No 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.

(Photo)­Electrochemical CO2 transformation to produce valuable chemicals or biofuels is one of the essential technologies for the carbon-neutral economy to store clean and renewable energy in chemical bonds. Herein, we show an efficient photocatalytic assembly formed by coupling formate dehydrogenase from Clostridium ljungdahliia (ClFDH), silver nanoclusters (AgNCs), TiO2, and graphitic carbon nitride (g-C3N4). The resulting integrated system is stable and can convert CO2 into formate with a turnover frequency of 1 s–1 and a turnover number of over 10,000 in 4 h. We highlight the key roles AgNCs have played to achieve such durability and high efficiency, which include (1) increasing the overall loading of biocatalysts and optimizing the orientation of enzyme molecules upon semiconductors by the Ag–cysteine interaction; (2) as the electron mediator, facilitating the interfacial electron transfer; and (3) scavenging the enzyme-deactivating reactive oxygen species. Our results provide a paradigm of selective CO2-capturing reaction under ambient conditions.