Photocatalytic and electrocatalytic pathways to sustainable fuels and chemicals: insights into reaction kinetics from optical spectroscopy

James Durrant

Professor of Photochemistry, Imperial College

Abstract

Durrant will begin the discussion by introducing the challenge of sustainably synthesizing fuels and chemicals as part of the transition to a more sustainable energy system. He will introduce photocatalytic, photoelectrode, and electrocatalytic pathways to sustainable fuels and chemicals. The use of transient optical spectroscopies to provide insight into both photocatalytic and electrocatalytic functions will be discussed, focusing in particular on the challenge of splitting water to synthesize green hydrogen and the organic oxidations (e.g. photoreforming). 

Durrant will highlight the particular kinetic challenge for photocatalysis resulting from the timescale mismatch between the picosecond to nanosecond lifetimes of photoexcitations in most light-absorbing materials versus the microsecond to second timescales of chemical fuel synthesis, and contrast this with kinetic challenges in photovoltaic solar cells. He will give examples of photocatalytic approaches employing organic and inorganic materials, including metal oxides and conjugated polymers, and how transient optical spectroscopies can give insight into their function. 

Durrant will move on to the challenge of water oxidation catalysis, the key kinetic and thermodynamic bottleneck for both photocatalytic and electrocatalytic water splitting. He’ll again illustrate how transient optical spectroscopies to used to provide insight into catalyst function. In particular, he will show how operando optical spectroelectrochemistry can be used to determine redox state population densities and catalysis kinetics in metal oxides electrocatalysts and photocatalysts during water oxidation. This spectroelectrochemical approach is based on the idea that the redox states of most transition metal oxides are colored, allowing the specific concentrations of each state to be tracked by their optical absorption/reflection as a function of material, applied bias, time, electrolyte, etc. 

Durrant will demonstrate how such optical analyses can yield insights difficult to achieve from more widely employed electrochemical analyses. He’ll discuss examples of the insights gained from such operando spectroelectrochemistry into materials design and function, for example comparing water oxidation kinetics on heterogeneous and molecular iridium electrocatalysts, as well as on hematite photoelectrodes.

Bio

James Durrant is a British photochemist and professor of photochemistry at Imperial College London and Sêr Cymru Solar Professor at Swansea University. He serves as director of the center for plastic electronics. Durrant was educated at Gresham’s School in Norfolk, the University of Cambridge and Imperial College London, where he was awarded a Ph.D. in 1991 for research on photosystem II using spectroscopy. Durrant’s research focuses on a range of photochemical applications including solar cells, solar fuel production and photocatalysis, nanomaterials and plastic electronics.