Study Of TiO₂-based Composite Photocatalysts For Hydrogen Evolution From Formic Acid

Hydrogen has attracted wide attention as a clean energy source for sustainable development.The use of heterogeneous photocatalysts for decomposing hydrogen from formic acid to obtain clean fuels has important practical significance.In this dissertation,the photocatalytic,composition of formic acid to titania-based composite photocatalyst was studied.X-Ray Photoelectron Spectroscopy(XRD),Scanning Electron Microscopy(SEM),High Resolution Transmission Electron Microscopy(HRTEM),and other characterization methods were used to explore the relationship between photocatalytic structure and catalytic reaction performance.The main findings are as follows:A simple sol-gel method by calcinating titanium dioxide precursor with gold and lanthanum in heat treatment under H2/CO2 atmosphere has been proposed to prepare highly photocatalytic Au-La2O3/TiO2(ALT)hybrid.Characterization results show that gold nanoparticles with small particle size are embedded in a nearly homogeneous component,which may induce a strong interaction between the components.La and Au co-doping can obtain an appropriately modified bandgap structure and extend the absorption edge to visible light region.The formation of La2O2CO3 on the surface could facilitate to the basicity optimization of the photocatalyst and contribute to the C-H bond cleavage in HCOO-to release H2 and CO2 from formic acid(FA).The large surface area and mesopores structure could provide more active sites for the adsorption of reactant molecules and improve the photocatalytic activity.Benefiting from these positive effects,the ALT photocatalyst calcinating in H2/CO2 demonstrated great photocatalytic property and produced an optimal H2 generation rate of 178.4?mol·gcat-1·h-1 under simulated sunlight irradiation,which was approximately 1.3,1.9 and 2.6 times higher than the same photocatalysts calcinating in H2,CO2,and N2,respectively.Sandwich-like multi-layer structured composite photocatalyst was prepared by doping reduced graphene with good charge transport properties and lanthanum into titanium dioxide.La2O3/TiO2-rGO broadens the visible light absorption capacity,and has better electron-hole separation ability than TiO2,La2O3/TiO2 and TiO2-rGO.The hydrogen production rate from formic acid under visible light is obviously improved.After continuous reaction for 90 h,the rate of hydrogen production from the decomposition of formic acid remains at approximate 1150 ?mol·gcat-1·h-1.The characterization results show that the strong interaction between graphene and titanium dioxide and lanthanum oxide in the sandwich structure promotes the transfer of photoelectrons and inhibits the recombination of carriers.