Harvesting photosynthetic reducing power stored
8 affiliations
- 1Department of Chemical and Biological Engineering
- 2Korea University of Technology
- 3Department of Intelligent Energy and Industry
- 4Chung–Ang University
- 5School of Chemistry
- 6UNSW Sydney
- 7Department of Chemistry
- 8Ajou University
Abstract
Photosynthesis stores captured light energy as chemical reducing power in NADPH.However, harnessing this stored energy in artificial bioelectrodes has remained difficult.Here we use a Cu-deposited TiO₂ nanotube junction to couple photosynthetic NADPH generation and re-oxidation within a shared chloroplast-derived interface.The scaffold reorganizes isolated spinach chloroplasts into a thin layer, bringing the stromal NADPHproducing region near nanoscale Cu charge-extraction sites.Sequential inhibition across the native electron-transport chain, combined with direct NADPH electrochemistry, assigns approximately 87% of the bio-derived photocurrent to NADPH re-oxidation.Under visible illumination, the Cu-containing junction delivers a photocurrent density of 11.8 μA cm -2 at 0 V versus Ag/AgCl, compared with 2.7 μA cm -2 for its Cu-free counterpart; the former is among the highest reported for mediator-free photosynthetic biohybrid electrodes.The open-circuit voltage changes only modestly, from 0.85 to 0.90 V, consistent with a role for Cu in interfacial charge extraction.Electronic-structure calculations show nearly spin-symmetric nicotinamide-projected states on Cu, in contrast to the nicotinamide-centred spin polarization that develops on oxide surfaces along the reaction pathway.Together, these findings provide a framework for discussing how chloroplastbased biohybrid electrodes can use light energy directly for chemical energy storage in NADPH and subsequently recover the stored reducing power as electrical output.The ability of photosynthesis to convert transient light into chemical energy has long motivated artificial approaches to solar energy conversion 1 .Within the thylakoid membrane, the photosynthetic apparatus integrates light absorption, charge separation, electron transport, and chemical energy storage under ambient aqueous conditions 2,3 .A central challenge in this process is to stabilize absorbed energy before it is lost through rapid excited-state relaxation.The thylakoid membrane addresses this problem through highly efficient charge separation at photosystem (PS) II 4 .The resulting electrons then move through an ordered transport chain.Water oxidation at PS II supplies electrons that pass through the plastoquinone pool, cytochrome b6f, and PS I, ultimately reducing NADP + to NADPH on the stromal side [5][6][7] .At this point, the energy initially captured from light is stored as chemical reducing power in a diffusible cofactor 8,9 .Chloroplasts preserve this sequence within the native membrane architecture, making them attractive components for biohybrid photoelectrochemical systems.Previous efforts to extract electrical current from photosynthetic assemblies have used systems ranging from isolated reaction-center proteins to intact thylakoids, whole cells, and organelles 10,11 .Most of these approaches treat the biological component as a light-driven electron source, with electrons extracted from intermediate carriers in the photosynthetic chain through redox mediators [12][13][14] or direct contact with an electrode [15][16][17] .This framework does not fully reflect how photosynthesis stores energy.In nature, linear photosynthetic electron transport delivers reducing equivalents to NADPH as a terminal soluble reductant.Intercepting electrons upstream of this step therefore uses photosynthesis as a source of photogenerated charge.Such approaches leave the reducing power stored in NADPH unused and do not separate light-driven charge generation from its subsequent electrochemical use.
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BibTeX
@misc{seo2026harvesting,
title = {{Harvesting photosynthetic reducing power stored}},
author = {Abraham Seo and Ji Hun Yeom and Jeongyeon Oh and Jua Jung and Tae Yong Kim and Seyoung Choi and Yujin Lee and Suyeon Chae and Junha Lim and Seohyeon Jang and Seoyeon Jeong and Yeeun Bae and Sanghyuk Lee and Sungju Yu and Inho Nam and Soomin Park},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010542/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010542/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Harvesting photosynthetic reducing power stored
AU - Abraham Seo
AU - Ji Hun Yeom
AU - Jeongyeon Oh
AU - Jua Jung
AU - Tae Yong Kim
AU - Seyoung Choi
AU - Yujin Lee
AU - Suyeon Chae
AU - Junha Lim
AU - Seohyeon Jang
AU - Seoyeon Jeong
AU - Yeeun Bae
AU - Sanghyuk Lee
AU - Sungju Yu
AU - Inho Nam
AU - Soomin Park
PY - 2026
DA - 2026/10/15
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010542/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010542/v1
AB - Photosynthesis stores captured light energy as chemical reducing power in NADPH.However, harnessing this stored energy in artificial bioelectrodes has remained difficult.Here we use a Cu-deposited TiO₂ nanotube junction to couple photosynthetic NADPH generation and re-oxidation within a shared chloroplast-derived interface.The scaffold reorganizes isolated spinach chloroplasts into a thin layer, bringing the stromal NADPHproducing region near nanoscale Cu charge-extraction sites.Sequential inhibition across the native electron-transport chain, combined with direct NADPH electrochemistry, assigns approximately 87% of the bio-derived photocurrent to NADPH re-oxidation.Under visible illumination, the Cu-containing junction delivers a photocurrent density of 11.8 μA cm -2 at 0 V versus Ag/AgCl, compared with 2.7 μA cm -2 for its Cu-free counterpart; the former is among the highest reported for mediator-free photosynthetic biohybrid electrodes.The open-circuit voltage changes only modestly, from 0.85 to 0.90 V, consistent with a role for Cu in interfacial charge extraction.Electronic-structure calculations show nearly spin-symmetric nicotinamide-projected states on Cu, in contrast to the nicotinamide-centred spin polarization that develops on oxide surfaces along the reaction pathway.Together, these findings provide a framework for discussing how chloroplastbased biohybrid electrodes can use light energy directly for chemical energy storage in NADPH and subsequently recover the stored reducing power as electrical output.The ability of photosynthesis to convert transient light into chemical energy has long motivated artificial approaches to solar energy conversion 1 .Within the thylakoid membrane, the photosynthetic apparatus integrates light absorption, charge separation, electron transport, and chemical energy storage under ambient aqueous conditions 2,3 .A central challenge in this process is to stabilize absorbed energy before it is lost through rapid excited-state relaxation.The thylakoid membrane addresses this problem through highly efficient charge separation at photosystem (PS) II 4 .The resulting electrons then move through an ordered transport chain.Water oxidation at PS II supplies electrons that pass through the plastoquinone pool, cytochrome b6f, and PS I, ultimately reducing NADP + to NADPH on the stromal side [5][6][7] .At this point, the energy initially captured from light is stored as chemical reducing power in a diffusible cofactor 8,9 .Chloroplasts preserve this sequence within the native membrane architecture, making them attractive components for biohybrid photoelectrochemical systems.Previous efforts to extract electrical current from photosynthetic assemblies have used systems ranging from isolated reaction-center proteins to intact thylakoids, whole cells, and organelles 10,11 .Most of these approaches treat the biological component as a light-driven electron source, with electrons extracted from intermediate carriers in the photosynthetic chain through redox mediators [12][13][14] or direct contact with an electrode [15][16][17] .This framework does not fully reflect how photosynthesis stores energy.In nature, linear photosynthetic electron transport delivers reducing equivalents to NADPH as a terminal soluble reductant.Intercepting electrons upstream of this step therefore uses photosynthesis as a source of photogenerated charge.Such approaches leave the reducing power stored in NADPH unused and do not separate light-driven charge generation from its subsequent electrochemical use.
ER -