NOVEL LAYERED TITANATES AND NIOBATES: APPLICATIONS IN PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS AND WATER SPLITTING

Abstract

Extensive industrialization and rapid population growth with decreasing groundwater at alarming rates make it challenging to access limited clean water resources. Due to incomplete treatment of industrial effluents, frequent use of antibiotics and personal care products, various organic pollutants have emerged to persist in the municipal wastewater that ultimately gets into the drinking water system untreated. On the other hand, the global energy demands are rising due to high growth rate of urbanization and industrial expansion, which are some of the greatest challenges of this century. As most of the global energy needs are fulfilled by fossil fuels, which is the main cause of global warming, energy generation from alternative renewable resources become indispensable. The solar energy reaching the Earth's atmosphere every hour is far beyond the annual energy demand of the whole world. It is abundant, free of cost and clean source of energy. After the discovery of water-photolysis on TiO2 semiconductor electrode by Fujishima-Honda in 1972, vast majority of research has been devoted on semiconductor photocatalysis that continues to grow even today, although the use of TiO2 and many other oxide semiconductors under solar irradiation is limited because of their UV active nature. Considering the abundance of ‘visible light’ amounting to ~ 43% of incoming solar energy, a lot of research efforts in the global arena have been devoted toward the development of visible-light-active photocatalysts for efficient utilization of solar energy. Semiconductor photocatalysis for degradation of harmful organic pollutants and hydrogen production from water renders a sustainable solution toward use and generation of renewable energy. Use of sunlight in semiconductor photocatalysis for pollutant degradation or wastewater treatment can avoid use of chemical reagents and electrical energy inputs. Ideally, an efficient sunlight-driven photocatalyst can find niche applications in some of the emergent areas of energy and environment.