Surface Modification of TiO2 and WO3 with Platinum and Inorganic Anions for Enhancing Photocatalytic Activities

Abstract

This study investigated surface modification of metal oxide semiconductors (TiO2 and WO3) for enhancing photocatalytic activities on the degradation of pollutant and production of hydrogen. Since a realistic possibility for practical applications of photocatalyst was introduced in 1972, many studies on its applications (e.g., environmental remediation and renewable energy production) have been tried in many ways. For the practical applications of photocatalyst, many fields of study (e.g., material synthesis and modification, reaction kinetic and mechanism, reactor design, thin film and coating fabrication, theoretical (computational) chemistry, analytical chemistry, and surface chemistry) should be developed together. Among them, surface modification of photocatalyst is very important to improve photocatalytic efficiency and achieve practical applications because the photocatalytic reaction and efficiency greatly depend on the surface property of photocatalyst. In this work, surface-modified photocatalyst was developed for higher photocatalytic activities and dual-purpose photocatalysis (i.e., simultaneous production of hydrogen and degradation of water pollutants). The dual-purpose photocatalytic process is conceptually compared with biological methods that recover energy from wastewater such as microbial fuel cells and anaerobic digestion with methane production, but little investigated so far. In the first work, TiO2 was simultaneously modified with fluoride and platinum for the anoxic degradation of organic compounds. In the second work, the simultaneous production of hydrogen and degradation of organic pollutants was achieved by modifying the surface of titania with fluorides and platinum nanoparticles on the basis of the first work. In third work, TiO2 was simultaneously modified with phosphate and platinum to overcome the problem on pH stablility which is raised in simultaneously surface fluorinated and platinized TiO2. In fourth work, the oxidative reaction mechanism occurring on surface-modified visible photocatalyst (platinized WO3) and the role of main oxidants were investigated.