Adjacent Metal Atomic Pairs Within Atomically Dispersed Catalysts for Reaching a Synergistic Electrocatalytic CO₂ Reduction: A Review

In response to the global climate change and energy crisis, electrocatalytic CO₂ reduction reaction (ECR) is regarded as one of the potential ways to simultaneously reach the CO₂ conversion and obtain various value-added products. Currently, several challenges remain for the in-depth understanding of ECR from fundamentals, including ambiguous structure-activity relationships, uncontrollable catalytic selectivity, and complex reaction mechanisms. Compared to traditional metal nanoparticle-based materials, atomically dispersed catalysts (ADCs) have aroused significant interest owing to their maximal atomic utilization and simplified site configuration, offering a superior platform for discussing the structure-activity relationships during ECR. Especially, adjacent metal atomic pairs (AAPs) within ADCs are gradually emphasized as a novel concept to follow various synergistic reaction mechanisms during ECR. Herein, for the first time a broad concept of AAPs and analyzed how AAPs within ADCs reached the synergistic effect during ECR is summarized. In view of the synergistic reaction mechanisms varying on different supports, three types of supports are illustrated (containing graphene model, functional porous frameworks, and metals and oxides), aiming to help scholars with more insights in broadening the feasible synergistic reaction mechanisms on AAPs within ADCs.