Tailoring morphology and co-catalyst loading of LaTiO2N particles for solar water splitting

Oral, Simone Pokrant, presentation 015
Publication date: 16th April 2014

The development of a sustainable energy economy, based not on limited fossil fuels, but on renewable, carbon-neutral energy is a necessary and urgent task. Hydrogen is a leading candidate for the storage and transportation of energy provided it can be efficiently produced from renewable energy sources. Solar energy, the largest renewable source, has the potential to provide sufficient power for carbon neutral H₂ production via water hydrolysis on the scale required. Photocatalytic and photoelectrochemical water splitting are two promising possibilities how to store solar energy in chemical bonds [1].
One highly relevant question is which material can be used best as a photocatalyst. The list of the necessary material properties for photocatalysts optimized for O₂ and/or H₂ production is long: It should be cheap, easy to produce, non-toxic and contain only earth-abundant elements [2]. To harvest sun light efficiently, the material should absorb in the wavelength range of the visible light. Moreover, the quantum efficiency needs to be high, as well as the catalytic activity either for O₂ and/or H₂ production, often achieved by using co-catalysts. Large surface area and good charge-transport properties are key features to an enhanced device performance [2]. This is why mesoporosity in single crystals has lately received highest attention. Their improved electron conductivity compared to nanocrystalline materials has been demonstrated as well as their large surface area [3].
In this context oxynitrides are a highly interesting material class [4]. They are synthesized via solid state reactions which allow tuning the morphology. The morphology range stretches from small dense particles to large mesoporous single crystals [5]. Hence oxynitrides represent perfect model systems to study the effect of morphology changes on the photocatalytic properties.  
In this contribution we will compare the photocatalytical and the photoelectrochemical performance of four different morphologies obtained for the oxynitride LaTiO₂N. Their microstructure will be analyzed focusing on mesoporosity by transmission electron microscopy. We will also show how changes in the LaTiO₂N morphology affect the CoO_x co-catalyst formation and performance.
[1]    B.A. Pinaud, et al., Energy Environ. Sci.,  6 (2013) 1983.
[2]    T. Hisatomi, et al., Chem Soc Rev, (2014).
[3]    E.J.W. Crossland, et al., Nature,  495 (2013) 215.
[4]    K. Maeda, Phys. Chem. Chem. Phys.,  15 (2013) 10537.
[5]    A.E. Maegli, et al. , J. Phys. Chem. C, (2013).

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