Structure-Activity Relation of Single-Atom Electrocatalysts for CO2 Reduction to CH4

• • The binding energy of *OCHO (ΔE*OCHO) serves as a single activity indicator for CH4 production across 110 SACs, with a mean absolute deviation of 0.12 eV from DFT benchmarks, enabling rapid screening without full reaction pathway calculations. • • A three-dimensional descriptor (valence-electron number and electronegativity of metal and coordinating atoms) predicts onset potentials for CH4 with R² = 0.89, reducing computational cost by >90% compared to explicit DFT for each candidate. • • Coordination environments (N, S, P) shift the d-band center of metal sites by up to 1.2 eV, altering the rate-determining step from CO2 activation to *CO hydrogenation, which directly impacts CH4 selectivity over CO. • • The identified descriptor enables high-throughput screening of 19 transition metals across 6 coordination motifs, identifying Cu-N4 and Fe-N3S1 as top candidates with onset potentials below −0.6 V vs. RHE, relevant for industrial-scale CO2 electrolyzers operating at 100–200 mA/cm².