Bias-Free In Situ H₂O₂ Generation in a Photovoltaic-Photoelectrochemical Tandem Cell for Biocatalytic Oxyfunctionalization

Abstract

Peroxygenases catalyze selective oxyfunctionalization of hydrocarbons with high conversion efficiencies using H 2 O 2 as a key cosubstrate. Here, we report an unbiased photoelectrochemical (PEC) tandem structure consisting of a FeOOH/BiVO 4 photoanode, a Cu(In,Ga)Se 2 solar absorber, and a graphitic carbon nitride/reduced graphene oxide hybrid cathode for light-driven peroxygenase catalysis. Powered by sufficient photovoltage generated by the solar absorber, the PEC platform generates H 2 O 2 in situ through reductive activation of molecular oxygen using water as an electron donor in the absence of external bias. The peroxygenase from Agrocybe aegerita catalyzed the stereoselective hydroxylation of ethylbenzene to (R)-1-phenylethanol with total turnover numbers over 43 300 and high enantioselectivity (ee > 99%) in the unbiased PEC tandem system.

Hemoprotein Catalyzed Oxygenations: P450s, UPOs, and Progress toward Scalable Reactions

“…A photoelectrochemical (PEC) tandem cell structure, consisting of an FeOO/BiVO4 photoanode, a CIGS solar cell, and a CN/rGO cathode, enabled first the oxidation of water at the anode, followed by oxygen reduction at the cathode, to give H 2 O 2 . 122 This was coupled to the Aae UPO-catalyzed hydroxylation of ethylbezene again, giving a TTN of 43 300. A further system employed flavin molecules immobilized on single walled carbon nantotubes which, when irradiated with UV light, stimulated the production of H 2 O 2 from oxygen, enabling Aae UPO-catalyzed hydroxylation of 100 mM ethylbenzene to 17 mM product over 50 h with a TTN of 123 000.…”

Solar‐Assisted eBiorefinery: Photoelectrochemical Pairing of Oxyfunctionalization and Hydrogenation Reactions

“…For example, a PEC system with a dual band gap configuration by coupling a BiVO 4 -based photoanode with a suitable semiconductor (or photovoltaic) could reduce the additional bias to drive biocatalytic reactions by enhanced light harvesting with complementary light absorption. [28] We believe that the scope of our approach can be expanded to other redox enzymatic reactions through the regeneration of nicotinamide cofactors [i.e., NAD(P)H] on the cathode. [29] Numerous oxidoreductases in nature catalyze redox reactions using NAD(P)H as a hydride source.…”

Green Catalysts: Applied and Synthetic Photosynthesis

“…Flavin-based light absorbers have been used to drive the photochemical formation of H2O2 in solution, which in turn serves as co-substrate for the oxyfunctionalization of organic molecules mediated by peroxidase enzymes [151]. Recent work has shown Au-TiO2 nanoparticles [152] and tandem semiconductor-based PEC systems [153] can be used for the photochemical generation of H2O2 from water to drive such enzymatic processes. The photochemical generation of peroxide was similarly coupled to the formation of olefins from the corresponding fatty acid using the enzyme P450 fatty acid decarboxylase [154].…”