Bi-metallic cobalt-nickel phosphide nanowires for electrocatalysis of the oxygen and hydrogen evolution reactions

Transition metal phosphides (TMPs) have emerged as a new class of electrocatalysts capable of catalyzing the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) with high efficiency and good stability. Here, we report a facile fabrication of a series of cobalt-nickel phosphide nanowires (CoNiP NWs) containing different compositions of Co and Ni, which is accomplished by hydrothermal growth of cobalt-nickel-carbonate-hydroxide NWs and a subsequent post-phosphorization treatment. We investigate and compare the electrocatalytic performance of the CoNiP NWs for the OER and HER in alkaline solution. The results show that CoNiP NWs with equimol Co and Ni, i.e. CoNiP-1:1, show the best apparent and intrinsic activities for both OER and HER, compared to CoNiP NWs with other Co/Ni ratios as well as the mono-metallic CoP and Ni5P4 controls. The CoNiP-1:1 can deliver the benchmark apparent current density of 10 mA cm(-2) at an overpotential of 301 and 252 mV for the OER and the HER, respectively, and show good stability over 24 h without obvious degradation, holding substantial promise for use as an effective and inexpensive alternative in alkaline water electrolysis.