Carboxyl ligand-regulated Cd metal complexes as efficient catalysts for the electrocatalytic reduction of CO2 to CO

Abstract

Electrocatalytic transformation of carbon dioxide (CO₂) into value-added chemical products represents a promising strategy for addressing today's environmental challenges. Metal complexes show great potential and effectiveness for CO₂ capture and conversion. In this work, three distinct classes of organic ligands, namely, benzoic acid (BA), 1,4-benzenedicarboxylic acid (BDC) and 1,3,5-benzenetricarboxylic acid (BTC), were used to prepare Cd metal complex (Cd-BA, Cd-BDC and Cd-BTC) catalysts. Results showed that the morphologies of Cd-BA, Cd-BDC and Cd-BTC were strip nanosheets, layered nanosheets and irregular nanosheets, respectively. Electrochemical tests showed that the highest Faraday efficiency for CO (FE_CO) was 94.7% when the potential of the Cd-BDC catalyst was −1.4 V versus the reversible hydrogen electrode (vs. RHE). Moreover, across a broad electrochemical potential window from −1.2 V vs. RHE to −1.6 V vs. RHE, FE_CO values were all >90%, and peak current density was −15.49 mA cm⁻² at −1.8 V vs. RHE. Notably, the FE_CO of Cd-BDC remained around 90% after electrolysis for 5 h at a constant voltage of −1.4 V vs. RHE. These findings indicated that the different ligands significantly influenced the morphology control of the Cd metal–organic complex and the electrocatalytic performance for the CO₂ reduction reaction (CO₂RR).