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INTERSOLAR Report Summary

Project ID: 291482
Funded under: FP7-IDEAS-ERC
Country: United Kingdom

Final Report Summary - INTERSOLAR (Rectifying interfaces for solar driven fuel synthesis)

Solar Energy is the largest renewable energy resource available to mankind, where the solar irradiation on the planet in just one hour exceeds our current annual global energy demand. There is rapidly growing interest in the science of converting solar energy into molecular fuels. This has been motivated by the need to develop renewable transportation fuels as well as the intermittency of solar electrical power.
The natural phenomenon of plant photosynthesis demonstrates the viability to convert sunlight into chemical fuels, thus storing the incident solar irradiation in the form of chemical bonds. This phenomenon can be mimicked in certain inorganic semiconductor materials, where such materials have been aptly named “artificial leaves”. Current approaches to solar driven fuel synthesis can broadly be divided into three different semiconductor materials approaches: inorganic photoelectrodes, nanoparticle suspensions and sensitised molecular catalysts. We have investigated the flow of charges in all three approaches, leading to a greater understanding of current limitations in each case.
This proposal has addressed the need to develop efficient photoelectrodes for solar driven fuel synthesis, where we have focussed on the generation of hydrogen fuel from the photolysis of water (H2O -> H2 + O2). We have previously demonstrated how transient absorption spectroscopy is the choice method in characterising electron transfer dynamics and bulk electron-hole recombination dynamics in such photoelectrodes. In the photoelectrodes we have examined, our studies showed how the kinetics of water oxidation remarkably slow (100’s of milliseconds – seconds), emphasising the need for catalysts that can accelerate these kinetics, and thereby reduce efficiency losses. A key focus of this proposal was to attach catalysts onto the surface of our photoelectrodes to enhance the efficiency of fuel synthesis, thus exploiting recent advances in the syntheses of such catalysts. We have investigated many catalyst layers, and can broadly distinguish catalyst systems that improve performance solely through charge separation (e.g. CoOx, CoPi) and those that are actively involved in the water oxidation (e.g. Ni(Fe)OOH). Moreover, this project has applied the use of high sensitivity transient laser spectroscopies to determine the relationship between materials structure and device function. Our contributions in this matter have been of particular importance since there were very few publications on the transient kinetics of fuel synthesis from photoelectrodes as the onset of this project.
We have also developed a new method of determining the kinetics of water photolysis at light levels similar to operating conditions using simple LED irradiation. This technique fulfils a long-standing need to understanding the kinetics of water photolysis at operating conditions and should be of true and lasting benefit to the scientific community. We have applied this new method to the world’s leading photoelectrode materials, including hematite (a-Fe2O3), bismuth vanadate (BiVO4), and cuprous oxide (Cu2O). We have gained valuable information on charge accumulation and novel insights regarding the mechanism of water and methanol oxidation by metal oxides. By coming to an in depth understanding of the best photoelectrode materials we have available, we should be able to guide future design of next generation materials. We have explored the photophysics of low cost carbon-based photocatalyst, and have been at the forefront in rationalising their unexpected potential for solar fuel production. In addition, our research molecular catalysts is providing greater insight into the requirements for efficient catalytic function and is paving the way for effective catalyst design and attachment strategies.

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United Kingdom
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