Electrocatalytic Interconversions of CO<sub>2</sub> and Formate on a Versatile Iron-Thiolate Platform
Yongxian Li, Jiayi Chen, Xinchao Zhang, Zhiqiang Peng, Qiyi Miao, Wang Chen, Fei Xie, Rong‐Zhen Liao, Shengfa Ye, Chen‐Ho Tung, Wenguang Wang
Abstract
Exploring bidirectional CO 2 /HCO 2 – catalysis holds significant potential in constructing integrated (photo)electrochemical formate fuel cells for energy storage and applications. Herein, we report selective CO 2 /HCO 2 – electrochemical interconversion by exploiting the flexible coordination modes and rich redox properties of a versatile iron-thiolate platform, Cp*Fe(II)L (L = 1,2-Ph 2 PC 6 H 4 S – ). Upon oxidation, this iron complex undergoes formate binding to generate a diferric formate complex, [(L – ) 2 Fe(III)(μ-HCO 2 )Fe(III)] +, which exhibits remarkable electrocatalytic performance for the HCO 2 – -to-CO 2 transformation with a maximum turnover frequency (TOF max ) ∼10 3 s –1 and a Faraday efficiency (FE) ∼92(±4)%. Conversely, this iron system also allows for reduction at −1.85 V (vs Fc +/0 ) and exhibits an impressive FE ∼93 (±3)% for the CO 2 -to-HCO 2 – conversion. Mechanism studies revealed that the HCO 2 – -to-CO 2 electrocatalysis passes through dicationic [(L 2 ) −• Fe(III)(μ-HCO 2 )Fe(III)] 2+ generated by unconventional oxidation of the diferric formate species taking place at ligand L, while the CO 2 -to-HCO 2 – reduction involves a critical intermediate of [Fe(II)-H] − that was independently synthesized and structurally characterized.