N-doped carbon nanowire array confined cobalt phosphides as efficient bifunctional electrocatalysts for water splitting

Abstract

Cobalt phosphides (CoP) are considered as ideal bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) under alkaline condition. However, their performance and stability are significantly limited by their low conductivity and severe surface reconstitution. To counter this, herein, a copper foam supported N-doped carbon nanowire array confined CoP nanoparticle hybrid (CoP@NCNWAs/CF) as an efficient bifunctional electrocatalyst for overall water splitting (OWS) is prepared by an impregnation–cation exchange–phosphating strategy. Theoretical and experimental results verify that NCNWAs can not only boost electron transfer and regulate the electronic structure of CoP, but also suppress excessive surface reconstruction to form CoOOH during the OER process, thus enhancing the electroactivity and stability of the HER and OER. As a result, the as-prepared CoP@NCNWAs/CF exhibits outstanding catalytic electroactivity towards the HER and OER, including low overpotentials of 166 and 287 mV at a current density (j) of 100 mA cm⁻², respectively. Moreover, a CoP@NCNWAs/CF-based electrolyzer delivers a j of 400 mA cm⁻² at a cell voltage of only 1.83 V, even surpassing commercial Pt + RuO₂ catalysts. This work provides guidance for further design of high-performance CoP-based electrocatalysts.