Anchoring Ni2P Sheets on NiCo2O4 Nanocone Arrays as Optimized Bifunctional Electrocatalyst for Water Splitting

Bifunctional electrocatalyst is promising for the overall water splitting with high efficiency. Herein, inspired by the superior oxygen evolution reaction (OER) performance of transition metal oxide and remarkable hydrogen evolution reaction (HER) activity of transition metal phosphide, hierarchical NiCo2O4/Ni2P core-shell nanocone array on Ni foam is synthesized. The synergetic effect between the NiCo2O4 "core" and the Ni2P "shell" results in dramatically enhanced catalytic performance. It shows higher activity and longer durability in both OER and HER than bare NiCo2O4 or Ni2P. The hierarchical NiCo2O4/Ni2P catalyst is capable of catalyzing OER with a low overpotential of 250 mV at 10 mA cm(-2) in alkaline media. Moreover, it shows excellent catalytic activity for HER to achieve 10 mA cm(-2) at a small overpotential of 45 mV. When the NiCo2O4/Ni2P is adopted as both anode and cathode in a two-electrode cell for overall water splitting, it only needs 1.59 V to reach a current density of 10 mA cm(-2). Almost no decay is observed after the electrodes work for about 50 h. The newly developed electrocatalyst combines the satisfactory working stability with outstanding catalytic activity, which paves the way for exploring overall water splitting catalysts.