Efficiency enhancement of nitrate electroreduction to ammonia by introducing Co(OH)2 nanosheets on Cu2O microsphere: Increase supply and reduce resistance

Electrocatalytic NO3− reduction reaction (NO3RR) has attracted much attention as a promising NH3 synthesis pathway, and Cu-based catalysts have been proven to lead to advantages in nitrate reduction. However, the active hydrogen (H*) produced by the Cu-based catalyst is insufficient to satisfy the hydrogenation process of the NO3RR intermediate, resulting in a large generation of NO2−. In this paper, the Co(OH)2/Cu2O heterojunction was constructed to improve the kinetics of H2O dissociation to generate H* and Co(OH)2/Cu2O (5.87 %) showed lower faradaic efficiency (FE) of NO2− than Cu2O (50.95 %). Mechanistic studies reveal that the introduction of Co(OH)2 can help Cu2O lower the energy barrier of H2O dissociation, greatly boosting the supply of active hydrogen (H*). Not only that, but the reaction energy barriers of *NO to *NOH can be greatly reduced. The final twofold reason works together to greatly improve the efficiency of hydrogenation of NO2−, largely solving the problem of FE reduction due to the delayed consumption of NO2−, thus realizing improved performance.