The development of efficient and cost-effective electrocatalysts for alkaline water electrolysis is crucial for advancing hydrogen production technologies. Herein, we report the synthesis and characterization of a highly active, platinum-group-metal-free electrocatalyst for the hydrogen evolution reaction in alkaline media. The catalyst is obtained via the exsolution of Ni–Mo alloy nanoparticles anchored on MoO 2 during the reduction of a NiMoO 4 precursor grown on porous nickel substrates. It demonstrates high catalytic activity, achieving benchmark performance with an overpotential of −89 mV and a cell voltage of 1.71 V at a current density of 1 A/cm 2 . Electrochemical testing, including operation at high current densities under industrially relevant conditions (80 °C, 30 wt % KOH, flowing electrolyte), validates its suitability for large-scale applications. Importantly, structural analysis reveals the presence of Ni-rich Ni 10 Mo particles on MoO 2 rather than the often-proposed Ni 4 Mo alloy, providing insight into the actual active phase of Ni–Mo catalysts. This distinction advances the fundamental understanding of Ni–Mo chemistry and offers guidance for the rational design of high-performance, platinum-group-metal-free catalysts for hydrogen evolution. This publication is licensed under You are free to share (copy and redistribute) this article in any medium or format and to adapt (remix, transform, and build upon) the material for any purpose, even commercially within the parameters below: Creative Commons (CC): This is a Creative Commons license. Attribution (BY): Credit must be given to the creator. *Disclaimer This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials. You are free to share (copy and redistribute) this article in any medium or format and to adapt (remix, transform, and build upon) the material for any purpose, even commercially within the parameters below: Creative Commons (CC): This is a Creative Commons license. Attribution (BY): Credit must be given to the creator. *Disclaimer This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials. You are free to share (copy and redistribute) this article in any medium or format and to adapt (remix, transform, and build upon) the material for any purpose, even commercially within the parameters below: Creative Commons (CC): This is a Creative Commons license. Attribution (BY): Credit must be given to the creator. *Disclaimer This summary highlights only some of the key features and terms of the actual license. It is not a license and has no legal value. Carefully review the actual license before using these materials.
Müller et al. (Sun,) studied this question.