Coordination between semiconductor defects and their role in charge separation and light absorption for exceptional solar light driven photocatalysis

To address energy and environmental issues, effective and efficient photocatalysis is believed to be the real elevator. However, currently low solar light absorption, extended charge recombination and ineffective adsorption of the reacting species largely hindered the efficiency of semiconductor photocatalysis. Defect engineering is becoming an effective tool to improve solar light absorption, extend charge separation and accelerate adsorption of the reacting species on the surface of photocatalysts. In this review article, we have discussed classification of defects, and the various techniques such as X-ray photoelectron microscopy, X-Ray diffractometry, transmission electron microscopy, Raman, positron annihilation, and photoluminescence spectroscopy used for their measurement in detail. We have thrown a bird eye view on the photocatalytic processes, light absorption and charge separation. We have also discussed in detail the coordination and role of different defects in improving light absorption, charge separation and surface activation for effective photocatalysis. Further, we have also highlighted the role of different defects in various semiconductors for the photocatalytic hydrogen generation from water. Finally, we have discussed future perspectives and research gap in the defective photocatalysis. We believe that this review article will significantly attract massive research towards photocatalysis with defective semiconductors for energy generation and environmental purification.