NiCo-Based Heterostructure on Nickel Foam for Boosting Urea-Assisted Electrolytic Hydrogen Production

Urea-assisted electrolytic water splitting is recognized as a high-efficiency and energy-saving hydrogen production technology because of its advantages of reducing the thermodynamic electrode potential and decomposing pollutant. Furthermore, the reasonably designed heterojunction catalyst can significantly accelerate the kinetic rate of the urea oxidation reaction (UOR). In this paper, a four-component (including NiCo, NiCoP, Ni 3 Se 2, and NiSe) NiCo-based heterostructure (expressed as Ni x Se y /NC-NCP) was successfully synthesized by combining the electrodeposition method and high-temperature selenization strategy, which consists of an interlaced chainlike structure and an interconnected nanosphere structure. As expected, the Ni x Se y /NC-NCP heterostructure only requires a low potential of 1.36 V to enable the UOR to deliver a current density of 100 mA cm –2, which is 208 mV lower than that of the corresponding oxygen evolution reaction (OER). The results of physical characterizations confirm that the surface of Ni x Se y /NC-NCP was reconstructed during the electrocatalytic UOR process; that is, active species such as CoOOH and NiOOH were generated on the surface. The Pt/C||Ni x Se y /NC-NCP electrolyzer composed of commercial Pt/C and self-supporting Ni x Se y /NC-NCP is used for the urea-assisted water splitting, which only needs low cell voltages of 1.40 and 1.45 V to drive the current densities of 100 and 200 mA cm –2, respectively. This study promotes research on hierarchical heterojunction catalysts to enhance the electrocatalytic UOR performance, effectively reducing the energy required for electrochemical hydrogen production.