Wide band gap Ga2O3 as efficient UV-C photocatalyst for gas-phase degradation applications.

Abstract

α, β, γ, and δ polymorphs of 4.6-4.8eV wide band gap Ga2O3 photocatalysts were prepared via a soft chemistry route. Their photocatalytic activity under 254nm UV-C light in the degradation of gaseous toluene was strongly depending on the polymorph phase. α- and β-Ga2O3 photocatalysts enabled achieving high and stable conversions of toluene with selectivities to CO2 within the 50-90% range, by contrast to conventional TiO2 photocatalysts that fully deactivate very rapidly on stream in similar operating conditions with rather no CO2 production, no matter whether UV-A or UV-C light was used. The highest performances were achieved on the high specific surface area β-Ga2O3 photocatalyst synthesized by adding polyethylene glycol (PEG) as porogen before precipitation, with stable toluene conversion and mineralization rate into CO2 strongly overcoming those obtained on commercial β-Ga2O3. They were attributed to favorable physicochemical properties in terms of high specific surface area, small mean crystallite size, good crystallinity, high pore volume with large size mesopore distribution and appropriate surface acidity, and to the possible existence of a double local internal field within Ga3+ units. In the degradation of hydrogen sulfide, PEG-derived β-Ga2O3 takes advantage from its high specific surface area for storing sulfate, and thus for increasing its resistance to deactivation and the duration at total sulfur removal when compared to other β-Ga2O3 photocatalysts. So, we illustrated the interest of using high surface area β-Ga2O3 in environmental photocatalysis for gas-phase depollution applications.