High-Rate and Selective Conversion of Low-Concentration Carbon Dioxide to Carbon Monoxide Using a Carbon Nanotube-Supported Molecular Electrocatalyst

Electrocatalytic CO2 reduction reaction (e-CO2RR), powered by renewable electricity, is a compelling strategy to valorize CO2 into valuable chemicals and fuels. Herein, we report on MWCNT|CuPc-CoPc-modified gas-diffusion electrodes (GDEs) featuring molecular-level dispersion of cobalt phthalocyanine (CoPc) and copper phthalocyanine (CuPc) on the multi-walled carbon nanotube (MWCNT) support. The introduction of CuPc effectively mitigates CoPc aggregation, enabling tunable loading and fractional accessibility of electrochemically active CoPc sites, alongside improved CO2 adsorption capacity. Besides, the synergistic electronic interactions among CoPc, MWCNT, CuPc, and H2Pc, formed in situ via CuPc demetallization during electrolysis, optimized CO2 affinity, as evidenced by density functional theory calculations. With these promising attributes, the MWCNT|CuPc-CoPc-modified GDE with optimized CuPc content exhibits promising e-CO2RR performance across a wide CO2 concentration range (20%–98%). Notably, an efficient single-pass conversion of CO2 to CO is achieved, yielding a high CO yield of 65.7 ± 2.3% and an energy efficiency of 54.8 ± 1.9% using 20% CO2 at an ampere-level current (0.625 A). Furthermore, the developed electrode demonstrated robust stability, maintaining FECO above 80.4% over 72-h electrolysis under a simulated biogas atmosphere (40% CO2/60% CH4). These findings underscore the strong promise of molecularly engineered catalyst systems for efficient and selective CO production from low-concentration CO2 emission sources.