Engineered d-p orbital hybridization unlocks dilute CO2 electrolysis to byproduct-free CH4-rich syngas

Electrochemical CO2 methanation from flue gas offers a promising approach for upgrading point-source emissions and synthesizing energy-dense CH4. However, it remains challenging for both the direct utilization of dilute upstream and the extra downstream separation of complex byproducts. Here, we develop a gaseous byproduct-free system with an inlet of flue gas and an outlet of CH4-rich syngas for metallurgy and energy fields, wherein rationally designed Sn-based electrocatalysts are integrated with the direct electrolysis of bicarbonate-rich capture media, facilitated by engineered electrolyte distributors within scale-up flow cells. Specifically, guided by computational screening of atomic configurations, we engineer a high-density ensemble of sub-nanoscale SnNi clusters (7~8 Å) on a Ni-N-C architecture. The atomic arrangement and local coordination are resolved via operando synchrotron X-ray pair distribution function analysis. Consequently, near-zero multi-carbon byproducts are achieved by steering enhanced d-p orbital hybridization of Ni-CHO with a partial current density of CH4 over 1000 mA/cm2. With the simulated flue gas inlet, approximately 1500 L CH4-rich syngas is collected in around five days with flow cells. Electrochemical conversion of CO2 from dilute flue gas into methane remains limited by complex byproducts. Here, the authors integrate a tin-nickel catalyst into flow cells to convert captured CO2 directly into methane-rich syngas with near-zero multicarbon byproducts.