Efficient photoelectrocatalytic CO2 reduction to CH3OH via porous g-C3N4 nanosheets modified with cobalt phthalocyanine in ionic liquids

Abstract

Photocatalytic CO₂ reduction into fuels is desirable; however, realizing efficient C_nH_2n+1OH (n = 1, 2) synthesis that involves electron-coupled proton transfer alongside C–C bond formation remains a challenge. Here, we demonstrated a photoelectrocatalytic (PEC) CO₂ reduction strategy to generate CH₃OH and CH₃CH₂OH on cobalt phthalocyanine/g-C₃N₄ (CoPc/CN) in ionic liquids (ILs). In situ infrared spectroscopy indicated that *HCOO was a key intermediate for the evolution of CH₃OH, and density functional theory (DFT) revealed that the Gibbs energy of C–C coupling dropped significantly from 4.94 to 2.21 eV in the ILs electrolyte. The carrier separation efficiency was enhanced in [BMMIm]Br electrolyte, in which photocurrent was 9-fold higher than that in KHCO₃. This strategy achieved record-high CH₃OH and CH₃CH₂OH generation abilities (6465.9 and 218.6 μM cm⁻² h⁻¹), which were 60.7- and 17.8-fold higher than those in KHCO₃, respectively. Therefore, this work develops a PEC strategy to obtain excellent CH₃OH yield, and provides new insight into the C–C coupling mechanism in IL-assisted CO₂ reduction.