Structure transformation induced bi-component Co–Mo/A-Co(OH)2 as highly efficient hydrogen evolution catalyst in alkaline media

Elucidating the inherent origins of the sluggish hydrogen evolution reaction (HER) kinetics in alkaline media and developing high-performance electrocatalysts are fundamental for the advances of conventional alkaline water electrolyzers and emerging anion exchange membrane (AEM) electrolyzers. Here we present a facile electrochemical modification strategy for the synthesis of bi-component Co–Mo_(18%)/A-Co(OH)₂ catalyst toward efficient HER catalysis in alkaline media. Porous Co–Mo alloys with adjustable Mo/Co atomic ratio are first prepared by H₂-assisted cathodic electrodeposition. By virtue of the appropriate electronic structure and hydrogen binding energy, Co–Mo_(18%) is the most HER active among the alloys and is further activated by a constant-current electrochemical modification process. Physical characterizations reveal the formation of amorphous Co(OH)₂ nanoparticles on the surface. Electrokinetic analysis combined with theoretical calculations reveal that the in-situ formed Co(OH)₂ can efficiently promote the water dissociation, resulting in accelerated Volmer-step kinetics. As a result, the Co–Mo_(18%)/A-Co(OH)₂ simultaneously achieves the optimization of the two factors dominating alkaline HER activity, i.e., water dissociation and hydrogen adsorption/desorption via the bifunctional synergy of the bi-components. The high HER activity (η₁₀ of 47 ​mV at 10 ​mA ​cm⁻²) of Co–Mo_(18%)/A-Co(OH)₂ is close to benchmark Pt/C catalyst and comparable or superior to the most active non-noble metal catalysts.