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

Abstract

The optimization of the electronic structure and increased number of exposed surface sites represent a promising direction for enhancing the activity of Ni-based catalysts for urea oxidation reaction (UOR)-assisted electrolysis. Herein, 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 the effective UOR-assisted hydrogen evolution reaction (HER). The porous and thin-sheet structure endows a large specific surface area of 141.59 m² g⁻¹, greatly enhancing the exposure of active sites. Electron transfer from Co to Ni can optimize the electronic properties of the Ni sites, decreasing the energy barrier and accelerating the reaction kinetics for the UOR. The catalyst shows a low UOR potential of 1.30 V at a current density of 10 mA cm⁻², which is much lower than the traditional oxygen evolution reaction (1.51 V). In situ impedance/infrared spectroscopy indicates the fast UOR process and a more environmentally sustainable “carbonate” pathway. The catalyst also shows a low HER overpotential of 30 mV at a current density of 10 mA cm⁻², being comparable to Pt/C. A urea-assisted H² production cell based on NiCo/C requires only 1.38 V at a current density of 10 mA cm⁻², which is superior to the Pt/C∥RuO₂ cell (1.45 V).