Photoelectrochemical CO₂ Reduction to Formate with the Sacrificial Reagent Free System of Semiconductor Photocatalysts and Formate Dehydrogenase

Abstract

Efficient sacrificial reagent free (and no external bias) photoelectrochemical CO 2 reduction to formate with a hybrid system consisting of semiconductor-based photocatalytic TiO 2 nanoparticles, methylviologen (MV) as an electron carrier, and biocatalytic formate dehydrogenase (FDH) was investigated. To develop the sacrificial reagent free photoelectrochemical cell for the CO 2 reduction to formate, the photoanode based on TiO 2 film and cathode based on the carbon fabric paper (CFP) were separated into two compartments using a protonpermeable Nafion film to prevent gas diffusion. When the anode was irradiated with Xenon lamp (> 300 nm), MV reduction and CO 2 reduction to formate with FDH on the cathode side proceeded in this system. For MV reduction with photoelectrochemical cell, MV was reduced using TiO 2 film at each pH (6, 7 and 8) without bias, the reduction of MV did not progressed at pH 6. In contrast, MV reduction was progressed at pH 7 or 8. For CO 2 reduction to formate in the presence FDH on the cathode side with photoelectrochemical cell, the rate of formate production was estimated to be 31.9 nmol h À 1 at pH 8 under continuous irradiation without bias. Moreover, the rates of formate production at pH 7 and 8 were estimated to be 56.5 and 168.8 nmol h À 1 , respectively under continuous irradiation with bias (0.4 V vs. cathode). By using this system, we have succeeded in constructing CO 2 reduction to formate using water as an electron donor, which does not require a sacrificial reagent.[a] T. Figure 1. Formic acid-CO 2 conversion catalyzed with FDH in the presence of natural co-enzyme NAD + /NADH redox coupling.

Visible‐Light Driven CO2 Reduction to Formate with Electron Mediated Nicotinamide‐Modified Viologen in the System of Water‐Soluble Zinc Porphyrin and Formate Dehydrogenase

“…On the other hand, we are constructing a light driven CO 2 reduction to formate system using the semiconductor photocatalyst TiO 2 as a photosensitizer and MV and CbFDH. In this system, formate was stably produced even after continuous irradiation for 16‐h, suggesting that the catalytic activity of CbFDH is stable with respect to the irradiation [26] . It was concluded that while semiconductor photocatalysts are stable to irradiation, there is a problem with the photodurability of metallo‐coordination complex‐based photosensitizers such as water‐soluble zinc porphyrins.…”

“…In contrast, the light driven CO 2 reduction to formate systems with the coupling the photoreduction of various 4,4 ′ ‐ or 2,2 ′ ‐bipyridinium salts (4,4 ′ ‐ or 2,2 ′ ‐BPs) with water‐soluble ruthenium polypyridyl coordination complexes, water soluble zinc porphyrins, Mg chlorophyll‐ a or photocatalyst based on the semiconductor such as TiO 2 and CbFDH have been reported as shown in Figure 3 [13–26] …”

Research Progress in Conversion of CO2 to Valuable Fuels

“…Therefore, the overall yield of formate would be preserved without loss from reoxidation [ 150 ]. Ishibashi et al [ 151 ] used methyl viologen (MV 2+ ) instead of NADH. A photoelectrochemical system was composed of TiO 2 nanoparticles as photocatalyst, MV 2+ as electron carrier, and FDH as biocatalyst, in which CO 2 was successfully reduced to formic acid without sacrificing reagent, external bias, and NADH.…”

Visible-light-driven CO2reduction to formate with a system of water-soluble zinc porphyrin and formate dehydrogenase in ionic liquid/aqueous media

“…We also previously reported the visible-light-driven CO 2 reduction to formate with the system consisting of various 2,2 0 -11 or 4,4 0 -BPs, 12,14 CbFDH and water-soluble zinc porphyrin. NAD + cannot be directly reduced to NADH in the photoredox system using ZnTPPS or ruthenium(II) coordination compounds.…”

“…Among these technologies, a system of light-driven CO 2 reduction to CO, formate or methanol, consisting of a photosensitizer, an electron mediator and a biocatalyst, was developed. [2][3][4][5][6][7][8][9][10][11][12][13][14] Among these biocatalysts, formate dehydrogenase (FDH) catalyzes the CO 2 reduction to formate in the presence of a co-enzyme such as NADH, and single-electron reduced 4,4 0 -or 2,2 0 -bipyridinium salts (BP). Thus, visible-light-driven CO 2 reduction to formate system is developed with the photoredox system of a photosensitizer, an electron mediator and FDH.…”