Photocatalyst sheet performance under intense UV irradiation and increased temperatures

Abstract

Immobilised nano-particulate photocatalyst sheets offer a simplified approach to scaling water-splitting photocatalytic systems for low-emission hydrogen production. This work investigated the effect of increased UV irradiation and temperature on the water-splitting performance of CoOOH/RhCrO_x/SrTiO₃:Al photocatalyst sheets. UV photon fluxes from 1.75 × 10¹⁹ to over 250 × 10¹⁹ photons per cm² per h were investigated at ambient temperature (23 °C). Although the water-splitting rate increased with increasing intensity, the apparent quantum yield (AQY) was observed to decrease. The effect of temperature on liquid water splitting at 23 °C, 35 °C, 50 °C, 90 °C and 120 °C was further explored upon increasing UV photon flux. It was found that increasing temperatures improve the AQY relative to the photon fluence. The reason for this effect is discussed in terms of bulk and surface effects reducing recombination. A method to equate light sources to solar equivalents was developed and used to relate the UV photon fluxes investigated to concentrated solar equivalents. This work demonstrates the use of heating to improve the efficiency of photocatalytic water splitting, draws attention to the necessity for considering the incident absorbable light intensity in measuring the performance of photocatalysts, and highlights the potential application of photocatalyst sheets under concentrated solar conditions.