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

Jinhyun Kim, Yunna Um, Seunghyun Han, Thomas Hilberath, Yong Hwan Kim, Frank Hollmann, Chan Beum Park*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


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-Fe2O3) photoanode and a silicon photovoltaic-wired mesoporous indium tin oxide (Si/mesoITO) photocathode. We substantiate a new function of photoelectroactivated α-Fe2O3 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.

Original languageEnglish
Pages (from-to)11465-11473
Number of pages9
JournalACS Applied Materials and Interfaces
Issue number9
Publication statusPublished - 2022

Bibliographical note

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.


  • biocatalysis
  • hematite
  • lignin
  • photoelectrocatalysis
  • trans-hydrogenation


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