Chestnut-like Copper Cobalt Phosphide Catalyst for All-pH Hydrogen Evolution Reaction and Alkaline Water Electrolysis
A novel type of chestnut-like copper cobalt phosphide (CuxCo1-xP) nanoarrays on carbon fiber paper (CP) for the splitting of water are synthesized through a simple hydrothermal followed by in situ phosphorization treatment. As a hydrogen evolution reaction (HER) catalyst, the CuxCo1-xP/CP shows high HER activity at all PH values. To drive a current density of 10 mA cm-2, the optimized Cu0.075Co0.925P/CP with an overpotential of 47, 120, and 70 mV in acidic, neutral, and alkaline media, respectively. In addition, the Cu0.075Co0.925P/CP exhibits excellent activity for oxygen evolution reaction (OER) with a small overpotential of 221 mV to reach 10 mA cm-2. Furthermore, when Cu0.075Co0.925P/CP used as both the cathode and anode for overall water splitting in 1.0 M KOH, a two-electrode electrolyzer needs only a cell voltage of 1.55 V to achieve 10 mA cm-2, superior to noble metal-based Pt/C||IrO2 cell and most previously reported electrocatalysts. Moreover, this electrolyzer can be powered by a single AA battery with a voltage of 1.5 V. The density functional theory (DFT) calculations further evidence that the good catalytic activity of CuxCo1-xP/CP resulted from the smaller hydrogen adsorption free energy (ΔGH*) and overpotential. This work provides a promising strategy to design high-performance and low-cost electrocatalysts for overall water splitting and other energy-related applications.