Surface modifications, perspectives, and challenges of scheelite metal molybdate photocatalysts for removal of organic pollutants in wastewater

Abstract Semiconductor-mediated photocatalysis is a promising green technology which has been widely adopted for solving energy and environmental issues. Among the semiconductor photocatalysts, the scheelite tetragonal structure of metal molybdate materials have attracted tremendous research attention in the application for photocatalytic degradation of organic pollutants due to their diverse band gaps, unique physical and chemical properties, ecofriendly characters, abundant sources of molybdenum (Mo) element, and low cost. However, the fast recombination of photogenerated electron-hole pairs results in decreased efficiency of the photocatalysis. Thus, this review covers the progresses in various unmodified and modified scheelite metal molybdate photocatalysts, which include PbMoO4, BaMoO4, CaMoO4, SrMoO4, and CdMoO4. The modification methods are categorized into morphology control, facet modification, doped, plasmonic, and heterojunction, which are devoted to the degradation of organic pollutants (mostly, dyes and drugs) and to overcome the rapid recombination of electron-hole pairs. Furthermore, the challenges and future direction as well as the perspectives toward the designation for more efficient scheelite metal molybdate photocatalysts are discussed through extensive literature review.