Hierarchical Cu3P-based nanoarrays on nickel foam as efficient electrocatalysts for overall water splitting

Exploring the efficient bifunctional catalysts and binder-free electrode materials for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is receiving continuous interest. Herein, we report the fabrication of hierarchical copper phosphide nanoarrays (Cu3P) on three-dimensional (3D) nickel foam (NF) through a template-directed synthetic strategy as electrocatalysts for overall water splitting. Specifically, the Cu3P/NF electrode demonstrates a remarkably low overpotential of ∼331 mV to approach the current density of 50 mA cm−2 in the OER, and an overpotential of ∼115 mV to achieve −10 mA cm−2 current density in the HER. Meanwhile the Cu3P/NF catalyst could hold a great stability for both reactions in alkaline condition, reflected in 37 h for OER and 24 h for HER of consistent galvanostatic electrolysis. As revealed by TEM, STEM and XPS characterizations, the high catalytic OER activity can be ascribed to the 3D open structure of Cu3P/NF and the abundant CuO active sites in hierarchical CuO/Cu3P/NF structure after in-situ activation. Furthermore, the overall water splitting is conducted in a two-electrode cell, which requires only a cell voltage of 1.63 V to approach 10 mA cm−2 with a good stability of 20 h. This protocol of Cu3P/NF electrode affords a general strategy to construct hierarchically structured metal phosphides for clean energy-related application.