Porous NiCo alloy thin sheets with synergistic Co/Ni sites for high-efficiency urea-assisted electrocatalytic hydrogen production

Abstract

The optimization of electronic structure and increase of exposed surface sites represent the promising direction for enhancing the activity of Ni-based catalysts for urea oxidation reaction (UOR)-assisted electrolysis. Here, we have reported the designed synthesis of 2D porous NiCo alloy thin sheets (NiCo/C) based on NaCl-induced transformation of the EDTA-NiCo complex for effective UOR-assisted hydrogen evolution reaction (HER). The porous and thin-sheet structure endows a large specific surface area of 141.59 m2/g, greatly enhancing the exposure of active sites. The electron transfer from Co to Ni can optimize the electronic properties of Ni sites, decreasing energy barrier and accelerating reaction kinetics for UOR. The catalyst shows low UOR potential of 1.30 V at a current density of 10 mA cm-2, much lower than the traditional oxygen evolution reaction (1.51 V). The in-situ impedance/infrared spectroscopy indicates the fast UOR process and a more environmentally sustainable "carbonate" pathway. The catalyst also shows low HER overpotential of 30 mV at a current density of 10 mA cm-2, being comparable to Pt/C. The urea-assisted H2 production cell based on NiCo/C only requires 1.38 V at a current density of 10 mA cm-2, superior to the 1.45 V of Pt/C‖RuO2 cell.