Organic Molecule Functionalization Enables Selective Electrochemical Reduction of Dilute CO2 Feedstock

Abstract The electrochemical conversion of low‐concentration CO 2 feedstock to value‐added chemicals and fuels is a promising pathway for achieving direct valorization of waste gas streams. However, this is challenging due to significant competition from the hydrogen evolution reaction (HER) and lowered CO 2 reduction (CO 2 R) kinetics as compared to systems that employ pure CO 2 . Here we show that terephthalic acid (TPA) functionalization can boost selectivity towards CO 2 R and suppress HER over a range of catalysts including Bi, Cu and Zn. For instance, TPA functionalized Bi attained a formate Faradaic efficiency (FE HCOO‐ ) of 96.3 % at 300 mA cm −2 with pure CO 2 feedstock. Density functional theory simulations indicate that this is because TPA functionalization modulates the binding energies of the key reaction intermediates *OCHO and *H. With low‐concentration feedstock (15 % CO 2 ) at 100 mA cm −2 , we achieved a high FE HCOO‐ of 85.8 %, which was double that of an unmodified Bi catalyst. Using an electrolyzer with a porous solid electrolyte layer, we successfully showcase 30 h of continuous high‐purity formic acid production with a 5 % CO 2 feed. Taken together, our findings demonstrate that molecular tuning of a catalyst can be an effective strategy for enabling selective CO 2 R using low‐concentration feedstock.