Wonyong Choi

A systematic study of metal ion doping in quantum (Q)-sized (2-4 nm) TiO_2 colloids is performed by measuring their photoreactivities and the transient charge carrier recombination dynamics. The presence of metal ion dopants in the TiO_2 crystalline matrix significantly influences photoreactivity, charge carrier recombination rates, and interfacial electron-transfer rates. The photoreactivities of 21 metal ion-doped colloids are quantified in terms of both the conduction band electron reduction

High efficiency solar photocatalysis requires an effective separation of photogenerated charge carriers and their rapid transport to the semiconductor interface.

Hydrogen production <italic>via</italic> solar water splitting can be enhanced by combining semiconductors with various 2-dimensional materials.

Polymeric carbon nitride modified with selected heteroatom dopants was prepared and used as a model photocatalyst to identify and understand the key mechanisms required for efficient photoproduction of H₂ O₂ via selective oxygen reduction reaction (ORR). The photochemical production of H₂ O₂ was achieved at a millimolar level per hour under visible-light irradiation along with 100 % apparent quantum yield (in 360-450 nm region) and 96 % selectivity in

Visible light harvesting or utilization through semiconductor photocatalysis is a key technology for solar chemical conversion processes. Although titania nanoparticles are popular as a base material of photocatalysis, the lack of visible light activity needs to be overcome. This mini-review is focused on an uncommon approach to visible light activation of titania: the ligand-to-metal charge transfer (LMCT) that takes place between TiO2 nanoparticles and surface adsorbates under visible light ir

A superior cocatalytic behavior of reduced graphene oxide (rGO) was observed for the photocatalytic production of H2O2 in the TiO2-based system. The adsorption of phosphate on TiO2 enhanced the production of H2O2 up to a millimolar level. The in situ formation of cobalt phosphate on rGO/TiO2 enabled the photocatalytic production of H2O2 even in the absence of organic electron donors.

A variety of combinations of CdS, TiO2, and Pt in preparing the hybrid catalysts were studied for hydrogen production under visible light (λ > 420 nm) irradiation. The preparation method sensitively influenced the activity of the ternary hybrid catalysts. The formation of the potential gradient at the interface between CdS and TiO2 is necessary in achieving the efficient charge separation and transfer and how the platinum as a cocatalyst is loaded onto the CdS/TiO2 hybrid catalysts determines th

Periodate (PI, IO₄^-) can be activated by hydroxylamine (HA), resulting in the rapid removal of organic pollutants within seconds. While the previous studies on PI-based advanced oxidation processes (AOPs) have proposed iodate radical (^•IO₃) as the major reactive species, no evidence of ^•IO₃ production was found in the present PI/HA system. Reactive oxygen species (ROS) including ^•OH, HO₂^•, and <sup

The simultaneous production of hydrogen and degradation of organic pollutants (4-chlorophenol, urea, and urine) was successfully achieved using titania photocatalysts which were modified with both anion adsorbates (fluoride or phosphate) and (noble) metals (Pt, Pd, Au, Ag, Cu, or Ni). The dual-function photocatalysis worked only when both components coexisted on the surface of TiO2, whereas TiO2 modified with a single surface component (F–TiO2, P–TiO2, or Pt/TiO2) was inactive under the same exp