Wide band gap Ga 2 O 3 as efficient UV-C photocatalyst for gas-phase degradation applications

Abstract

α, β, γ, and δ polymorphs of 4.6–4.8 eV wide band gap Ga₂O₃ photocatalysts were prepared via a soft chemistry route. Their photocatalytic activity under 254 nm 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.