While nanostructured Fe2O3 (hematite) photoelectrodes are now well established as a means to convert solar energy into fuel via the water splitting reaction, the photocatalytic water oxidation properties of suspended Fe2O3 photocatalysts have not been thoroughly studied. We recently reported that visible irradiation (>400 nm) of suspended Fe2O3 nanocrystals produces oxygen with up to 0.77 mmol h-1 g-1, when silver nitrate is used as a sacrificial electron acceptor. But, reductive deposition of silver deactivates the nanoparticles completely within 18h. Prolonged O2 evolution with only minor catalysts deactivation is possible with NaIO4 as electron acceptor (E0=+1.6 V vs NHE). This allows a systematic investigation of the photocatalytic reaction system. Here we show that the activity increases linearly with illumination intensity, as expected from thermodynamics. It increases asymptotically with sacrificial electron acceptor concentration up to a final threshold that is defined by the water oxidation kinetics.  A similar asymptotic dependence is observed with the Fe2O3 concentration, due to shading. Higher solution pH promotes oxygen evolution, based on thermodynamic reasons.

Optimization of the Fe<sub>2</sub>O<sub>3</sub> (hematite) nanocrystal: NaIO4 photocatalytic water oxidation system

247th National Meeting (2014)

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Optimization of the Fe2O3 (hematite) nanocrystal: NaIO4 photocatalytic water oxidation system

Optimization of the Fe₂O₃ (hematite) nanocrystal: NaIO4 photocatalytic water oxidation system