Fig. 5: Electrocatalytic characterization of FdhF_HycB3∆159-184/CNT/GC electrodes.

a Cyclic voltammogram of FdhF_HycB3∆159-184 for electrocatalytic CO₂ reduction; line a (black) was performed in 100% N₂, and line (b) (red) was performed in an atmosphere of CO₂ by bubbling CO₂ with a flow rate of 20 sccm. b Cyclic voltammogram of FdhF_HycB3∆159-184 for electrocatalytic CO₂ reduction at different temperatures. The flow rate of CO₂ was 20 sccm (c) Cyclic voltammogram of FdhF_HycB3∆159-184 electrocatalytic analysis of direct and indirect electron transport, line a (red): FdhF_HycB3∆159-184/CNT/GC electrode was evaluated in 100% N₂; line b (black): the electrode was evaluated in the presence of 0.2 mM methyl viologen (MV) and 100% N₂; line c (blue): the electrode was evaluated in 100% CO₂; line d (green): the electrode was evaluated in the presence of 0.2 mM MV and 100% CO₂. d Linear sweep voltammetry (LSV) at 0 rpm (red), 100 rpm (blue), and 900 rpm (green) in an atmosphere of CO₂. e A potential of −550 mV vs. SHE was applied to FdhF_HycB3∆159-184/CNT/GC for CO₂ reduction in mixed-buffer 0.1 M (Acetate, MES, HEPES, and TAPS), pH 6.0 buffer and NaHCO₃ (0–50 mM) was used as the substrate, 25 °C. f The catalytic currents and substrate concentrations are plotted. The experiments of (a), (b), (c), and (d) were carried out in 0.1 M HEPES, pH 6.2, buffer containing 0.1 M NaCl at 25 °C (excluding temperature optimization experiments), and at a scan rate of 5 mV s⁻¹ (LSV was conducted at a scan rate of 1 mV s⁻¹). HEPES: 4‐(2‐hydroxyethyl)‐1‐piperazineethanesulfonic acid, CNT: Carbon nanotubes. The error bars correspond to the standard deviation of at least three independent measurements, and the center value for the error bars is the average of the three independent measurements. Source data are provided as a Source Data file.