Accelerating the generation of NiOOH by in-situ surface phosphating nickel sulfide for promoting the proton-coupled electron transfer kinetics of urea electrolysis
Xin Guo, Longyu Qiu, Menggang Li, Fenyang Tian, Xue Ren, Jie Sheng, Shuo Geng, Guanghui Han, Yarong Huang, Ying Song, Weiwei Yang, Yongsheng Yu
Abstract
Nickel sulfide (Ni 3 S 2 ) is a highly promising electrocatalyst for urea oxidation reaction (UOR), and NiOOH formed by the surface phase transition of Ni 3 S 2 during UOR is the ideal catalytic active species. However, the strong covalent bonds of Ni 3 S 2 hinders the generation of NiOOH, limiting the further improvement of UOR activity. Herein, the Ni 3 S 2 @Ni 3 P core–shell nanorods have been constructed by an in-situ surface phosphating method to boost UOR performance, realizing high catalytic activity (100/1000 mA cm −2 at 1.36/1.49 V vs . RHE, respectively) and a rapid kinetics (19.13 mV dec -1 ). The Ni 3 P on the surface of Ni 3 S 2 can rapidly form highly active γ-NiOOH with low energy consumption, and the formed Ni 3 S 2 @γ-NiOOH accelerates proton-coupled electron transfer (PCET) kinetics through reducing the energy barrier of urea dehydrogenation process, thereby enhancing UOR intrinsic activity. In addition, we also demonstrate a Ni 3 S 2 @Ni 3 P//Ni 3 S 2 @Ni 3 P urea electrolysis device with low voltages of 1.54 and 1.69 V at current densities of 100 and 500 mA cm −2 , respectively. This work proposes an efficient strategy to accelerate the generation of NiOOH on the surface of Ni 3 S 2 during UOR electrocatalysis, revealing the enhanced UOR mechanism of Ni 3 S 2 @Ni 3 P, which can promote the development of urea-assisted hydrogen production .