Development of sodium titanate semiconductor for removal of organic dyes from aqueous solutions and hydrogen production using photoelectrochemical (PEC) water splitting

Abstract

The widespread presence of organic dyes in industrial waste- waters from the paper, textile and apparel industries results in substantial environmental contamination. Carcinogenic and toxic properties of dyes are harmful to human beings and aquatic life. Hence, the removal of dyes from waste- waters is of crucial importance. The photodegradation of pollutants has gained enormous popularity in the past several years. Degradation of pollutant by this method does not form the secondary toxic products and organic pollutants can be completely mineralized to relatively non-hazardous products (water and CO2). Another environment issue comes from emission of CO2 from combustion of fossil fuels to produce energy that resulted in the global warming and global climate change issues. Photoelectrochemical (PEC) water splitting using semiconductor as a photoelectrode is one of the most promising routes for clean production of hydrogen. Hydrogen is most attractive and cleanest solar chemical fuel that does not result in any carbon emission during its oxidation in a fuel cell. Sodium titanate have been widely used as photocatalyst because of its high chemical inertness, low cost, abundance, lack of toxicity, thermal stability, and their proper band edge position for both photoelectrochemical water splitting and photocatalytic degradation of dye pollutant. However, some drawbacks of this type of photocatalyst such as inefficient usage of solar light due to its wide bandgap, low crystallinity, and High recombination rate of photogenerated electron and holes need to be solved. This thesis examines the effect of 4 strategies (acidic treatment with the assistance of ultrasonic waves, loading of noble metal, heterojunction with visible semiconductor, and optimization of NaOH concentration) to improve the photocatalytic and photoelectrochemical activity of sodium titanate for efficient degradation of organic pollutant and hydrogen production.