4. Metal and Non-metal Doped Metal Oxides and Sulfides

Increasing demand of clean energy, growth in global population, and tremendous global warming necessitate sustainable energy production. Photochemistry or photocatalysis using semiconductor is one direct way of converting solar light into fuel without CO₂ emission. Use of cheap and renewable energy sources like sunlight and water is an efficient way toward green energy generation. Semiconductors like metal oxides and metal sulfides are materials of interest for photocatalysis because of their good optical and electronic properties. However, most of the semiconductors do not have suitable band alignment to absorb sunlight efficiently. In this line, use of metal oxides and sulfides can be an advantageous strategy for desirable band tuning for visible light photocatalysis. In this chapter, we present highlights on metal- and nonmetal-doped metal oxides and sulfides for photocatalysis.

Photocatalysis is an important field for hydrogen production, environment remediation, and electronic manufacturing. Since the introduction of TiO₂ as photocatalyst in the late 1960s by Honda and Fujishima, many other semiconductors gained attention due to their good optical, electronic, and photocatalytic properties. To absorb whole solar spectrum, proper VB and CB alignment with respect to water oxidation and reduction potential, respectively, is required for photocatalysis. All semiconductors do not have suitable band gap and band alignment to exhibit efficient or visible light photocatalysis. Metal and nonmetal doping of semiconductors like metal oxides and sulfides can be an effective strategy to push the band gap in the optimum region to be suitable for overall photocatalysis. The present chapter is an attempt to provide a detailed description of various aspects for the development of suitable photocatalyst, i.e., preferred band gap materials, metal doping, nonmetal doping, and challenges associated with them like broad absorption capability and low recombination probability.