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

α, β, γ, and δ polymorphs of 4.6-4.8 eV wide band gap GaO 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-GaO photocatalysts enabled achieving high and stable conversions of toluene with selectivities to CO within the 50-90% range, by contrast to conventional TiO photocatalysts that fully deactivate very rapidly on stream in similar operating conditions with rather no CO production, no matter whether UV-A or UV-C light was used. The highest performances were achieved on the high specific surface area β-GaO photocatalyst synthesized by adding polyethylene glycol (PEG) as porogen before precipitation, with stable toluene conversion and mineralization rate into CO strongly overcoming those obtained on commercial β-GaO. 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 Ga units. In the degradation of hydrogen sulfide, PEG-derived β-GaO 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-GaO photocatalysts. So, we illustrated the interest of using high surface area β-GaO in environmental photocatalysis for gas-phase depollution applications.