Interfacial Engineering of Ni3N/Mo2N Heterojunctions for Urea-Assisted Hydrogen Evolution Reaction

The urea oxidation reaction (UOR) is considered as an alternative to the oxygen evolution reaction for high-efficiency hydrogen production. However, an urea molecule is relatively complex, containing both electron-donating amino (-NH2) and electron-withdrawing carbonyl (C=O) groups, and understanding the influence of different functional groups on the adsorption behavior is conducive to the rational design and preparation of high-performance UOR catalysts. Herein, we report a simple synthesis of the Ni3N/Mo2N heterostructure and a systematic investigation of urea-assisted electrolytic hydrogen production. Both temperature-programmed desorption and theoretical calculations decipher that -NH2 and C=O groups of the urea molecule are more easily adsorbed on Ni3N and Mo2N, respectively. Meanwhile, the Ni3N/ Mo2N heterostructure could combine and enhance the advantages of individual components, optimizing the adsorption of urea. Besides, this heterostructure is also beneficial to improving the hydrogen evolution reaction performance. As expected, in the two-electrode urea-assisted water electrolyzer utilizing Ni3N/Mo2N as bifunctional catalysts, hydrogen production can readily occur at an evidently lower voltage (1.36 V@10 mA cm-2), which is much lower than that of traditional water electrolysis, as well as 7 times higher hydrogen production rate is achieved.

Automated summary

This study demonstrates a simple synthesis of the Ni3N/Mo2N heterostructure and investigates urea-assisted electrolytic hydrogen production. The adsorption behavior of the urea molecule is analyzed, showing that -NH2 groups preferentially adsorb on Ni3N while C=O groups preferentially adsorb on Mo2N. The Ni3N/Mo2N heterostructure optimizes urea adsorption and enhances the hydrogen evolution reaction, leading to significantly lower voltage requirements and a 7 times higher hydrogen production rate in the urea-assisted water electrolyzer.