Synergistic Effect between Co<sub>2</sub>P/Fe<sub>2</sub>P Nanoparticles and NiFe Layered Double Hydroxides Promotes Urea Oxidation Reaction-Assisted Hydrogen Production
Lili Wang, Wurigamula He, Duanduan Yin, Qianli Ma, Wensheng Yu, Ying Yang, Xiangting Dong
Abstract
Urea oxidation reaction (UOR) can replace the anode oxygen evolution reaction (OER) of overall water splitting. Compared with the OER, UOR has a lower overpotential and can significantly reduce the energy consumption of hydrogen production through water electrolysis, thus receiving widespread attention. Here, we use Co–Fe Prussian blue analogue/nickel foam (Co–Fe PBA/NF) as a precursor, and the Co–Fe PBA precursors collapse by phosphating to form a carbon layer containing Co 2 P and Fe 2 P nanoparticles and cover the NF framework (Co 2 P/Fe 2 P/NF). The carbon layer provides a limiting effect for Co 2 P and Fe 2 P nanoparticles. Subsequently, Co 2 P/Fe 2 P/NF and NiFe-LDH (iron nickel double hydroxide layer) are compounded by a hydrothermal method to obtain [Co 2 P/Fe 2 P]/NiFe-LDH/NF. A strong electronic interaction occurs at the interface of Co 2 P/Fe 2 P/NF and NiFe-LDH, resulting in a strong synergistic effect. The synergistic effect enhances the conductivity of [Co 2 P/Fe 2 P]/NiFe-LDH/NF and accelerates the reaction kinetics. Besides, Co 2 P/Fe 2 P/NF and [Co 2 P/Fe 2 P]/NiFe-LDH/NF have superhydrophilic and aerophobic structures, which promote the immersion of electrolytes and the separation of bubbles. Thus, in the presence of urea, Co 2 P/Fe 2 P/NF and [Co 2 P/Fe 2 P]/NiFe-LDH/NF electrocatalysts only require 34.4 mV and 1.38 V to drive HER (hydrogen evolution reaction) and UOR current densities of 10 and 100 mA cm –2, respectively. It is worth noting that the alkaline electrolyzer containing urea (+) [Fe 2 P/Co 2 P]/NiFe-LDH/NF||Fe 2 P/Co 2 P/NF (−) requires only a potential of 1.48 V to reach a current density of 10 mA cm –2 . Compared with water electrolysis, at the same current density, the potential of UOR-assisted hydrogen production is significantly reduced by 0.64 V. This work provides an avenue for the rational design of electrocatalysts.