Structure transformation induced bi-component Co–Mo/A-Co(OH)2 as highly efficient hydrogen evolution catalyst in alkaline media
Yingqing Ou, Lu Liu, Xiao Peng, Lili Zhang, Zhongwen Ou, Wendong Zhang, Yunhuai Zhang
Abstract
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.