Organic pollutant degradation over highly efficient Mn-Mo(O,S)2 oxysulfide photocatalyst under visible light illumination

Abstract

Metal oxide semiconductor photocatalysts have received remarkable consideration as a promising technology for environmental remediation and energy conversion. Oxysulfide semiconductors have narrow band gaps which are appropriate for photocatalytic removal of toxic organic pollutants under visible light illumination. For the elimination purpose of these pollutants, Mo(O,S)2, Mn(O,S)2, and Mn-Mo(O,S)2 oxysulfide catalysts containing various Mn contents were synthesized at low temperatures via a simple method. The structural, morphological, electrochemical, compositional, and optical properties of the as-synthesized catalysts were exhaustively characterized. The photocatalytic degradation activity of the bares Mo(O,S)2, Mn(O,S)2, and other Mn-Mo(O,S)2 compositions were evaluated over different types of organic pollutants under visible light illumination. The addition of Mn in Mo(O,S)2 structure improved the photodegradation activity, and Mn-Mo(O,S)2-30 was found to be the best composition with superior photodegradation performance towards the four cationic, anionic, and neutral dyes. The degradation efficiency of 10 ppm of MB, and MO dyes reach 99.7% and 98.6%, within 30 and 120 min, respectively. Mn-Mo(O,S)2-30 catalyst also shows a good photodegradation performance on Rh B and NR organic pollutants. According to the recycling test, the catalyst exhibited excellent performance. The photodegradation follows pseudo-first order kinetics with a rate constant of 0.097 and 0.036 min-1 for MB and MO dyes, respectively. The trapping experiment showed that superoxide anion radicals (O2•-) and holes (h+) are the responsible active species for the degradation on MO and MB, respectively. The novelty of usingMn-Mo(O,S)2-30 for various dyes degradation lies in its remarkable catalytic properties.