Solvent-controlled O2diffusion enables air-tolerant solar hydrogen generation

Michael G. Allan; Morgan J. McKee; Frank Marken; Moritz F. Kuehnel

doi:10.1039/d1ee01822a

Solvent-controlled O₂diffusion enables air-tolerant solar hydrogen generation

Michael G. Allan, Morgan J. McKee, Frank Marken, Moritz F. Kuehnel

Research output: Contribution to journal › Article › peer-review

8 Citations (SciVal)

Abstract

Solar water splitting into H2 and O2 is a promising approach to provide renewable fuels. However, the presence of O2 hampers H2 generation and most photocatalysts show a major drop in activity in air without synthetic modification. Here, we demonstrate efficient H2 evolution in air, simply enabled by controlling O2 diffusion in the solvent. We show that in deep eutectic solvents (DESs), photocatalysts retain up to 97% of their H2 evolution activity and quantum efficiency under aerobic conditions whereas in water, the same catalysts are almost entirely quenched. Solvent-induced O2 tolerance is achieved by H2 generation outcompeting O2-induced quenching due to low O2 diffusivities in DESs combined with low O2 solubilities. Using this mechanism, we derive design rules and demonstrate that applying these rules to H2 generation in water can enhance O2 tolerance to >34%. The simplicity and generality of this approach paves the way for enhancing water splitting without adding complexity.

Original language	English
Pages (from-to)	5523-5529
Number of pages	7
Journal	Energy and Environmental Science
Volume	14
Issue number	10
Early online date	31 Aug 2021
DOIs	https://doi.org/10.1039/d1ee01822a
Publication status	Published - 1 Oct 2021

Bibliographical note

Funding Information:
This work was supported by EPSRC through a DTA studentship to MGA (EP/R51312X/1), and a capital investment grant to MFK (EP/S017925/1). We thank Swansea University for providing start-up funds to MFK. We thank Prof. Alex Cowan and Dr Gaia Neri (University of Liverpool) for recording DR-UV spectra. We wish to thank Julian Kivell and Phil Hopkins in the Swansea University mechanical workshop for their assistance with the experimental setup. MFK is grateful to the Ernst Schering Foundation for support.

Data availability
Raw experimental data is openly available via dx.doi.org/10.5281/zenodo.5236823.

Funding

This work was supported by EPSRC through a DTA studentship to MGA (EP/R51312X/1), and a capital investment grant to MFK (EP/S017925/1). We thank Swansea University for providing start-up funds to MFK. We thank Prof. Alex Cowan and Dr Gaia Neri (University of Liverpool) for recording DR-UV spectra. We wish to thank Julian Kivell and Phil Hopkins in the Swansea University mechanical workshop for their assistance with the experimental setup. MFK is grateful to the Ernst Schering Foundation for support.

ASJC Scopus subject areas

Environmental Chemistry
Renewable Energy, Sustainability and the Environment
Nuclear Energy and Engineering
Pollution

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1039/d1ee01822aLicence: CC BY

Cite this

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title = "Solvent-controlled O2diffusion enables air-tolerant solar hydrogen generation",

abstract = "Solar water splitting into H2 and O2 is a promising approach to provide renewable fuels. However, the presence of O2 hampers H2 generation and most photocatalysts show a major drop in activity in air without synthetic modification. Here, we demonstrate efficient H2 evolution in air, simply enabled by controlling O2 diffusion in the solvent. We show that in deep eutectic solvents (DESs), photocatalysts retain up to 97% of their H2 evolution activity and quantum efficiency under aerobic conditions whereas in water, the same catalysts are almost entirely quenched. Solvent-induced O2 tolerance is achieved by H2 generation outcompeting O2-induced quenching due to low O2 diffusivities in DESs combined with low O2 solubilities. Using this mechanism, we derive design rules and demonstrate that applying these rules to H2 generation in water can enhance O2 tolerance to >34%. The simplicity and generality of this approach paves the way for enhancing water splitting without adding complexity. ",

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