A Unique Gas-Migration, Trapping, and Emitting Strategy for High-Loading Single Atomic Cd Sites for Carbon Dioxide Electroreduction.

Single-atom catalysts (SACs) exhibit great potential in heterogeneous catalysis. However, the achievement of obtaining high-loading SACs remains a bottleneck. Herein, we first demonstrate a unique gas-migration, trapping, and emitting strategy for building a kind of Cd-based SAC for CO2 reduction (CO2RR). The gas-migration and trapping processes (≤750 °C) endows the material with an ultrahigh Cd loading amount of 30.3 wt %, while the emitting process can facilely modulate the loading amount from 30.3 to 1.4 wt %. For the CO2RR, the Cd-NC SACs with a loading amount of 18.4 wt % exhibits the maximum Faraday efficiency of 91.4% for CO at -0.728 V. The operando infrared spectroscopy studies prove the presence of main intermediates *COO-, *COOH, and *CO on Cd-NC-5M SACs during the catalytic process, indicating that the CO2RR follows the proton-decoupled electron-transfer mechanism. Density functional theory simulations reveal that the Cd-N4 structure reduces the Gibbs free energy of the rate-determining step (the hydrogenation step of *COOH).