PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS FROM WATER

Abstract

Solar energy harvesting through semiconductor-based photocatalysts has emerged as a promising approach for applications such as solar power generation, water splitting, and the degradation of waterborne pollutants. Photocatalysis operates on the principle of photon-induced excitation of electrons from the valence band (Ev) to the conduction band (Ec) when the incident photon energy (hν) equals or exceeds the band gap energy (Eg) of the material. The generated electron-hole pairs (e⁻/h⁺) act as strong reducing and oxidizing agents, respectively. While many photocatalysts effectively absorb ultraviolet (UV) light (~390 nm), this only represents a small fraction (~5%) of the solar spectrum. Therefore, significant research is being directed toward extending photocatalytic activity into the visible spectrum (400–750 nm) through strategies such as metal/nonmetal doping, spectral sensitization with dyes or polymers, and the use of narrow-band-gap semiconductors as photosensitizers. However, the efficiency of photocatalysis is often limited by factors such as nanoparticle aggregation and charge carrier recombination. The formation of mesoporous structures and enhanced charge separation/migration have shown promise in overcoming these limitations and improving photocatalytic performance. This work reviews the fundamental mechanisms and current advancements in semiconductor-based photocatalysis aimed at enhancing solar energy utilization.