Oxygen Vacancy Engineering of MOF-Derived Zn-Doped Co3O4 Nanopolyhedrons for Enhanced Electrochemical Nitrogen Fixation

Introducing oxygen vacancy (Vo) has been considered as an effective and significant method to accelerate the sluggish electrocatalytic nitrogen reduction reaction (NRR). In this work, a series of bimetallic zeolitic imidazolate frameworks based on ZIF-67 and ZIF-8 with varied ratios of Co/Zn have been applied as precursors to prepare Vo-rich Zn-doped Co3O4 nanopolyhedrons (Zn-Co3O4) by a low-temperature oxidation strategy. Zn-Co3O4 presents an ammonia yield of 22.71 μg h-1 mgcat.-1 with a high faradaic efficiency of 11.9% for NRR under ambient conditions. The remarkable catalytic performances are believed to result from the plentiful Vo as the Lewis acid sites and electron-rich Co sites to promote the adsorption and dissociation of N2 molecules. Remarkably, Zn-Co3O4 also demonstrates a high electrochemical stability. This work presents a guiding method for developing a stable and efficient electrocatalyst for the NRR.