Elaborated Built-In Electric Field in Mn/C60 Heterojunction Promotes Electrocatalytic Nitrogen Reduction to Ammonia

Abstract

Electrochemical nitrogen reduction reaction (NRR) has been regarded as a green and promising alternative to the traditional Haber–Bosch process. However, the high bond energy (940.95 kJ mol-1) of the N≡N triple bond hinders the adsorption and activation of N₂ molecules, which is a critical factor restricting the catalytic performance of catalysts and its large-scale applications. Herein, Mn/C60 heterostructure is constructed via a simple grinding and calcination process and achieve an extraordinary Faradaic efficiency of 42.18% and a NH3 yield rate of 14.52 μg h−1 mgcat−1 at −0.4 V vs. RHE in 0.08 M Na2HPO4. Our experimental and theoretical results solidly confirm that the spontaneous charge transfer at the Mn/C60 heterointerface promote the formation of built-in electric field, which facilitate the electron transfer from Mn towards C60 and fabricate localized electrophilic and nucleophilic regions. The formation of the space-charge region effectively optimized the adsorption energy of forming key intermediate *NH-*NH2 and also reduced the free energy barrier for the hydrogenation step of *NH-*NH to *NH-*NH2. Furthermore, the calculated lower limiting potential (UL(NRR)) in Mn/C60 relative to HER (UL(HER)) demonstrating the enhanced selectivity toward NRR. This work provided new insights into enhancing the activity and performance of electrocatalysts for NRR by constructing heterojunctions to improve nitrogen adsorption.