Electroreduction-induced in situ surface reconstruction of grain boundary-rich Co3O4 enhancing electrocatalytic ammonia synthesis

Electrocatalysts often undergo reconstruction during the electrochemical process, especially the surface phase. This dynamic evolution makes the relationship between actual microstructure and catalytic activity confusing. Therefore, unraveling this dynamic evolution and further mastering effective methods to provoke advantageous structural emergence is crucial. Herein, we report an electroreduction strategy to stimulate grain boundary-rich Co 3 O 4 nanoneedle going on structure evolution and boosting its catalytic performance toward nitrate reduction reaction (NO 3 RR). Under suitable oxyacid ions solution and reduction potentials, hexagonal Co(OH) 2 nanoplates and oxygen-vacancies (O v ) rich Co 3 O 4-x nanofilm epitaxial growth on Co 3 O 4 nanoneedle. This microstructure evolution enhances the catalytic performance of pristine Co 3 O 4 nanoneedle toward NO 3 RR. Optimal Co 3 O 4-x /Co(OH) 2 @NF electrode achieves a remarkable ammonia Faraday efficiency 93.36 ± 3.66% and a NH 3 yield rate 3.21 ± 0.158 mg h −1  cm −2 at a high potential of 0.05 V vs. RHE. This work presents a novel strategy for engineering high-efficiency electrocatalysts toward NO 3 RR.