A universal method to fabricate high-valence transition metal-based HER electrocatalysts and direct Raman spectroscopic evidence for interfacial water regulation.

Valence modulation of transition metal oxides represents a highly effective approach in designing high-performance catalysts, particularly for pivotal applications such as the hydrogen evolution reaction (HER) in solar/electric water splitting and the hydrogen economy. Recently, there has been a growing interest in high-valence transition metal-based electrocatalysts (HVTMs) due to their demonstrated superiority in HER performance, attributed to the fundamental dynamics of charge transfer and the evolution of intermediates. Nevertheless, the synthesis of HVTMs encounters considerable thermodynamic barriers, which presents challenges in their preparation. Moreover, the underlying mechanism responsible for the enhancement in HVTMs still needs to be discovered. Hence, the universal synthesis strategies of the HVTMs are discussed, and direct Raman spectroscopic evidence for intermediates regulation is revealed to guide the further design of the HVTM electrocatalysts. This work offers new insights for facile designing of HVTMs electrocatalysts for energy conversion and storage through adjusting the reaction pathway.

Tunable d-band center of a NiFeMo alloy with enlarged lattice strain enhancing the intrinsic catalytic activity for overall water-splitting.

Developing efficient bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) under alkaline conditions is prospective for reducing energy consumption during water electrolysis. In this work, we successfully synthesized nanocluster structure composites composed of NiFeMo alloys with controllable lattice strain by the electrodeposition method at room temperature. The unique structure of NiFeMo/SSM (stainless steel mesh) facilitates the exposure of abundant active sites and promotes mass transfer and gas exportation. The NiFeMo/SSM electrode exhibits a low overpotential of 86 mV at 10 mA cm-2 for the HER and 318 mV at 50 mA cm-2 for the OER, and the assembled device reveals a low voltage of 1.764 V at 50 mA cm-2. Moreover, both the experimental results and theoretical calculations reveal that the dual doping of Mo and Fe can induce the tunable lattice strain of nickel, which in turn changes the d-band center and electronic interaction of the catalytically active site, and finally enhances the HER and OER catalytic activity. This work may provide more options for the design and preparation of bifunctional catalysts based on non-noble metals.