A Bidentate Chelation Strategy for Breaking the Thermodynamic Hydrophobicity-Activity Trade-Off to Boost the Electroreduction of CO2 to Formate.

Achieving industrially relevant electrochemical CO2 reduction (CO2RR) to formic acid requires catalyst that simultaneously exhibits high intrinsic activity and surface hydrophobicity. However, high intrinsic activity is considered thermodynamically contradictory on a hydrophobic surface since high hydrophobicity corresponds to low surface energy, thereby leading to low intrinsic activity. Here we overcome this hydrophobicity-activity trade-off via a bidentate chelation strategy that grafts carboxylic acid molecules with tunable alkyl chain lengths on Bi2O2CO3 (XC-BOC, where X denotes the carbon number). The obtained 10C-BOC sustains high hydrophobicity without sacrificing activity. This hydrophobicity-activity balance is achieved by restructuring the interfacial hydrogen-bond (HB) network to suppress the undesired hydrogen evolution reaction (HER) and ensure the timely hydrogenation rate for the key *OCHO intermediate, in conjunction with modulating the Bi site electronic structure via the carboxyl-O/Bi bidentate chelation to guarantee the high intrinsic activity. Consequently, 10C-BOC achieves ampere-level performance with FEHCOO- > 90% from 100-1000 mA cm-2, with an optimal FEHCOO- of 97.7% at 600 mA cm-2 (vs. 83.2% for bare BOC), and maintains FEHCOO- > 93% at 200 mA cm-2 for 200 h. This work offers a general strategy to decouple hydrophobicity from intrinsic activity for advanced CO2RR electrocatalysts.