Unbiased Photoelectrode Interfaces for Solar Coupling of Lignin Oxidation with Biocatalytic C═C Bond Hydrogenation

Abstract

The pulp and paper manufacturers generate approximately 50 million metric tons of lignin per annum, most of which has been abandoned or incinerated because of lignin's recalcitrant nature. Here, we report bias-free photoelectrochemical (PEC) oxidation of lignin coupled with asymmetric hydrogenation of CC bonds. The PEC platform consists of a hematite (α-Fe 2 O 3 ) photoanode and a silicon photovoltaic-wired mesoporous indium tin oxide (Si/mesoITO) photocathode. We substantiate a new function of photoelectroactivated α-Fe 2 O 3 to extract electrons from lignin. The extracted electrons are transferred to the Si/mesoITO photocathode for regenerating synthetic nicotinamide cofactor analogues (mNADHs). We demonstrate that the reduction kinetics of mNAD + s depend on their reduction peak potentials. The regenerated mNADHs activate ene-reductases from the old yellow enzyme (OYE) family, which catalyze enantioselective reduction of α,β-unsaturated hydrocarbons. This lignin-fueled biocatalytic PEC system exhibits an excellent OYE's turnover frequency and total turnover number for photobiocatalytic trans-hydrogenation through cofactor regeneration. This work presents the first example of PEC regeneration of mNADHs and opens up a sustainable route for bias-free chemical synthesis using renewable lignin waste as an electron feedstock.

Light-driven biocatalytic oxidation

“…Photoelectrochemical (PEC) systems can overcome this issue because mechanistically (photo)anodes serve as electron acceptors. 127–130 Ottone et al 27 reported ZnO materials for PEC regeneration of NAD + (Fig. 8c).…”

Miscibility Regulation and Thermal Annealing Induced Hierarchical Morphology Enables High‐Efficiency All‐Small‐Molecule Organic Solar Cells Over 17%

“…Achieving an ideal morphology that can maximize charge generation and extraction using suitable materials and treatments is an efficient method to improve device efficiency. [ 30,31 ] Optimization of the active layer morphology needs to achieve suitable domain size, appropriate donor/acceptor (D/A) phase separation, and more reasonable crystallinity, as well as domain purity, for the achievement of efficient excitons dissociation and enhanced charge transport. [ 32,33 ] In this instance, the miscibility of the donor and acceptor is a critical factor in defining the quality of such active layer morphology.…”

Electroenzymatic Reduction of Furfural to Furfuryl Alcohol by an Electron Mediator and Enzyme Orderly Assembled Biocathode

“…To realize effective ex vivo bio-oxidoreductions, recently, the electrochemical NADH regeneration has emerged as an important method showing great potential in enzymatic valorization of biomass-derived molecules, such as lignin, α-ketoglutarate, ketoisophrone, and 2-methylcyclohexenone. − This strategy exhibits remarkable advantages of trace by-product formation, ease of product separation, and the usage of renewable electricity as a power resource. − A common limitation of electroenzymatic catalysis is the slow electron transfer efficiency between NAD + and the electrode, which further leads to low selectivity and poor stability . To overcome the challenges, the assembling of the Rh complex on the working electrodes provides an enlightened avenue in bioconversion .…”