Target-directed design of dual-functional Z-scheme AgIn5S8/SnS2 heterojunction for Pb(II) capture and photocatalytic reduction of Cr(VI): Performance and mechanism insight

Abstract Target-directed design and synthesis of dual-functional materials with superior adsorption for Pb(II) and photocatalytic activity for Cr(VI) reduction are challenging but of vital importance for heavy metal-laden wastewater remediation. In this work, dual-functional Z-scheme AgIn5S8/SnS2 heterojunctions were designed according to hard-soft acid-base theory and band structure matching, and were synthesized by simple hydrothermal reaction. The AgIn5S8/SnS2 has high adsorptive capacity for Pb(II) with almost 100% Pb(II) removal, and the adsorptive capacity of AgIn5S8/SnS2 for Pb(II) is about 5 and 3.3 times that of AgIn5S8 and SnS2, respectively. Moreover, AgIn5S8/SnS2 shows outstanding visible-light photocatalytic performance for Cr(VI) reduction with 96% reduction efficiency. The XPS analysis, Zeta potential, DFT calculation reveal that S atoms are dominant adsorption sites, and the adsorption of Pb(II) is more favorable on AgIn5S8(3 1 1)/SnS2(1 0 1) than SnS2(1 0 1) or AgIn5S8(3 1 1) due to the remarkable coordination of S atoms with Pb(II) and strong electrostatic attraction. Furthermore, the photocatalytic mechanism of Z-scheme AgIn5S8/SnS2 heterojunction for Cr(VI) reduction was identified and uncovered by experimental studies.