A Highly Active and Robust Copper-Based Electrocatalyst toward Hydrogen Evolution Reaction with Low Overpotential in Neutral Solution

Although significant progress has been made recently, copper-based materials have long been considered to be ineffective catalysts toward the hydrogen evolution reaction (HER), in most cases, requiring high overpotentials more than 300 mV. We report here that a Cu(0)-based nanoparticle film electrodeposited in situ from a Cu(II) oxime complex can act as a highly active and robust HER electrocatalyst in neutral phosphate buffer solution. The as-prepared nanoparticle film is of poor crystallization, which incorporates significant amounts of oxime ligand residues and buffer anions PO 4 3– . The proposed mechanism suggests that the Cu(0)-based nanoparticle film is activated with incorporated or adsorbed PO 4 3– anions and the PO 4 3– anions-anchored sites might serve as the actual catalytic active sites with efficient proton transport mediators. Catalysis occurs with a low onset overpotential (η) of 65 mV, and a current density of 1 mA/cm 2 can be achieved with η = 120 mV. The nanoparticle film shows an excellent catalytic durability with slightly rising current density during electrolysis, presumably due to further incorporation or adsorption of PO 4 3– anions in the process. This electrocatalyst not only forms in situ from earth-abundant materials but also operates in neutral water with low overpotential and high stability.