Study On The Modification Of Titania-based Photocatalysts

Hydrogen is a renewable and environmental-friendly energy resource andbelieved to be one of the best choices to replace fossil fuel to mitigate CO2emissions.Photocatalytic hydrogen production from water decomposition under sunlightirradiation also becomes one of the best sources of hydrogen. TiO2has beenconsidered one of the most promising photocatalysts for photocatalytic hydrogengeneration due to its unique photoelectric properties, long-term thermal and chemicalstability, non-toxicity and low cost. However, the limited optical response only to UVlight and the fast recombination of photogenerated electron-hole pairs on TiO2lead toa low quantum efficiency of photocatalytic hydrogen evolution. And modifying TiO2,to improve the photocatalytic activity of TiO2, becomes the focus of our topic. In thispaper, our attention is focused on doping TiO2with CuO, GR and N to investigate thephotocatalytic activity of P25. Through analyzing the structure of the composite, thefunction of the doping components on TiO2can be analyzed in theory.Firstly, the photocatalytic activity of CuO/TiO2was systematically investigatedunder various conditions. The results suggested that there was an optimum operatingcondition:2~7.5wt%of Cu content,350℃of calcination temperature and0.6~1.0g/L of scattered catalyst amount. Hydrogen production rate of2wt%CuO/TiO2couldreach to1022μmol/(h·g) under the condition of10vol%methanol concentration,350℃calcination temperature and1.0g/L scattered catalyst amount. At the sametime,2wt%CuO/TiO2photocatalyst had a stable photocatalytic activity for H2evolution.Combine the novel carbon material graphene with TiO2under hydrothermaltreatment to prepare graphene doped TiO2or CuO/TiO2photocatalysts. Theninvestigate the effect of the addition of graphene on TiO2and CuO/TiO2. The resultssuggested that the hydrogen evolution rate of TiO2-GR and CuO/TiO2-GR is1.9and2.1times larger than P25and CuO/TiO2. The hydrogen evolution rate ofCuO/TiO2-GR-0.5reached to2905μmol/(h·g). It is also demonstrated that a chemicalbond formed between GR and TiO2in CuO/TiO2-GR composites, which is benefit forthe transmission and transfer of electrons. CuO/TiO2-GR composites had a higherphotocatalytic activity for hydrogen production due to a synergistic effect betweenCuO and GR. The synergistic effect could efficiently suppress charge recombination, improve interfacial charge transfer, enhance visible-light adsorption and provideplentiful phtotocatalytic reaction active sites.Finally, we investigated the effect of N doped titania-based photocatalysts. TheN-TiO2photocatalysts were prepared by high-temperature roasting, plasma processing,impregnation method, mechanical trituration and hydrothermal processing. It wasfound that the catalyst prepared by impregnation method showed the bestphotocatalytic activity in all kinds of N doped TiO2photocatalsts. Meanwhile, N, GR,CuO co-doped P25photacatalysts also showed much higher photocatalytic activitythan TiO2-GR and CuO/TiO2-GR, as the doption of N can further enhance the abilityof graphene for transmitting and transferring electrons.