Coupling of light absorbers with catalysts for enhanced photo(electro)catalysis

The development of photochemical systems capable of mimicking the natural photosynthesis by driving useful chemical transformations has attracted significant interest motivated by the need to meet various environmental concerns and to secure the future supply of clean and sustainable energy. The activity, stability, and selectivity of such systems is determined not only by the ability of materials to absorb light and create charges, but also by efficient separation of the charges and their fast and selective reaction with substrates. In this respect, the effective coupling of well-designed co-catalysts with light absorbers plays a crucial role.

The talk will focus on the problem of interfacing different light absorbers with various types of cocatalysts for water remediation^[1] and solar water splitting.^[2,3] One of the most important features of effective cocatalysts in photo(electro)catalytic systems are their optical properties since undesired parasitic absorption of light by the catalysts should be avoided. In this respect, properties of TiO₂ powders modified with single Cu(II) and Fe(III) co-catalytic sites will be discussed. The results demonstrate that the single Cu(II) and Fe(III) ions act as effective cocatalytic sites, enhancing the charge separation, catalyzing “dark” redox reactions at the interface, and improving thus the normally very low quantum yields of UV light-activated TiO₂ photocatalysts.^[1] Similarly, our recent efforts in introducing efficient catalysts into porous photoanodes for light-driven water oxidation will be reviewed. The focus will be on distinct advantages of ultrasmall (1-2 nm) cobalt oxyhydroxide nanoclusters as compared to more conventional (larger) cocatalyst particles.^[3] Finally, strong electrolytes effects on the photoanode performance will be discussed based on photoelectrochemical and spectroscopic investigations, combined by theoretical calculations.