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

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 in aqueous solution, the high dissociation energy of N≡N, and the unavoidable competing hydrogen evolution reaction (HER). Herein, a MIL-53(Fe)@TiO catalyst is designed and synthesized for highly efficient eNRR. Relative to simple MIL-53(Fe), MIL-53(Fe)@TiO 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 can maintain a good catalytic activity, while MIL-53(Fe) exhibits a significant decrease in the NH yield rate and FE by 79.8 and 82.3%, respectively. Benefiting from the synergetic effect between TiO and MIL-53(Fe) in the composites, Fe 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 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.