Charge Concentration Limits the Hydrogen Evolution Rate in Organic Nanoparticle Photocatalysts: Article No. 2210481

Max O'Connor, Taylor Aubry, Obadiah Reid, Garry Rumbles

Research output: Contribution to journalArticlepeer-review

2 Scopus Citations

Abstract

Colloidal organic nanoparticles have proven to be a promising class of photocatalyst for performing the Hydrogen Evolution Reaction (HER) due to their dispersibility in aqueous environments, their strong absorption within the visible region, and the tunabilty of their component materials' redox potentials. Currently, there is little understanding of how charge generation and accumulation in organic semiconductors change when these materials are formed into nanoparticles that share a high interfacial area with water, nor is it known what mechanism limits the hydrogen evolution efficiency in recent reports on organic nanoparticle photocatalysts. Herein, we use Time-Resolved Microwave Conductivity to study aqueous-soluble organic nanoparticles and bulk thin films composed of various blend ratios of the non-fullerene acceptor EH-IDTBR and conjugated polymer PTB7-Th and examine the relationship between composition, interfacial surface area, charge carrier dynamics, and photocatalytic activity. We quantitatively measure the rate of Hydrogen Evolution Reaction by nanoparticles composed of various donor:acceptor blend ratio compositions and find that the most active blend ratio displays a Hydrogen Quantum Yield of 0.83% per photon. Moreover, we find that nanoparticle photocatalytic activity corresponds directly to charge generation, and that nanoparticles have 3x more long-lived accumulated charges relative to bulk samples of the same material composition. These results suggest that, under our current reaction conditions, with approximately 3x solar flux, catalytic activity by these nanoparticles is limited by the concentration of electrons and holes in operando and not a finite number of active surface cites or the catalytic rate at the interface. This provides a clear design goal for the next generation of efficient photocatalytic nanoparticles.
Original languageAmerican English
Number of pages7
JournalAdvanced Materials
Volume36
Issue number20
DOIs
StatePublished - 2024

Bibliographical note

See NREL/JA-5900-82767 for ChemRxiv preprint

NREL Publication Number

  • NREL/JA-5900-84559

Keywords

  • EH-IDTBR
  • exciton-charge annihilation
  • hydrogen evolution
  • microwave conductivity
  • organic nanoparticle
  • PTB7-Th
  • solar-photochemistry
  • TRMC

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