Preparation Of M/TiO₂（M＝Pt、Ru、Pd） Nanotube Arrays And Research On Photoelectric Catalysis Performance

Environmental pollution and energy shortage are the two major challenges humanity faced.Semiconductor materials and nano technology provide a new thinking to solve these two problems.TiO2 was applied widely in the field of photoelectric conversion and catalytic because of their excellent physical and chemical stability, and a rich source.TiO2 nanotubes（NTs） as one of the most common form of TiO2, have been widely used in the fuel cell field and CO₂ reduction as catalytic electrode because of its large specific surface area, high catalytic efficiency, nontoxic,good chemical stability and other advantages. However, the wide band gap of TiO2 limits their utilization rate. Moreover, their poor electrical conductivity, high recombination rate of photo-electron and hole limits its photoelectrochemical catalytic application. So, how to modify TiO2 to improve its quantum efficiency and photocatalytic properties is one of the most important works in the photocatalytic fields. The paper focuses on the research of TiO2 modification and the investigation on the catalytic efficiency. Graphene and noble metals were electrodeposited on the resulting TiO2 NTs. Methanol oxidation and photocatalytic reduction of CO₂ were performed on the as-prepared TiO2 composites.The main research results are listed as follows:（1） TiO2 NTs with uniform aperture and highly ordered structure were growen on Ti wire by anodization. A highly electric conductivity carbon-modified TiO2 nanotube（RGO-TiO2 NTs） array is fabricated by depositing ruduced graphene oxide（RGO） onto TiO2 NTs. Using the RGO-TNTs as working electrode, the well dispersed Pt-Ru nanoparticles（NPs） are electrochemically deposited in sequence on the RGO-TiO2 NTs from the H2PtCl6 and RuCl3 under the room tempreture with diameters of 4-5 nm. PtRu precipitation amoun was regulated by controlling the sedimentary cycles. Influence of variable Pt/Ru ration of 1:0,1:1; 1.25:1,1.5:1, 1.75:1 and 2:1 was detected on the methanol oxidation. The optimum Pt/Ru mole ratio was selected through comparative analysis.（2） PtRu-alloy-RGO-TNTs were fabricated by electrochemical deposition with H2PtCl6 and RuCl3 mixed solution as electrolyte. The PtRu alloy particles with diameter of ca. 50 nm are made up of small crystal nucleuses（2 nm）. In this structure, the TNTs serve as nano supporter and the RGO layers act as electron transportor. A much better electrocatalysis performance was obtained by the synergism of the PtRu alloy nanoparticles during the methanol oxidation reaction than the PtRu-RGO-TiO2 NTs which is deposited in sequence. Depositing partly RGO on the surface of TiO2 NTs can significantly enhance the electric conductivity, which can improve the well dispersion of PtRu NPs, and facilitate charge transfer during the methanol electrocatalysis oxidation reaction, and remove the harmful byproduct CO-like species. A superior stability was investigated from 30°C to 70°C.（3） Pd-RGO-TNTs composite have been fabricated via an electrochemical deposition method in a three-electrode system using PdCl2 solution as the electrolyte and the RGO-TiO2 NTs as working electrode.To explore the photoelectric properties of the catalysts, DRS spectra, Fluorescence emission spectra, Photocurrent responses EIS spectra were analyzed.The experimental results showed that the Pd-RGO-TNTs composite exhibited excellent photoelectric properties. The Pd-RGO-TNTs composite successfully turn CO₂ into CH3 OH and C2H5 OH under photoelectric condition. The evolution of CH3 OH and C2H5 OH were 1624 nmol/cm2?hr and 536 nmol/cm2?hr.