Freestanding (Ni₄Zn)_0.8 Intermetallic Nanosheets as Bifunctional Electrocatalysts for Urea-Assisted Hydrogen Production

The electrochemical oxidation of urea provides an efficient and energy-saving method for the treatment of wastewater containing urea along with hydrogen production. However, it is crucial to develop electrocatalysts possessing both high electrocatalytic activity and long-term stability. In this study, a (Ni4Zn)0.8 intermetallic catalyst is deposited on nickel foam (labeled as (Ni4Zn)0.8/NF) by a rapid one-step electrodeposition technique. The as-deposited intermetallic catalyst can facilitate the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) simultaneously, displaying obvious bifunctional characteristics. Benefiting from metal–metal electronic modulation, the (Ni4Zn)0.8/NF integral electrode exhibits a low overpotential of 45 mV at −10 mA cm–2 with a small Tafel slope of 54.35 mV dec–1 in 1 M KOH solution for the HER; meanwhile, the as-obtained electrode requires only 1.40 V voltage to achieve the current density of 100 mA cm–2 in 1 M KOH with 0.5 M urea. Employing the as-prepared (Ni4Zn)0.8/NF electrode as the anode and cathode simultaneously, the urea-assisted water electrolysis device (HER||UOR system) exhibits a voltage reduction of 258 mV against the conventional water electrolysis device (HER||OER system), which offers a catalyst selection for the HER||UOR in practical application.