Interfacial Engineering Boosting the Activity and Stability of MIL-53(Fe) toward Electrocatalytic Nitrogen Reduction

Abstract

The electrochemical nitrogen reduction reaction (eNRR) has emerged as a promising strategy for green ammonia synthesis. However, it suffers unsatisfactory reaction performance owing to the low aqueous solubility of N 2 in aqueous solution, the high dissociation energy of N�N, and the unavoidable competing hydrogen evolution reaction (HER). Herein, a MIL-53(Fe)@ TiO 2 catalyst is designed and synthesized for highly efficient eNRR. Relative to simple MIL-53(Fe), MIL-53(Fe)@TiO 2 achieves a 2-fold enhancement in the Faradaic efficiency (FE) with an improved ammonia yield rate by 76.5% at −0.1 V versus reversible hydrogen electrode (RHE). After four cycles of electrocatalysis, MIL-53(Fe)@TiO 2 can maintain a good catalytic activity, while MIL-53(Fe) exhibits a significant decrease in the NH 3 yield rate and FE by 79.8 and 82.3%, respectively. Benefiting from the synergetic effect between TiO 2 and MIL-53(Fe) in the composites, Fe 3+ ions can be greatly stabilized in MIL-53(Fe) during the eNRR process, which greatly hinders the catalyst deactivation caused by the electrochemical reduction of Fe 3+ ions. Further, the charge transfer ability in the interface of composites can be improved, and thus, the eNRR activity is significantly boosted. These findings provide a promising insight into the preparation of efficient composite electrocatalysts.