Structure-Activity Relation of Single-Atom Electrocatalysts for CO2 Reduction to CH4
Atomically dispersed single-atom catalysts (SACs) on graphene offer a tunable platform for electrochemical CO2 reduction to CH4, yet the mechanistic coupling between active-site identity and coordination environment remains poorly resolved. This study constructs a structure-activity map for 110 stable SACs with MXnY4−n motifs (X, Y = N, S, P; M = 19 transition metals) using density functional theory and multi-task symbolic regression. The binding strength of the *OCHO intermediate (ΔE*OCHO) is identified as the initial activity descriptor, correlating with the onset potential for CH4. A three-dimensional descriptor comprising valence-electron number and electronegativity of metal and coordinating atoms reproduces ΔE*OCHO and onset potential variations without further DFT calculations. The analysis reveals that coordination environments modulate the d-band center and charge transfer, shifting the rate-determining step from CO2 activation to *CO hydrogenation. This descriptor enables rapid screening of SACs, bypassing computationally expensive DFT workflows. The findings provide a rational basis for designing graphene-supported SACs with enhanced CH4 selectivity and establish a generalizable framework for decoupling active-site and coordination effects in CO2 electrocatalysis.