to the benchmark Pt/C catalyst in alkaline electrolyte. Even under harsh acidic conditions, the catalysts deliver a satisfactory catalytic performance and good stability, indicating their extensive applicability. This performance is mainly attributed to the rich surface defects and the hierarchically porous structure that provide abundant active sites for the ORR. In situ formed cobalt nanoparticles are critical to the creation of the abundant mesopores, high specific surface area, and catalytically active defect sites over the carbon material. The encapsulated cobalt residual further enhances the ORR activity of the catalysts, while having a negligible effect on the cost due to its trace level (0.2 at.%).

Oxygen anion intercalation-type supercapacitors are promising charge storage devices. In this study, by taking advantage of the capability of selective exsolution of elements from perovskite lattice, a nanoparticles-modified perovskite composite is developed as new perovskite-based electrode for supercapacitor with further improved performance that allow the energy storage via two different mechanisms, i.e., Faradaic surface redox pseudocapacitance and oxygen anion-intercalation pseudocapacitance. The derived supercapacitor shows high power density and energy density, and no surface activation process, and stable performance. Specifically, perovskite oxides with the nominal composition of Sr2CoMo1-xNixO6-δ are designed and the strategy of controlled in-situ exsolution and re-oxidation of B-sites Ni and Co element to create Co3O4 and NiO nanoparticles on the perovskite surface and extra oxygen vacancies in perovskite bulk is applied. The Co3O4 and NiO nanoparticles on surface of electrode are found to effectively improve the surface redox pseudocapacitance, while the creation of additional oxygen vacancies enhances the oxygen anion intercalation pseudocapacitance. Consequently, the electrode displays excellent charge storage capability with a stable capacity as high as ~930 F g−1 and superior rate performance. As a universal strategy, it may also be applicable for the design and synthesis of alternative high-performance electrodes with mixed energy storage mechanisms.

Summary Rechargeable Zn-ion batteries working with manganese oxide cathodes and mild aqueous electrolytes suffer from notorious cathode dissolution during galvanostatic cycling. Herein, for the first time we demonstrate the dynamic self-recovery chemistry of manganese compound during charge/discharge processes, which strongly determines the battery performance. A cobalt-modified δ-MnO2 with a redox-active surface shows superior self-recovery capability as a cathode. The cobalt-containing species in the cathode enable efficient self-recovery by continuously catalyzing the electrochemical deposition of active Mn compound, which is confirmed by characterizations of both practical coin-type batteries and a new-design electrolyzer system. Under optimized condition, a high specific capacity over 500 mAh g−1 is achieved, together with a decent cycling performance with a retention rate of 63% over 5,000 cycles. With this cobalt-facilitated deposition effect, the battery with low concentration (0.02 M) of additive Mn2+ in the electrolyte (only 12 atom % to the overall Mn) maintains decent capacity retention., Graphical Abstract, Highlights • Key factor of capacity retention: active Mn compound deposition rate • A novel cobalt-catalyzed deposition strategy and the dynamic cobalt movement • Excellent performance (>500 mAh g−1) and retention (63%) over 5,000 cycles • Improvement of cycling stability with minimized Mn2+ additive, Catalysis; Electrochemical Energy Storage; Electrochemical Materials Science

The practical application of single atom catalysts (SACs) is constrained by the low achievable loading of single metal atoms. Here, nickel SACs stabilized on a nitrogen-doped carbon nanotube structure (NiSA-N-CNT) with ultrahigh Ni atomic loading up to 20.3 wt % have been successfully synthesized using a new one-pot pyrolysis method employing Ni acetylacetonate (Ni(acac)2) and dicyandiamide (DCD) as precursors. The yield and formation of NiSA-N-CNT depends strongly on the Ni(acac)2/DCD ratio and annealing temperature. Pyrolysis at 350 and 650 °C led to the formation of Ni single atom dispersed melem and graphitic carbon nitride (Ni-melem and Ni-g-C3N4). Transition from a stacked and layered Ni-g-C3N4 structure to a bamboo-shaped tubular NiSA-N-CNT structure most likely occurs via a solid-to-solid curling or rolling-up mechanism, thermally activated at temperatures of 700–900 °C. Extended X-ray absorption fine structure (EXAFS) experiments and simulations show that Ni single atoms are stabilized in the N-C...

