Engineering Ag-Nx Single-Atom Sites on Porous Concave N-Doped Carbon for Boosting CO2 Electroreduction.

The electrochemical CO2 reduction reaction (CO2RR) offers an environmentally benign pathway for renewable energy conversion and further regulation of the environmental CO2 concentration to achieve carbon cycling. However, developing desired electrocatalysts with high CO Faradaic efficiency (FECO) at an ultralow overpotential remains a grand challenge. Herein, we report an effective CO2RR electrocatalyst that features Ag single-atom coordinated with three nitrogen atoms (Ag1-N3) anchored on porous concave N-doped carbon (Ag1-N3/PCNC), which is identified by X-ray absorption spectroscopy. Ag1-N3/PCNC shows a low CO2RR onset potential of -0.24 V, high maximum FECO of 95% at -0.37 V, and high CO partial current density of 7.6 mA cm-2 at -0.55 V, exceeding most of the previous Ag electrocatalysts. The in situ infrared absorption spectra technique proves that Ag1-N3 single-atom sites have sole linear-adsorbed CO and can easily desorb *CO species to achieve the highest CO selectivity in comparison with the corresponding counterparts. This work provides significant inspiration on boosting CO2RR by tuning the active center at an atomic level to achieve a specific absorption with an intermediate.