K.T. Ranjit

Bio: K.T. Ranjit is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Nitrite & Nitrate. The author has an hindex of 8, co-authored 9 publications receiving 583 citations.

Synthesis, characterization and photocatalytic properties of iron-doped TiO2 catalysts

Abstract: Fe-doped TiO2 catalysts were prepared by coprecipitation and the sol-gel method. The anatase to rutile phase transformation is dependent on the nature of the precursor used. Sol-gel-derived iron-doped catalysts show the presence of rutile and pseudobrookite phases, whereas coprecipitated catalysts show only the anatase phase. The role of the dopant ion is primarily to improve the charge separation of the photoproduced electron-hole pairs via a permanent electric field. The photocatalytic activity of the iron-doped catalysts can be explained in terms of the heterojunction formed between the Fe/TiO2 and α-Fe2O3 phases for the sol-gel-derived catalyst.

Photocatalytic reduction of dinitrogen to ammonia over noble-metal-loaded TiO2

Abstract: The photocatalytic reduction of dinitrogen to ammonia is influenced by the nature and amount of metal loading on TiO2. The optimum metal content varies depending on the nature of the metal. A correlation between the ammonia yield and the intermediary MH bond strength is established (low bond strength gives rise to low ammonia yield).

Photocatalytic reduction of nitrite and nitrate ions to ammonia on M/TiO2 catalysts

Abstract: Noble metal loaded TiO2 catalysts have been employed as catalysts for the photocatalytic reduction of nitrite and nitrate ions to ammonia. The yield of ammonia was found to depend on the nature, amount of metal and the method of metallization. An optimum metal content is beneficial for the activity. Beyond the optimum content the activity decreases.

Photocatalytic reduction of nitrite and nitrate ions over doped TiO2 catalysts

Abstract: Doping of TiO 2 with altervalent cations, Fe 3+ , Cr 3+ , Co 2+ and Mg 2+ leads to a red shift in the onset of absorption. The role of the dopant ions is primarily to improve the charge separation by means of a permanent electric field. Doping of TiO 2 also influences the adsorption of reagent species and the resulting photoactivity is a consequence of these two factors. An optimum level of dopant ions is beneficial for the photocatalytic activity of TiO 2 .

Photocatalytic reduction of nitrite and nitrate on ZnS

Abstract: The photocatalytic reduction of nitrite and nitrate to ammonia was tested on ZnS. The yield of ammonia was found to depend on the precursor used for the preparation of ZnS, the temperature of pre-treatment, the sacrificial agent, the pH, the time of irradiation and the nature of metal loaded on ZnS.

Photoelectrocatalytic materials for environmental applications

Abstract: This feature article summarizes recent research on and development of semiconductor-based photocatalyst materials that are applicable to environmental remediation and/or chemical synthesis purposes. A wide variety of TiO2 particles and/or films have been studied during the past 30 years because they are the most stable and powerful photocatalysts leading to the degradation of various organic pollutants. The photocatalytic performance of other semiconductor materials such as ZnO, SnO2, WO3, Fe2O3 and CdS has also been intensively investigated. A general limitation in the efficiency of any photocatalytic process is the recombination of the photogenerated charge carriers, i.e., of electrons and holes, following bandgap illumination. Considerable efforts have been made to suppress this recombination and hence to enhance the charge carrier separation and the overall efficiency by means of coupling of different semiconductors with desirable matching of their electronic band structures, or incorporation of noble metal nanoclusters onto the surface of semiconductor photocatalyst particles. Modification of the physicochemical properties, such as particle size, surface area, porosity and/or crystallinity of the semiconductor materials, and optimization of the experimental conditions, such as pH, illumination conditions and/or catalyst loading, during photocatalytic reactions have also been carefully addressed to achieve high reaction rates or yields. To utilize solar energy more efficiently, i.e., to extend the optical absorption of the mostly UV-sensitive photocatalysts into the visible light range, numerous research groups have contributed to the development of novel visible light active photocatalysts. With the application of semiconductors with narrower bandgaps such as CdS, Fe2O3 and WO3 being straightforward choices, doping of wide bandgap semiconductors like TiO2 has been the most popular technique to enhance the catalysts' optical absorption abilities. Research on mixed-oxide-based semiconductor photocatalysts with deliberately modulated band structures has also attracted tremendous attention in the past decade, concentrating on, for example, the generation of H2 and/or O2 from H2O splitting, and the degradation of organic pollutants under visible light irradiation. Both theoretical calculations and experimental results have convincingly shown that the developed materials can serve as highly efficient photocatalysts that are both environmentally and economically significant.