Cation-modified photocatalysts

Abstract Photocatalyst modification with cationic ions has been proven as a versatile technology to enhance the photocatalytic activity. This improvement can be attributed to factors, such as (i) the introduction of new defect states into the band gap, which can reduce the electron–hole recombination and shift the absorption from UV to visible-light wavelengths, (ii) the plasmonic effect of noble metals, and (iii) the visible-light response due to the f–f transitions of rare earths. Different methods are currently used to include cationic ions on the photocatalysts’ surface, such as solvothermal, microemulsion, hydrothermal, microwave, chemical precipitation, photoreduction, and sol–gel. Besides, depending on the ionic radius of the dopant, the concentration, and the doping method, these dopants can be incorporated in substitutional or interstitial positions into photocatalyst lattice or can be found as highly dispersed metal oxide clusters.