Assessing the photocatalytic oxygen evolution reaction of BiFeO3 loaded with IrO2 nanoparticles as cocatalyst

Abstract

Oxygen evolution is kinetically the key step in the photocatalytic water splitting, but it is negatively affected by the poor charge transport properties. However, this can be modified by the loading of cocatalysts on the surface of a semiconductor which could form heterojunctions to boost the charge separation and lower the activation potential for O 2 evolution. In this paper we demonstrate that the poor O 2 evolution activity of photocatalytic water splitting of the multiferroics BiFeO 3 can be enhanced when a proper cocatalyst like IrO 2 nanoparticles are deposited on the surface and proper electron scavenger is used. The choice of the persulfate, S 2 O 8 as electron scavenger is influenced by its high redox potential and its close position to the valence band of BiFeO 3 compared to other commonly used scavengers. Another interesting information was revealed by using transient absorption spectroscopy under different environment namely, inert, oxidizing and reducing. The absorption peak of holes was identified and correlated to the strong absorption around 560 nm The hole absorption peak showed a 50% decrease in the absorption intensity after 2.5 μsec indicating that holes are captured by IrO 2 nanoparticles on the surface. O 2 evolution of multiferroics, especially BiFeO 3 has been less investigated. Therefore, the development of efficient photocatalytic materials has relied on both photocatalysts and cocatalysts. Identification of the photogenerated charge absorption peak from transient absorption spectra facilitate the evaluation of the IrO 2 loading effect on the charge separation and the overall O 2 evolution process. • Visible light photocatalytic OER of BiFeO 3 nanoparticles. • Enhancement of OER by loading IrO 2 nanoparticles as cocatalyst on the surface of BiFeO 3 . • Volcanic type dependance of oxygen evolution and IrO2 loading content. • Identification of the absorption signal of the photogenerated charges by TAS, measured in N 2 , MeOH and O 2 atmosphere. • A signal at 560 nm was assigned to holes as indicated from TAS measurements.