Triple Functions of Ni(OH)₂ on the Surface of WN Nanowires Remarkably Promoting Electrocatalytic Activity in Full Water Splitting

Abstract

Discovering efficient and promising non-noble catalysts toward the alkaline hydrogen evolution reaction (HER) is vital for a clean energy system. Here, we design an efficient alkaline HER electrocatalyst, coating of WN nanowire core with a Ni(OH)2 shell supported on a carbon fiber paper (WN-Ni(OH)2). In a 1 M KOH solution, the hierarchical electrocatalyst affords a current density of 20 mA cm–2 at an overpotential of 170 mV and 100 mA cm–2 at 245 mV. The enhanced performance of WN-Ni(OH)2 in the HER is attributed to the synergy between WN and Ni(OH)2: during water dissociation, hydroxyl groups are preferentially adsorbed on WN and hydrogen on Ni(OH)2; meanwhile, Ni(OH)2 could promote hydroxyl group desorption from WN. Thus, the full-surface Volmer reaction kinetics could be enhanced. As a consequence, the WN-Ni(OH)2 has a reduced activation energy of the HER and enhanced intrinsic activity performance. Meanwhile, the hybrid can reach a current density of 100 mA cm–2 at an overpotential of 339 mV for the oxygen evolution reaction (OER), and an overpotential of 510 mV for the full water-splitting reaction. This interfacial cooperation offers a promising bifunctional electrocatalyst, as well as a hopeful strategy for fabricating efficient nitride-based electrocatalysts in alkaline media.