{
  "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.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Chemical and Biological Engineering",
    "Korea University of Technology",
    "Department of Intelligent Energy and Industry",
    "Chung–Ang University",
    "School of Chemistry",
    "UNSW Sydney",
    "Department of Chemistry",
    "Ajou University"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 16,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Abraham Seo"
    },
    {
      "affs": [
        2,
        3
      ],
      "name": "Ji Hun Yeom"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Jeongyeon Oh"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Jua Jung"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Tae Yong Kim"
    },
    {
      "affs": [
        2,
        3,
        4,
        5
      ],
      "name": "Seyoung Choi"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Yujin Lee"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Suyeon Chae"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Junha Lim"
    },
    {
      "affs": [
        2,
        3
      ],
      "name": "Seohyeon Jang"
    },
    {
      "affs": [
        2,
        3
      ],
      "name": "Seoyeon Jeong"
    },
    {
      "affs": [
        2,
        3
      ],
      "name": "Yeeun Bae"
    },
    {
      "affs": [
        6,
        7
      ],
      "name": "Sanghyuk Lee"
    },
    {
      "affs": [
        6,
        7
      ],
      "name": "Sungju Yu"
    },
    {
      "affs": [
        2,
        3
      ],
      "name": "Inho Nam"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Soomin Park",
      "orcid": "0000-0001-6787-2098"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/b1w3cnf2cas6f.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15010542/v1",
  "fulltext_url": null,
  "id": "b1w3cnf2cas6f",
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  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010542/v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1312|Photosynthetic Processes and Mechanisms"
    ]
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  "openalex": "W7222079702",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15010542/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-15",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/b1w3cnf2cas6f.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:24Z",
      "native_id": "10.26434/chemrxiv.15010542",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010542/v1"
    }
  ],
  "subjects": [
    {
      "field": "biochemistry",
      "origin": "openalex:1312|Photosynthetic Processes and Mechanisms",
      "subfield": "molecular-biology"
    }
  ],
  "title": "Harvesting photosynthetic reducing power stored",
  "title_text": "Harvesting photosynthetic reducing power stored",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:24Z",
  "url": "https://research.draconitic.com/paper/b1w3cnf2cas6f",
  "venue": "ChemRxiv",
  "versions": []
}