Advanced oxidation processes via semiconductor photocatalysis for water treatment have been the subject of extensive research over the past three decades, producing many scientific reports focused on elucidating mechanisms and enhancing kinetics for the treatment of contaminants in water. Many of these reports imply that the ultimate goal of the research is to apply photocatalysis in municipal water treatment operations. However, this ignores immense technology transfer problems, perpetuating a widening gap between academic advocation and industrial application. In this Feature, we undertake a critical examination of the trajectory of photocatalytic water treatment research, assessing the viability of proposed applications and identifying those with the most promising future. Several strategies are proposed for scientists and engineers who aim to support research efforts to bring industrially relevant photocatalytic water treatment processes to fruition. Although the reassessed potential may not live up to initial academic hype, an unfavorable assessment in some areas does not preclude the transfer of photocatalysis for water treatment to other niche applications as the technology retains substantive and unique benefits.

Graphene oxide modified g-C₃N₄ (GO/g-C₃N₄) with efficient photocatalytic capability under visible light irradiation was fabricated by sonochemical approach. Transmission electron microscopy images demonstrated that GO was two-dimensional sheets with chiffon-like ripples and the g-C₃N₄ possessed a layered structure. GO was overlaid on the surface of g-C₃N₄ in the GO/g-C₃N₄ hybrids. The UV–vis diffuse reflectance spectra showed that the GO/g-C₃N₄ hybrid had intense optical absorption in the visible light region. Photoluminescence spectra confirmed that the separation efficiency of photogenerated charge in GO/g-C₃N₄ was more intensive than pristine g-C₃N₄, indicating the GO acts as a separation centre and electron acceptor in the GO/g-C₃N₄ hybrid. The effective photogenerated charge separation efficiency lead to a remarkable improvement in the visible light photocatalysis. The pseudo-first-order kinetic constants of photocatalytic degradation of rhodamine B and 2, 4-dichlorophenol under visible light irradiation with GO/g-C₃N₄ were 3.80 and 2.08 times as large as that with pristine g-C₃N₄, respectively. This work indicates that the metal-free GO/g-C₃N₄ hybrid photocatalyst is a promising material in waste control, and GO could be an excellent material to combine with other semiconductors to make composites.