Synthesis Of TiO₂-based Nanomaterials And Properties Of Photocatalytic CO₂ Reduction

CO₂photocatalytic technology utilizes rich solar energy to convert CO₂into CO or CH₄,etc.,which can simultaneously solve global climate warming and energy supply crisis issues.Developing highly active and stable photocatalysts is the focus of this technology.Ti O₂has a wide focus on low cost,good long-term stability,environmentally friendly,non-toxic and other benefits.However,there is a shortcoming of the visible light response range narrow range,low photocatalytic efficiency and poor product selection.This paper is modified for Ti O₂through different strategies.The selectivity and activity of the reduction product is improved by enhance the separation efficiency of the photocarriers and visible light response capability.And study the characteristics and reaction mechanism of catalyst photocatalytic reduction CO₂.The main research contents and results of this paper are as follows:(1)Ti O₂was modified by non-metal doping strategies.With a simple and adjustable co-precipitation method,NH₃·H₂O is nitrogen source,and a series of in situ N-doped Ti O₂(x N-Ti O₂)having different N content is prepared by controlling NH₃·H₂O content,thereby performing photocatalytic reduction CO₂reaction.The morphology,structure,photoelectrochemical properties,and surface adsorption CO₂capability of x N-Ti O₂photocatalyst were analyzed by XRD,SEM,TEM,XPS,and UV-vis.The possible mechanism of photocatalytic reduction CO₂is further predicted by the in situ FTIR.The results show that the photocatalytic performance of 10N-Ti O₂is preferably 97.8?mol g^-1h^-1,of 2.3 and 3 times of P25 and A-Ti O₂,respectively.The photocatalytic reduction performance of CO₂mainly depends on the following three points:First,N doping improves the visible light response ability,optimizing the band structure,reducing the photon energy required for electron excitation.Second,a large number of OVs presence provides the adsorption site to the CO₂,thereby increasing the reactive site.Finally,the presence of N 2p energy level and OVs accelerates the separation of carriers and improves the reduction ability of optical electronics.Therefore,N-doping and doping caused OVs facilitates the promotion of photocatalytic properties.(2)The N-Ti O₂is further modified by the precious metal modification and semiconductor composite strategies.The photocatalytic reduction CO₂reaction was prepared by simple hydrothermal method.Ternary Z-scheme Au/N-Ti O₂/g-C₃N₄(Au/N-Ti O₂/CN)photocatalyst was prepared by simple hydrothermal method for the photocatalytic reduction of CO₂.XRD,TEM and XPS were used to characterize the crystal structure,microstructure,surface elemental composition and elemental state.The photocatalytic properties of the catalysts were analyzed by UV-vis and impedance spectroscopy,and the influence mechanism of noble metal loading and heterostructure on the activity of photocatalytic reduction of CO₂was further discussed.The results show that Z-scheme photocatalyst Au/N-Ti O₂/CN not only improves the yield of CO,but also improves the yield and selectivity of CH₄,and the selectivity of CH₄increases from 0 to 26%.Among them,the SPR effect of precious metal Au not only improves the absorption performance of visible light,but also acts as a bridge for electron transfer.The photogenerated electrons at a relatively lower position in the N-Ti O₂conduction band are preferentially transferred to Au nanoparticles,and then to the valence band of the adjacent CN nanosheet,and then recombine with its holes.The Z-scheme heterojunction improves the separation efficiency of carriers,and the photogenerated electrons are retained and enriched in the conduction band of CN with higher reduction potential,thus improving the reduction ability of photogenerated electrons.Therefore,the synergistic effect between noble metal loading and heterostructure construction can improve the performance of photocatalytic reduction of CO₂.