FeN 4 -Embedded Graphene as a Highly Sensitive and Selective Single-Atom Sensor for Reaction Intermediates of Electrochemical CO 2 Reduction.

Exploring effective ways to detect intermediates during the electrochemical CO 2 reduction reaction (CO 2 RR) process is pivotal for understanding reaction pathways and underlying mechanisms. Recently, two-dimensional FeN 4 -embedded graphene has received increasing attention as a promising catalyst for CO 2 RR. Here, by means of density functional theory computations combined with the non-equilibrium Green's function (NEGF) method, we proposed a detection device to evaluate the performance of FeN 4 -embedded graphene in intermediates detection during the CO 2 RR process. Our results reveal that the four key intermediates, including *COOH, *OCHO, *CHO, and *COH, can be chemisorbed on FeN 4 -embedded graphene with high adsorption energies and appropriate charge transfer. The computed current-voltage ( I - V ) characteristics and transmission spectra suggest that the adsorption of these intermediates induces significant type-dependent changes in currents and transmission coefficients of FeN 4 -embedded graphene. Remarkably, the FeN 4 -embedded graphene is more sensitive to *COOH and *COH than to *OCHO and *CHO within the entire bias window. Consequently, our theoretical study indicates that the FeN 4 -embedded graphene can effectively detect the key intermediates during the CO 2 RR process, providing a practical scheme for identifying catalytic reaction pathways and elucidating underlying reaction mechanisms.