PHOTOELECTROCATALYTIC ACTIVITY OF In(III)-MODIFIED TiO2 PHOTOANODES IN THE VISIBLE SPECTRUM REGION

Nanocrystalline film photoanodes of titanium dioxide modified with In(III) ions in the concentration from 1.0 to 10 mass.% (0.23 to 2.52 at%, respectively) are manufactured using the sol-gel method. Their physicochemical characteristics and structure of In - containing compounds on the TiO2 surface are investigated by transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis absorption spectroscopy. The photoelectrocatalytic activity of these anodes in the reactions of methanol and formic acid electrooxidation studied under illumination with monochromatic light (369 and 461 nm; 7.5 and 10 mW cm-2, respectively) and visible light (sunlight simulator; 100 mW cm-2) is shown to decrease symbatically with an increase in indium content. It is also shown that a selective photoelectrooxidation of methanol is observed for titanium dioxide modified with 0.23 at.% In in a potential region of (-780 ÷ -550 mV). Using the photocurrent modulation spectroscopy (IMPS), the recombination rate constants and the charge carrier transfer efficiency are determined under illumination of the modified photoanode with monochromatic light (369 nm; 7.5 mW cm-2) at a potential of -0.8 V in a solution of 0.1 M KOH in the methanol presence. It is demonstrated that doping of titanium dioxide with 0.23 at.% In promotes both an increase in the current of electron – hole pairs generation and a decrease in recombination losses.