Unreliable energy supply and environmental pollution are two major concerns of the human society in this century. Herein, we report a rational approach on preparation of hierarchically-structured cobalt-carbon composites with tunable properties for a number of applications. A facile hydrothermal treatment of cobalt nitrate and sucrose results in the formation of a metallic cobalt-amorphous carbon composite with cobalt nanospheres anchored homogenously on an amorphous carbon substrate. Tuning the calcination conditions in air will generate either a metallic cobalt-cobalt oxide core-shell structure with magnetism or a fully oxidized Co3O4 composite. The different materials are demonstrated as anodes for lithium-ion batteries (LIBs) and catalysts for advanced oxidation-based wastewater remediation. A fully oxidized composite (FC@CS, fully oxidized Co loaded on carbon spheres) as a LIB anode exhibits superior electrochemical performance, possessing a high reversible capacity, high initial columbic efficiency, outstanding cycling performance and excellent rate capability. The anode performance is superior to most reported Co3O4-based electrodes. Meanwhile, the partially oxidized composite (PC@CS, partially oxidized Co loaded on carbon spheres) functions as an efficient and stable catalyst for removal of phenol via peroxymonosulfate (PMS) activation, which is demonstrated via electron paramagnetic resonance (EPR) and quenching experiments for generation of radicals. More importantly, the recycled PC@CS can be further applied as a LIBs anode after full oxidation regeneration, performing comparably to FC@CS. This FC@CS → PC@CS → FC@CS transformation provides an innovative approach for efficient material synthesis, recycling and application.

Further to previous work on a seawater ligand mimetic calibration system for the electroanalysis of iron(III) in seawater using the iron chalcogenide glass ion-selective electrode (ISE), this study utilized alternative blends of synthetic ligands, in order to fine-tune and optimize the calibration response characteristics of this sensor for the electroanalysis of free iron(III) in seawater. Herein, an alternative calibration system (ACS) was derived using a mixture of 10 −4 M iron(III) chloride, 10 −4 M ethylenediaminetetraacetic acid (EDTA), 10 −3 M copper(II) sulphate, 5 × 10 −3 M ethylenediamine (EN) and 0.60 M sodium chloride yielding a Nernstian response of about 30 mV decade −1 . The electroanalysis of free iron(III) in seawater using the ACS generated a free iron(III) level commensurate with the predicted organic and inorganic speciation of iron(III) in seawater. Furthermore, electrochemical impedance spectroscopy (EIS), synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy have demonstrated that the surface reaction processes of this membrane in the ACS are comparable to those experienced in a natural seawater matrix. Ultimately, this study demonstrated that the ACS can mimic the surface chemistry and concomitant potentiometric response characteristics of the iron(III) sensor in seawater, enabling reliable electroanalyses of free iron(III) in seawater.

Rechargeable Zn-air battery is limited by the sluggish kinetics and poor durability of the oxygen catalysts. In this Research Article, a new bifunctional oxygen catalyst has been developed through embedding the ultrafine NiFeO nanoparticles (NPs) in a porous amorphous MnO

Despite the tremendous potential applications of hollow micro/nanostructures, their composition has been limited to mainly single chemical compounds. Inspired by recent innovations in the areas of metal organic frameworks (MOFs) and nanocoating, here, we report the rational synthesis of mesoporous ZnTiO3/TiO2 hollow polyhedra (MZTHP) obtained by hydrothermal treatment of zeolitic imidazolate framework-8 (ZIF-8)@TiO2 core–shell polyhedral particles. The subsequent calcination of these particles caused phase transformation from TiO2 to ZnTiO3 and eventually induced the formation of Zn2TiO4. In addition, the fabrication of these hollow structures revealed a way for the preparation of hollow polyhedral photocatalysts with Pt nanoparticles deposited onto their external surface (PHS-1) or encapsulated inside their hollow structures (PHS-2). Importantly, these two types of Pt-decorated nanoparticles are shown to exhibit an improved yet distinctly different performance for photocatalytic hydrogen production, highlighting that the photocatalytic activity correlates with the Pt location and dispersion.

Single-atom catalysts (SACs) are attracting significant attention due to their exceptional catalytic performance and stability. However, the controllable, scalable, and efficient synthesis of SACs remains a significant challenge. Herein, a new and versatile seeding approach is reported to synthesize SACs supported on different 2D materials such as graphene, boron nitride (BN), and molybdenum disulfide (MoS2). This method is demonstrated on the synthesis of Ni, Co, Fe, Cu, Ag, Pd single atoms as well as binary atoms of Ni and Cu codoped on 2D support materials with the mass loading of single atoms in the range of 2.8-7.9 wt%. In particular, the applicability of the new seeding strategy in electrocatalysis is demonstrate on nickel SACs supported on graphene oxide (SANi-GO), exhibiting excellent catalytic performance for electrochemical CO2 reduction reaction with a turnover frequency of 325.9 h(-1) at a low overpotential of 0.63 V and high selectivity of 96.5% for CO production. The facile, controllable, and scalable nature of this approach in the synthesis of SACs is expected to open new research avenues for the practical applications of SACs.

