Atomic Tuning of Single-Atom Fe-N-C Catalysts with Phosphorus for Robust Electrochemical CO 2 Reduction.

The electrochemical reduction of CO 2 to produce carbon-based fuels and chemicals possesses huge potentials to alleviate current environmental problems. However, it is confronted by great challenges in the design of active electrocatalysts with low overpotentials and high product selectivity. Here we report the atomic tuning of a single-Fe-atom catalyst with phosphorus (Fe-N/P-C) on commercial carbon black as a robust electrocatalyst for CO 2 reduction. The Fe-N/P-C catalyst exhibits impressive performance in the electrochemical reduction of CO 2 to CO, with a high Faradaic efficiency of 98% and a high mass-normalized turnover frequency of 508.8 h -1 at a low overpotential of 0.34 V. On the basis of ex-situ X-ray absorption spectroscopy measurements and DFT calculations, we reveal that the tuning of P in single-Fe-atom catalysts reduces the oxidation state of the Fe center and decreases the free-energy barrier of *CO intermediate formation, consequently maintaining the electrocatalytic activity and stability of single-Fe-atom catalysts.