Study On CO₂ Photodissociation Over Hydroxyl Modification SrTiO_3-x

Strontium titanate（SrTiO₃）is a kind of wide-bandgap n-type semiconductor that is non-toxic and stable.Due to its suitable potentials of conduction band and valence band,SrTiO₃ can satisfy the thermodynamic conditions for all kinds of photocatalytic applications,such as photocatalytic water splitting,photodegradation of organic pollutants and CO₂ photoreduction.However,the bandgap of SrTiO₃ is3.4 eV,thus it can only absorb ultraviolet light that accounts for a tiny fraction of the solar spectrum,which seriously restricts its photocatalytic efficiency.Surface/interface modulation can extend the spectral response of semiconductor and promote the utilization of photocarriers;however,the present studies are confined to simplex modulation method.In this thesis,introduction of surface oxygen defect and grafting of hydroxyl group as a complex surface/interface modulation was applied over SrTiO₃,which helps to enhance its performance of CO₂ photodissociation.The main results and conclusions are as below.The mixture of commercially-available SrTiO₃ and sodium borohydride（NaBH₄）was sintered in argon atmosphere to produce oxygen-vacancy contained SrTiO₃ sample(SrTiO_3-x),which the concentration of oxygen defect could be controlled by the calcination temperature;further,the alkalization treatment made SrTiO_3-x-x graft with hydroxyl groups to generate the final product of hydroxyl modified SrTiO_3-x.In the test of CO₂ photodissociation under visible-light irradiation,the sample under optimal synthesis could achieve 11.7 and 1.6-fold enhancements compared with the pristine SrTiO₃ and SrTiO_3-x samples,respectively.Especially,the hydroxyl modified SrTiO_3-x can dissociate CO₂ to CO under near-infrared-light irradiation,which makes significance advance in the utilization of whole solar spectrum.The enhanced performance for CO₂ dissociation can be attributed to two aspects:on the one hand,the surface oxygen defect and hydroxyl group of SrTiO₃ is beneficial for the adsorption and activation of CO₂;on the other hand,the oxygen vacancy-coexisted Ti³⁺and hydroxyl group can serve as sacrificial reagent to efficiently capture photoholes,which retains the stability of the whole reaction.The study achieves direct dissociation of CO₂ to CO with full-spectral response for the first time and proposes new opinion to the reaction pathway of CO₂photoreduction.The complex surface/interface modulation method provides a new and effective route to develop high-efficient photocatalytic materials.