Role of Water Oxidation Catalyst IrO₂ in Shuttling Photogenerated Holes Across TiO₂ Interface

Abstract

Iridium oxide, a water oxidation cocatalyst, plays an important role in mediating the hole transfer process of a UV-irradiated TiO2 system. Spectroscopic identification of trapped holes has enabled their characterization in colloidal TiO2 suspension and monitoring of the transfer of trapped holes to IrO2. Titration of trapped holes with potassium iodide yields an estimate of three holes per particle during 7 min of UV irradiation of TiO2 suspension in ethanol containing 5% acetic acid. The hole transfer to IrO2 occurs with a rate constant of 6 × 105 s–1. Interestingly, IrO2 also catalyzes the recombination of trapped holes with reduced oxygen species. The results discussed here provide a mechanistic and kinetic insight into the catalytic role of IrO2 in the photogenerated hole transfer process.

In situ self-transformation synthesis of g-C3N4-modified CdS heterostructure with enhanced photocatalytic activity

“…However, further loading of g-C 3 N 4 amount into the g-C 3 N 4 /CdS composites will slightly decrease the rate of hydrogen production because high g-C 3 N 4 loading amount could result in covering active sites on the surface of CdS and hindering its contact with sacrificial reagents. The present mechanism of g-C 3 N 4 cocatalyst-modified CdS is similar to the well-known hole-cocatalyst modified photocatalysts such as IrO 2 -TiO 2 , MnO x -TiO 2 , and CoO x -TiO 2 [47][48][49]. Apparently, the strongly coupling interface of g-C 3 N 4 /CdS heterostructure is a crucial factor for the enhanced hydrogen production, which is very beneficial to the rapid transfer of photogenerated holes from CdS to g-C 3 N 4 cocatalyst.…”

Morphology-sensitive trapping states of photogenerated charge carriers on SrTiO3 particles studied by time-resolved visible to Mid-IR absorption spectroscopy: The effects of molten salt flux treatments

“…Trapped electrons and holes in mid-gap states also give transient absorption peaks in the visible or near-IR (NIR) regions [21][22][23][24][25][26][27]; therefore, the energy states of photogenerated charge carriers as well as the decay processes can be examined. We have demonstrated the effectiveness of this method in elucidating the behavior of photogenerated charge carriers in CoO x -loaded LaTiO 2 N [10], which is the most efficient photocatalyst for oxidizing water under visible light.…”

Evolution of electronic correlations across the rutile, perovskite, and Ruddelsden-Popper iridates with octahedral connectivity

“…These include novel magnetotransport, with a large spin Hall angle which clearly highlights the importance of spin-orbit coupling 19 , as well as a Hall effect whose carrier sign can be switched by changing the orientation of the external magnetic field 20 . In addition, IrO 2 is a very promising catalyst for the oxygen evolution reaction 21,22 . Given its similar local structure, one might expect IrO 2 to share many of the same properties as the other iridates.…”