Nickel phosphide nanoarrays decorated on amorphous NiPOx/Fe(OH)3: A stable core–shell electrocatalyst for efficient oxygen evolution at large current density

Abstract

Severe reconstruction of transition-metal phosphides occurring in the oxygen evolution reaction (OER) process suffers from catalyst activity and long-term stability challenges. Herein, we develop a facile preoxidation tactic to fabricate an amorphous NiPOx/Fe(OH)3 protective layer on the surface of NiP nanoarrays and investigate the effect of the NiPOx/Fe(OH)3 layer thickness on electrocatalytic OER performance. We find the optimized NiP@NiPOx/Fe(OH)3 electrode achieves a promising OER performance, with a low overpotential of 270.7 mV and an ultralong durability for 500 h at 500 mA cm−2, predominantly originating from the synergy of the highly conductive NiP core and the NiPOx/Fe(OH)3 layer. Post-OER characterizations demonstrate that the NiPOx/Fe(OH)3 layer protects NiP from oxidation during the OER process and thus avoids the severe reconstruction of NiP adverse to the catalyst stability. This work opens an avenue for enhancing OER performance in water splitting via rational control of surface reconstruction of metal phosphides at the desired point.