Superior　photocatalytic　activity　and　durability　of　Pt/TiO2　for　decomposing　volatile　organic　pollutants　(typically　aromatic　compounds)　have　been　obtained　by　adding　trace　H2　into　an　O2-rich　photooxidation　system.　The　order　of　photodegradation　efficiencies　for　volatile　organic　compounds　is　cyclohexane　<　acetone　<　benzene　<　toluene　<　ethylbenzene.　Exceptional　stability　of　Pt/TiO2　for　benzene　photodegradation　is　still　maintained　after　22　h　of　testing,　by　the　repeated　use　of　the　catalyst　four　times.　The　promoting　effects　of　H2　in　the　photocatalysis　were　studied　by　infrared　spectroscopy　(IR),　spin-trapping　electron　paramagnetic　resonance　(EPR)　and　surface　photovoltage　spectroscopy　(SPS).　Results　demonstrated　that　the　introduced　H2　has　several　beneficial　effects　on　heterogeneous　photocatalysis,　namely,　a　comparatively　clean　surface　of　Pt/TiO2　with　no　persistent　aromatic　intermediates,　an　increased　number　of　surface　hydroxyl　radicals　in　the　photocatalytic　process,　and　an　enhanced　separation　efficiency　of　photogenerated　electron-hole　pairs.　A　mechanism　is　proposed　to　elucidate　the　promoting　effect　of　H2　on　the　photooxidation　of　volatile　organic　pollutants　over　Pt/TiO2.　©　The　Royal　Society　of　Chemistry　and　the　Centre　National　de　la　Recherche　Scientifique　2005.