Electrochemical Ammonia Oxidation Catalyzed by a Ruthenium Complex with a Dangling Sulfonate Group
Huatian Xiong, Jing Yang, Jun Li, Yuanyuan Cai, Feiyang Zhang, Jiayi Chen, Rong‐Zhen Liao, Licheng Sun, Biaobiao Zhang
Abstract
The goal of realizing a direct ammonia fuel cell and using ammonia as a hydrogen carrier motivates the development of electrocatalysts for the oxidation of ammonia to nitrogen. Herein, we report [Ru(bds)(4-methylpyridine) 2 ] ( Ru-bds-Mepy, bds = 2,2′-bipyridine-6,6′-disulfonate) as an efficient electrocatalyst for ammonia oxidation to nitrogen. The decent ammonia oxidation performance of Ru-bds-Mepy was demonstrated by cyclic voltammetry ( k obs of 51.47 s –1 ) and bulk electrolysis (turnover number of 390). The hydrogen bond interaction between the coordination ammonia and the dangling sulfonate group was observed in the crystal structure and further demonstrated by density functional theory (DFT) calculations. Kinetic studies indicate that Ru-bds-Mepy exhibits first-order kinetics with respect to both catalyst and ammonia concentration. Then, DFT calculations suggest the potential of N–N bond formation via the nucleophilic attack of NH 3 on the Ru VI nitride complex in a barrierless and rapid way. This study contributes an efficient ammonia oxidation catalyst with a record-high turnover number.