Research On Modifying The Surface Of Nano-TiO₂ To Load Noble Metal Nanoparticles For Accelerating Hydrogen Evolution And CO₂ Reduction

Photocatalysis is applied to split water and reduce CO₂ for producing hydrogen energy and hydrocarbon fuel,which provides an effective solution for developing clean energy and mitigating greenhouse effect.Nano-TiO₂ has become a hot research object in the field of photocatalysis due to its high catalytic activity,strong photostability,low cost and non-toxicity.However,single TiO₂ as a photocatalyst faces the defect of serious electron-hole recombination,so that noble metals often need to be loaded as co-catalyst to promote the occurrence of surface reduction reaction.Therefore,the intensity of interaction effect between noble metals and nano-TiO₂ surface is crucial to its dispersion and load ratio.In this paper,the surface grafting modification of TiO₂ by inorganic acid and porous polymer,enhance the interaction with noble metal ions and achieve high dispersion and load proportion of noble metals,so as to promote the photocatalytic performance of hydrogen evolution and CO₂ reduction over TiO₂.The main research work is as follows:（1）The spindle-like rutile TiO₂ nanobundles were synthesized by nitrate-group-grafting-induced assembly strategy.The photocatalytic hydrogen production rate of R-TiO₂after loading Pt nanoparticles reached 402.4μmol h^-1,which was 3.1 times higher than that of P25-TiO₂.The grafted nitrate groups on the surface of TiO₂ produced negative field effect,promoting the deposition of Pt co-catalyst,and meanwhile accelerating the capture of positively charged protons during the reaction process,which improved the migration of photogenerated electrons and the reduction of surface protons,thus achieving high efficiency of photocatalytic hydrogen production.（2）The surface of TiO₂ was functionalized with silane coupling agent and grafted by hypercrosslinked N-heterocyclic carbenes polymers（HN）for loading Pd co-catalyst,so as to construct Pd-HN-TiO₂ composite.In the test of photocatalytic CO₂ reduction,Pd-HN-TiO₂ exhibited significantly enhanced CH₄ yield(237.4μmol g^-1 h^-1),which was 38.3 times higher than that of TiO₂,and the selectivity reached 100%.The high specific surface area and the anchorage effect of nitrogen heteroatoms on the surface of TiO₂ by introducing the hypercrosslinked polymer can realize highly dispersion and high loading proportion of Pd nanoparticles（3.84 wt%）,which effectively improves the separation efficiency of photogenerated carriers on the surface of TiO₂,and acts as the hydrogenation center to enhance the activity and selectivity of CO₂ conversion to CH₄.