Away from TiO2: A critical minireview on the developing of new photocatalysts for degradation of contaminants in water

During recent years there has been a growing tendency to study new photocatalysts for water and air treatment. To large extent this endeavor is part of a more general effort searching for efficient conversion of solar energy into electricity and into chemical energy stored in hydrogen. Yet, despite the so many man-years invested in this search titanium dioxide is still considered to be the photocatalyst of choice. This paper discusses the current status of research with non-TiO2 photocatalysts for water decontamination. It suggests that developing of new, highly photoactive photocatalysts for water and air treatment is hindered by a combination of reasons, reflecting the tendency of the scientific community to “search under the streetlight”. This includes the overemphasis on bandgap values while overlooking the importance of band positions, the use of dyes as model contaminants under visible light, the ignoring of the importance of transient phenomena, the under-emphasis of the role of surface area and the lack of implementation of theoretical tools in the developing of new photocatalysts. Stepping out of the comfort zone is not only possible but essential.