Direct detection of a single [4Fe‐4S] cluster in a tungsten‐containing enzyme: Electrochemical conversion of CO<sub>2</sub> into formate by formate dehydrogenase
Wenjin Li, Yanxin Gao, Xuan Sun, Lei Wan, Haishuo Ji, Hang Luo, Yao Tian, Hao Song, Geng Wu, Liyun Zhang
Abstract
Abstract The conversion of CO 2 into fuels and valuable chemicals is one of the central topics to combat climate change and meet the growing demand for renewable energy. Herein, we show that the formate dehydrogenase from Clostridium ljungdahlii (ClFDH) adsorbed on electrodes displays clear characteristic voltammetric signals that can be assigned to the reduction and oxidation potential of the [4Fe‐4S] 2+/+ cluster under nonturnover conditions. Upon adding substrates, the signals transform into a specific redox center that engages in catalytic electron transport. ClFDH catalyzes rapid and efficient reversible interconversion between CO 2 and formate in the presence of substrates. The turnover frequency of electrochemical CO 2 reduction is determined as 1210 s −1 at 25 °C and pH 7.0, which can be further enhanced up to 1786 s −1 at 50°C. The Faradaic efficiency at −0.6 V (vs. standard hydrogen electrode) is recorded as 99.3% in a 2‐h reaction. Inhibition experiments and theoretical modeling disclose interesting pathways for CO 2 entry, formate exit, and OCN − competition, suggesting an oxidation‐state‐dependent binding mechanism of catalysis. Our results provide a different perspective for understanding the catalytic mechanism of FDH and original insights into the design of synthetic catalysts.