Fractional Thermal Reduction of CuInS2 Quantum Dot-Sensitized Bi2MoO6 Hierarchical Flowers on S-Doped Biochar for Dual Z-Scheme/Mott–Schottky Heterojunction Construction: A Strategy for Efficient Photocatalytic Biorefineries

Abstract

In this work, an S-doped biochar-supported CuInS2 quantum dot-sensitized Bi2MoO6 hierarchical flower (CIS@BMO@SL) was prepared using a bottom-up technique. The partial thermal reduction of CuInS2 quantum dot-sensitized Bi2MoO6 successfully fabricated a dual heterojunction, which is composed of CuInS2/Bi2MoO6 Z-scheme and Bi/Bi2MoO6 Mott–Schottky heterojunctions. The dual heterojunction was identified by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy. Under the synergistic effect of the dual heterojunction, the electronic kinetics was significantly improved. Furthermore, the charge transfer resistance was further reduced by S-doped biochar. Under visible light irradiation, an exceptional xylonic acid yield of 86.59% was realized by CIS@BMO@SL. In this photocatalytic system, all active oxidation species, namely, ·OH, 1O2, ·O2–, and h+, were beneficial for producing xylonic acid. The primary role of h+ in the photocatalytic system was demonstrated via a poisoning experiment. According to XPS, the poisoning experiment, and electron spin resonance, the generation of ·O2– reveals a Z-scheme heterojunction between CuInS2 and Bi2MoO6.