Efficient generation of H2 via water-splitting is an underpinning technology for realizing the hydrogen economy. However, the sluggish anodic oxygen evolution reaction (OER) requires large energy input. Low-cost, transition metals...

Nickel-based catalysts are most commonly used in industrial alkaline water electrolysis. However, it remains a great challenge to address the sluggish reaction kinetics and severe deactivation problems of hydrogen evolution reaction (HER). Here, we show a Cu-doped Ni catalyst implanted with Ni-O-VOx sites (Ni(Cu)VOx) for alkaline HER. The optimal Ni(Cu) VOx electrode exhibits a near-zero onset overpotential and low overpotential of 21 mV to deliver-10 mA cm −2 , which is comparable to benchmark Pt/C catalyst. Evidence for the formation of Ni-O-VOx sites in Ni(Cu)VOx is established by systematic X-ray absorption spectroscopy studies. The VOx can cause a substantial dampening of Ni lattice and create an enlarged electrochemically active surface area. First-principles calculations support that the Ni-O-VOx sites are superactive and can promote the charge redistribution from Ni to VOx, which greatly weakens the H-adsorption and H 2 release free energy over Ni. This endows the Ni(Cu)VOx electrode high HER activity and long-term durability.

Nonprecious NiFe and CoFe oxyhydroxides are among the most active materials for oxygen evolution reaction (OER) in basic media. However, the phase separation in these composites during water oxidation remains a critical issue that often results in degradation of electrochemical performance and debate on the mechanism and the active intermediates. In this study, we show that the introduction of Cr can efficiently transform the crystalline multiphase NiFe and CoFe oxides/ hydroxides into homogeneous amorphous nanodots with sharply reduced nanoparticle size from tens of nanometers to merely 2−3 nm. Serving as an OER catalyst, the ternary NiFeCr and CoFeCr catalysts exhibit a smaller onset potential of ∼1.51 V vs reversible hydrogen electrode (RHE) and a stable OER performance during long-term water electrolysis. The impact of Cr on the NiFe and CoFe catalysts for OER kinetics was systematically investigated by operando electrochemical Raman spectroscopy. It is found that, for the NiFeCr compound, Cr can promote the generation of a more active β-NiOOH phase than that of the NiFe composite during water oxidation. For the CoFe and CoFeCr systems, the introduction of Cr only disturbs the lattice crystallization. However, active CoOOH is spontaneously present on the surface of the composites upon making contact with KOH electrolyte, even without applying a potential. Thus, Co-based catalysts can easily achieve the "ready-to-serve" state for high-performance water oxidation without preactivation.

By introducing chromium into a nickel-iron layered double hydroxide (LDH), a nickel iron chromium hydroxide nanomesh catalyst has been achieved on nickel foam substrate via electrodeposition followed by partial etching of chromium. The electrodeposited chromium acts as a sacrificial template to introduce holes in the LDH to increase the electrochemically active surface area, and the remaining chromium synergistically modulates the electronic structure of the composite. The obtained electrode shows extraordinary performance for oxygen evolution reaction and excellent electrochemical stability. The onset potential of the as-prepared electrode in 1 M KOH is only 1.43 V vs RHE, and the overpotential to achieve a high current density of 100 mA·cm is only 255 mV, outperforming benchmark nonprecious NiFe hydroxide composite electrode in alkaline media.

Nickel-heteroatoms bridge sites are important reaction descriptors for many catalytic and electrochemical processes.Herein we report the controllable surface modification of nickel-nitrogen (NiÀN) bridge sites on metallic Ni particles via asimplified vapor-assisted treatment approach. Xray absorption spectroscopy( XAS) and Operando Raman spectroscopyv erifies the interaction between Ni and surfaceanchored N, whichl eads to distorted Ni lattice structure with improved wettability.T he NiÀNb ridge sites with appropriate Ncoveragelevel plays acritical role in the enhanced hydrogen evolution reaction (HER) and the optimizede lectrode (NiÀ N 0.19 )has demonstrated superior HER performances with low overpotential merely of 42 mV for achieving ac urrent density of 10 mA cm À2 ,a sw ell as favorable reaction kinetics and excellent durability in alkaline electrolyte.D FT calculations revealed that the appropriate N-coverage level can lead to the most favorable DG H* kinetics for both adsorption of H* and release of H 2 ,w hile high Nc overage (NiÀN 0.59 )r esults in weaker H* adsorption, thus ad ecreased HER activity, corresponding well to our experimental observations.Furthermore,t his generic synthetic approach can also be applied to prepare S-modified Ni HER catalyst by generating hydrogen sulfide vapor.Nickel is an ideal non-noble metal catalyst for many key industrial applications ranging from water electrolysis,chloralkali reactions,tophotoelectrochemical water splitting. [1] To al arge extent, the performance of Ni is determined by the chemical structure of outer or sublayer atoms around Ni particles that directly interact with reactant species.C onsequently,s urface modification of Ni represents an important strategy to tune its chemical and structural properties for achieving enhanced catalytic performances.T raditionally,N i has been modified with heteroatoms such as Oand Stoform corresponding oxides and sulfides;h owever, their performances are still far from satisfactory.Most recently,significant interest has been aroused to heteroatoms beyond Oand S, for example,Natoms.Both theoretical and experimental studies revealed that the as-formed Ni À Nb ridge sites can adsorb various reagent species such as hydroxyl, water, and carbon dioxide,a nd the charge transfer between them is usually the rate-determining step (RDS) of many reactions.For example, Bao and co-workers reported the formation of molecular Ni À Nc omplex that demonstrated excellent performances for catalytic CO 2 reduction reactions. [2] Antonietti and co-workers fabricated 3D Ni nitride on Ni foam for HER in alkaline media. [3] Despite these developments,s everal key challenges remain in this research direction:( i) Ther ational manipulation of Ni À Nb ridges sites with different Nc overage on Ni surfaces for satisfying different catalytic reactions to achieve optimal performances.( ii)M ost synthetic procedures for generating NiÀNbridges sites,like pyrolysis [2,3] and ammonia annealing, [4] require harsh and complicated experimental conditions an...