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

• Dual-functional Z-scheme AgIn 5 S 8 /SnS 2 heterojunction was target-directed designed. • AgIn 5 S 8 /SnS 2 has high adsorption capacity for Pb(II) capture. • AgIn 5 S 8 /SnS 2 shows superior photocatalytic activity for Cr(VI) reduction. • Pb(II) adsorption was attributed to S-Pb coordination and electrostatic attraction. • Z-scheme photocatalytic mechanism was based on internal electric field. 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 AgIn 5 S 8 /SnS 2 heterojunctions were designed according to hard-soft acid-base theory and band structure matching, and were synthesized by simple hydrothermal reaction. The AgIn 5 S 8 /SnS 2 has high adsorptive capacity for Pb(II) with almost 100% Pb(II) removal, and the adsorptive capacity of AgIn 5 S 8 /SnS 2 for Pb(II) is about 5 and 3.3 times that of AgIn 5 S 8 and SnS 2 , respectively. Moreover, AgIn 5 S 8 /SnS 2 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 AgIn 5 S 8 (3 1 1)/SnS 2 (1 0 1) than SnS 2 (1 0 1) or AgIn 5 S 8 (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 AgIn 5 S 8 /SnS 2 heterojunction for Cr(VI) reduction was identified and uncovered by experimental studies.