Direct detection of a single [4Fe‐4S] cluster in a tungsten‐containing enzyme: Electrochemical conversion of CO₂ into formate by formate dehydrogenase

Abstract

The conversion of CO2 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 CO2 and formate in the presence of substrates. The turnover frequency of electrochemical CO2 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 CO2 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.

Bioelectrocatalytic Synthesis: Concepts and Applications

“…Looking toward efficient CO 2 reduction, the Zhang group has utilized the same ClFDH enzyme via direct electron transfer. [111] These W-containing enzymes display non-NADH dependence due to their [4FeÀ 4S] clusters at the surface of the enzyme; this structural feature allows direct electron transfer from the electrode, enabling a direct interrogation of the kinetics and thermodynamics of the transformation. After the application of À 0.6 V (vs. SHE) for 2 hr, the faradaic efficiency of the reaction was measured as 99.3 %, a new benchmark for an electroenzymatic CO 2 reduction to formate.…”

Electrocatalysis of CO2 Reduction by Immobilized Formate Dehydrogenase without a Metal Redox Center

“…20 This type of FDH could achieve direct electron transfer (DET) from the electrode surface to CO 2 without the help of a cofactor. 21 Metal-dependent FDH are present in anaerobic prokaryotes and perform with high efficiency for the CO 2 RR with high turnover frequency. 22 However, their extraction is time-and cost-demanding.…”

“…The second type of FDH enzyme contains metal atoms, Mo or W, in the enzyme’s active center (metal-dependent FDH) . This type of FDH could achieve direct electron transfer (DET) from the electrode surface to CO 2 without the help of a cofactor . Metal-dependent FDH are present in anaerobic prokaryotes and perform with high efficiency for the CO 2 RR with high turnover frequency .…”