Defect engineering in earth-abundant electrocatalysts for CO2 and N2 reduction

The electrocatalytic CO2 reduction reaction (CRR) and N-2 reduction reaction (NRR), which convert inert small molecules into high-value products under mild conditions, have received much research attention. Defect engineering is an important strategy for modulating the electronic properties of electrocatalysts, which may endow unexpected physical and chemical properties to break the intrinsic bottleneck and, therefore, boost the electrocatalytic performance. To date, various defective nanomaterials (such as nanocarbon and transition metal compounds) have been synthesized that display great potential for the CRR and NRR. Therefore, a deep understanding of the influence of defects on the catalytic activity is urgently needed. In this review, the type, regulation strategy, fine defect characterization methods, and their application in the electrocatalytic CRR and NRR are discussed and summarized. Furthermore, the major challenges, opportunities, and future development direction of defect engineering in CRR and NRR catalysts are proposed. This review aims to provide a reference for the proof-of-concept design of highly active CRR and NRR electrocatalysts.