This paper presents the results from the investigation of arsenopyrite oxidation via mechano-chemical activation, using a stirred mill. Water and hydrogen peroxide were chosen as the lixiviant and oxidant, respectively, and maintained at a relatively low temperature (50 °C). The milling media size, mill speed, slurry percent solids and amount of H2O2 added were all kept constant throughoust these experiments. The only operational variable for this investigation was the milling time, which results in increasing levels of specific energy provided by the mill. The products of activated arsenopyrite are characterised in terms of phase composition, particulate and structural characteristics, along with reactivity. Mechano-chemical activation of arsenopyrite under oxidizing conditions shows a maximum dissolution of around 9 wt% for iron and 7 wt% for arsenic after 2 h of milling. After 3 h of milling, the main phase present is found to be amorphous in nature.

Iron single atom catalysts (Fe SACs) are the best‐known nonprecious metal (NPM) catalysts for the oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cells (PEMFCs), but their practical application has been constrained by the low Fe SACs loading (2 nanoparticle‐doped phosphoric acid/polybenzimidazole (PA/PBI/SiO2) composite membrane cells utilizing a FeSA‐G cathode with Fe SAC loading of 0.3 mg cm−2 delivers a peak power density of 325 mW cm−2 at 230 °C, better than 313 mW cm−2 obtained on the cell with a Pt/C cathode at a Pt loading of 1 mg cm−2. The cell with FeSA‐G cathode exhibits superior stability at 230 °C, as compared to that with Pt/C cathode. Our results provide a new approach to developing practical NPM catalysts to replace Pt‐based catalysts for fuel cells.

Two N-donor-functionalised ionic liquids (ILs), 1-ethyl-1,4-dimethylpiperazinium bis(trifluoromethylsulfonyl)amide (1) and 1-(2-dimethylaminoethyl)-dimethylethylammonium bis(trifluoromethylsulfonyl)amide (2), were synthesised and their electrochemical and transport properties measured. The data were compared with the benchmark system, N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (3). Marked differences in thermal and electrochemical stability were observed between the two tertiary-amine-functionalised salts and the non-functionalised benchmark. The former are up to 170 K and 2 V less stable than the structural counterpart lacking a tertiary amine function. The ion self-diffusion coefficients (Di ) and molar conductivities (Λ) are higher for the IL with an open-chain cation (2) than that with a cyclic cation (1), but less than that with a non-functionalised, heterocyclic cation (3). The viscosities (η) show the opposite behaviour. The Walden [Λ[proportionality](1/η)(t) ] and Stokes-Einstein [Di /T)[proportionality](1/η)(t) ] exponents, t, are very similar for the three salts, 0.93-0.98 (±0.05); that is, the self-diffusion coefficients and conductivity are set by η. The Di for 1 and 2 are the same, within experimental error, at the same viscosity, whereas Λ for 1 is approximately 13% higher than that of 2. The diffusion and molar conductivity data are consistent, with a slope of 0.98±0.05 for a plot of ln(ΛT) against ln(D+ +D- ). The Nernst-Einstein deviation parameters (Δ) are such that the mean of the two like-ion VCCs is greater than that of the unlike ions. The values of Δ are 0.31, 0.36 and 0.42 for 3, 1 and 2, respectively, as is typical for ILs, but there is some subtlety in the ion interactions given 2 has the largest value. The distinct diffusion coefficients (DDC) follow the order D(d)__ < D(d)++ < D(d)+_, as is common for [Tf2N](-) salts. The ion motions are not correlated as in an electrolyte solution: instead, there is greater anti-correlation between the velocities of a given anion and the overall ensemble of anions in comparison to those for the cationic analogue, the anti-correlation for the velocities of which is in turn greater than that for a given ion and the ensemble of oppositely charged ions, an observation that is due to the requirement for the conservation of momentum in the system. The DDC also show fractional SE behaviour with t~0.95.

Resistivities of thin polymer films increase abruptly with decreasing thickness, although the corresponding decline in resistance plateaus below a certain thickness. One can jump to the incorrect conclusion that quantum confinement and surface scattering are responsible for this behaviour, and we highlight the pitfalls of committing such an error.

Further to previous work on the ion-selective electrode (ISE) comprising a poly(3,4-ethylenedioxythiophene:poly(styrene sulfonate) [PEDOT : PSS] solid-contact (SC) and a plasticised polyvinyl chloride (PVC) membrane that led to blurring of interference fringes in neutron reflectometry (NR) data, the lipophilic polymethyl methacrylate/polydecyl methacrylate (PMMA-PDMA) copolymer ISE membrane was used to provide high quality NR data that is relatively free of interfacial roughening and unequivocal information on the uptake of water in this important SC ISE. The outcomes revealed that the hydrophobic PMMA-PDMA membrane remains free of absorbed water, while the underlying the PEDOT : PSS SC absorbs water, swelling and changing its neutron scattering properties.