Cathode gas electrode modified with heterogeneous polymeric metal phthalocyanine for achieving high current density for CO2 electroreduction

Achieving high CO2 reduction reaction (CO2RR) current density in traditional H-cells presents significant challenges that require further efforts in both cathodic catalyst and electrolytic cells. This study presents a cathode-gas electrode (CGE) integrated by gas transmission channel and gas diffusion electrode and used in H-cells, named as "CGE/H-cell." Polymerized metal phthalocyanine (M = Co, Fe, Ni)-coated pore-rich nitrogen-doped hollow carbon spheres (NHCSs) were synthesized as cathode catalyst. The optimized polymerized cobalt phthalocyanine (CoPPc)/nitrogen-doped hollow carbon spheres (NHCSs) (COPPc/NHCSs) catalyst shows a moderate d-band center and barrier energy for ∗COOH intermediate formation and ∗CO desorption, thus displays the desirable activity of CO2RR. Owing to breaking the low CO2 solubility limit, CoPPc/NHCSs-based CGE/H-cell achieved a jCO of 206 mA cm−2 and FECO of 85.49% at −1.5 V vs. RHE, and stable operation over 91 h. Using CoPPc/NHCSs as a bifunctional catalyst, the CO2RR coupling with SOR in CGE/H-cell theoretically saves 60% energy consumption and achieves jCO of 121 mA cm−2.