Abstracts Book - IMRC 2018

• SC3-O005
EXPERIMENTAL AND THEORETICAL ANALYSIS OF WATER
OXIDATION CATALYSIS ON METAL-OXIDE PHOTOANODES
Camilo A. Mesa Zamora 1 , Laia Francàs 1 , Ke Yang 2 , Pablo Garrido 2,3 , Ernest Pastor 1 , Yimeng Ma 1 ,
Andreas Kafizas 1 , Timothy E. Rosser 4 , Matthew T. Mayer 5 , Erwin Reisner 4 , Michael Grätzel 5 ,
Victor S. Batista 2 , James Durrant 1
1 Imperial College London, Chemistry, United Kingdom, Channel Islands & Isle of Man. 2 Yale
University, Chemistry and Energy Sciences Institute, United States. 3 ICIQ, Institute of Chemical
Research of Catalonia (ICIQ), Spain. 4 University of Cambridge, Chemistry, United Kingdom,
Channel Islands & Isle of Man. 5 EPFL, Institut des Sciences et Ingénierie Chimiques, Swaziland.
Photoelectrochemical water splitting to produce hydrogen, has emerged as a
promising clean and potentially inexpensive renewable solar fuel, when using
semiconductor metal-oxides as both, photoanode and photocathode. Despite
recent advances in more efficient catalysts, water oxidation is still considered
the bottleneck of the overall water splitting process due to its sluggish kinetics,
however the mechanism of reaction and its kinetic consequences remains not
yet well understood. Recently in our group, we have found that 3
photogenerated holes are required to diffuse together at the hematite surface
to overcome the rate determining step of the water oxidation reaction, despite
the 4 oxidative species the overall reaction needs. In this talk, recent advances
on the kinetics of water oxidation taking place on different metal-oxide
photoanodes is presented. Particularly, this talk is focused on a detailed
mechanistic analysis on Si-doped nanocrystalline hematite (α-Fe2O3)
photoanodes at a molecular level, by the study of the water oxidation rate law
under different physicochemical conditions. Here we employed
spectroelectrochemical techniques to study the photogeneration,
recombination and reaction of the photogenerated holes with the electrolyte.
The experimental results combined with DFT calculations enable us to propose
a detailed molecular water oxidation mechanism on hematite, which is found to
have parallels with proposed mechanisms by the enzyme Photosystem II (PSII)
in the natural photosynthesis. These findings suggest that understanding the
natural photosynthesis may lead to further developments in the artificial
photosynthesis field.
Acknowledgment:
J.R.D. acknowledges financial support the European Research Council (project
Intersolar 291482). C.A.M thanks COLCIENCIAS for funding and the Royal Society