Mn2+ doped AgInS2 photocatalyst for formaldehyde degradation and hydrogen production from water splitting by carbon tube enhancement

In this work, AgInS2 and Mn2+ doped AgInS2 (Mn–AgInS2) with different Mn2+: (Ag+ + In3+) ratios were synthesized via a low temperature liquid method. The photocatalytic activity of the obtained samples was followed by taking formaldehyde as the target pollutant under visible light irradiation. The photocatalysts were passed through various characterization procedures to investigate their morphological, structural and photophysical characteristics. The optimal proportion sample [with the ratio n (Mn2+): n (Ag+ + In3+) = 1:100] photodegraded about 79% formaldehyde in 150 min. These upgraded activities are attributed to the enhanced visible light absorption and superior charge separation due to the presence of Mn2+ as confirmed site from charge separation measurements. In addition, a possible mechanism for the photodegradation of formaldehyde is proposed based on the experimental results. Furthermore, the photocatalytic water splitting performance of Mn–AgInS2 and multi-walled carbon nanotubes (MWCNTs) modified Mn–AgInS2 is investigated and compared under simulated sunlight irradiation, and remarkable hydrogen production is achieved (105 μmol h−1 g−1) by using the latter.