Selected photoactive metal sulfides for environmental cleansing

[Display omitted] •Synthetic routes of metal sulfide photocatalysts.•Modification strategies of metal sulfide photocatalysts.•Stability and reusability of metal sulfide photocatalysts.•Photocatalytic CO2 reduction, H2 production, and degradation of carcinogenic pollutants on metal sulfide photocatalysts.•Metal sulfide photocatalysts role in oxidation of gaseous pollutants. Owing to their fascinating properties, such as good selectivity, sensitivity, long life-times and suitable redox potentials, metal sulfides are now the photocatalysts of choice in clean energy production and environmental remediation. There are several points of concern with metal sulfides, however, such as their narrow band gaps, poor light-absorption competences and high rates of recombination of electrons and holes. The present review is focused on the various modifications and synthetic strategies that are underway to help overcome some of these concerns. The effects of crystal sizes, crystal facets, shapes, calcination and sacrificial agents on structural-property relationships, and factors such as tuning stability and recovery methods for metal sulfides are also described. Moreover, the photocatalytic potential of metal sulfides in hydrogen production, CO2 reduction, pollutant degradation and oxidation of volatile organic compounds is discussed. And, with respect to future perspectives, the proper preparation methods, optimized calcination temperatures, crystallinities, and active sites are believed to be crucial for good stability and resultant photoactivity. Lastly, the developments of microscopy and in-situ spectroscopic techniques that are being proposed for a comprehensive study of the active sites and the associated electronic states are presented.