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Water electrolysis has been considered as a green and sustainable technique for hydrogen production, while the sluggish kinetics of the oxygen evolution reaction (OER) and the insufficient active sites remain bottlenecks for practical performance. Herein, we present in situ electrochemical activation of nickel (Ni) alloys for water splitting assisted by the electro-oxidation of organic molecules. It has been discovered that in situ electrochemical activation results in an increased degree of metal oxidation, thereby inducing more high-valence active metal species (NiOOH). These species not only function as active sites for surface adsorption but also facilitate electron transfer. Subsequently, two representative organic molecules, methanol and ethanol, are introduced to further promote the water electrolysis. Through a combination of electrochemical testing and in situ Raman spectroscopy, it has been revealed that the activated Ni alloy demonstrates a stronger response to the adsorbed alcohol molecules and tends to form β-NiOOH at lower potentials compared to the pristine one, resulting in enhanced water splitting. The present work advances a simple activation method for transition metal-based electrocatalysts for highly efficient alcohol oxidation-assisted water electrolysis. [ABSTRACT FROM AUTHOR]

Electrocatalytic activities of electrodes for water splitting generally are assessed in terms of current density normalisation on the basis of geometric area. However, this approach does not involve the effects of surface microstructure which often is rough. The present work examines this disagreement through the electrochemical characterisation of thermally treated carbon fibre paper in which the current density is normalised comparatively by geometric area, BET specific surface area and electrochemical active surface area (ECSA). The results show that the geometric area provides a nominal means of assessing the electrocatalytic activity. Since BET is effective in assessing the physical surface area, it provides a superior indication. However, ECSA provides the most discriminating means of assessment and reflects the intrinsic electrochemical activity. [ABSTRACT FROM AUTHOR]

Nickel‐heteroatoms bridge sites are important reaction descriptors for many catalytic and electrochemical processes. Herein we report the controllable surface modification of nickel–nitrogen (Ni−N) bridge sites on metallic Ni particles via a simplified vapor‐assisted treatment approach. X‐ray absorption spectroscopy (XAS) and Operando Raman spectroscopy verifies the interaction between Ni and surface‐anchored N, which leads to distorted Ni lattice structure with improved wettability. The Ni−N bridge sites with appropriate N coverage level plays a critical role in the enhanced hydrogen evolution reaction (HER) and the optimized electrode (Ni−N0.19) has demonstrated superior HER performances with low overpotential merely of 42 mV for achieving a current density of 10 mA cm−2, as well as favorable reaction kinetics and excellent durability in alkaline electrolyte. DFT calculations revealed that the appropriate N‐coverage level can lead to the most favorable ΔGH* kinetics for both adsorption of H* and release of H2, while high N coverage (Ni−N0.59) results in weaker H* adsorption, thus a decreased HER activity, corresponding well to our experimental observations. Furthermore, this generic synthetic approach can also be applied to prepare S‐modified Ni HER catalyst by generating hydrogen sulfide vapor. Controllable surface modification of nickel–nitrogen (Ni−N) bridge sites is prepared via a simplified vapor‐assisted treatment approach. The N modified Ni with distorted structures and suitable N coverage level significantly promotes hydrogen evolution reaction in alkaline conditions. [ABSTRACT FROM AUTHOR]

The present work reports data for the mineralogical, nanostructural, optical, and photocatalytic properties of Cr-doped, V-doped, and Cr/V-codoped TiO2 nanoparticles in terms of the effects of doping level and associated particle size on their photocatalytic performance. The photocatalytic performance of doped TiO2 is dependent not only on the particle size at low-doping levels but also on both the type and amount of dopant(s) at high-doping levels. These data illustrate the existence of two clear regimes in behaviour and enable the introduction of a new interpretation of the causes of these effects. At ultralow and low-doping levels, extrinsic effects (viz., particulate characteristics) determine the performance. At high-doping levels, intrinsic effects (viz., dopant-controlled chemical and electrical characteristics) determine the performance. In the intermediate range of medium-doping levels, the performance shows the mixed effects of these two factors. A schematic model comprehensively summarizing the role of doping in these extrinsic and intrinsic effects on the photocatalytic process is presented. Further, a phenomenological model that identifies the regions of dominance of these effects as a function of particle size and doping level on the photocatalytic performance is proposed. These generic models assist in both understanding the systematic effects of doping on photocatalysts and identifying approaches for modification. [ABSTRACT FROM AUTHOR]

In this work, a surface sulfurization strategy is utilized to construct Co3O4@CoSx heterogeneous catalysts with a highly efficient activity towards the oxygen evolution reaction (OER), and the enhanced catalytic activity is dependent on the degree of surface sulfurization. It is found that forming amorphous CoSx on the Co3O4 surface through surface anion exchange can effectively generate more Co2+ ions and oxygen vacancies in the lattice structure, not only inducing the production of more CoOOH but also facilitating water adsorption during the water oxidation process. [ABSTRACT FROM AUTHOR]