Preparation Of Polypyrrole/TiO₂Nanotube Arrays Nanocomposite And Its Photoelectrochemical Properties

Organic-inorganic heterojunction materials formed by conducting polymerpolypyrrole and TiO₂nanotuber arrays are a kind of novel electrode material. It haspotential application in the field of solar cell and photocatalytic degradation of organicpollutants.In this paper, we prepared the polypyrrole modified TiO₂nanotube arrayscomposite material electrodes by two steps. Firstly, highly ordered TiO₂nanotube arrayswere anodized Ti foil in aqueous solution containing fluoride at a low voltage. Secondly,polypyrrole were electropolymerized on TiO₂nanotube arrays by potentiostaticmethod.The amount of polypyrrole modified TiO₂nanotuber arrays can be strictlycontrolled by potentiostatic experimental conditions.①The appearance of the polypyrrole is affected by polymerization time,polymerization temperature, polymerization potential and electrolyte concentration. Aseries of PPy/TiO₂nanocomposites were prepared unde the different experimentalconditions. The characterization of nanocomposites was performed by SEM. Theexperimental results demonstrated that The PPy/TiO₂nanocomposite were prepared at20℃, in0.10mol/L pyrrole monomer and0.10mol/L sodiumdodecylbenzenesulfonate（SDBS） solution, under the constant potential of1.0Vpolymerization30s, has the best morphology. The composites were characterized byFTIR and UV-Vis. The results showed that, compared with bare TiO₂NTs, there was astrong interaction between polypyrrole and TiO₂,which caused increased the lightabsorption in visible light region.②PPy/TiO₂NTs composites were prepared in different polymerization time, andstudied modified effect by incident photo conversion efficiency and EIS.The resultshows that the visible light as the light source, PPy/TiO₂nanocomposites have thelargest photocurrent when the polymerization time is30s, and the incident photoconversion efficiency is up to1.81%in the550nm wavelength. And from the propertiesof conductivity perspective, electrochemical impedance spectroscopy was confirmed thepolymerization time was30s,the conductivity of composites was the highest.This is dueto thin polypyrrole did not achieve the effect of modified, and instead, thick PPy filmabsorb photon and decrease the intensity of light, affect the electron transfer and reduceconductivity of composites. The result was ascribed to the presence of narrow band gapp-type conducting polymer semiconductor PPy enhancing visible-light absorption and decreasing the recombination of photo electron-hole result in enhanced photocurrent.③The presence of dopant will affect the conductivity of polypyrrole.In this paper,methyl orange （MO） and sodium dodecylbenzenesulfonate （SDBS）, with the samesulfonic acid group, as dopants to preparation of PPy/TiO₂nanocomposites anddiscussed impact of dopant on photoelectrochemical properties.It was found thatinstantaneous photocurrent of SDBS/PPy/TiO₂was significantly larger thenMO/PPy/TiO₂.On the one hand, it can be explained from the perspective of molecularstructure. Due to the molecular structure of MO was significantly greater than SDBS,and MO will be attached to the skeleton of PPy, disturbed the arrangement of the PPymain chain, and reduced the interamolecular interaction caused by the increase ofinteramolecular distance. The conductivity of nanocomposite decreased, resulting inphotocurrent reduced. On the other hand, from the perspective of energy level, it can beseen from the linear sweep voltammetry curves （LSV）, The flat band voltage （LUMOlevel） of SDBS/PPy/TiO₂and MO/PPy/TiO₂composites are-0.65V and-0.60V. Theband gap of the SDBS/PPy is more narrow, therefore more excited electrons into theconduction band of polypyrrole to form photocurrent.