Lignin‐Derived Carbon Quantum Dots as Hole‐Trapping Promoters in LCDs/Bi‐MOF/ZIS With S‐Scheme Heterojunction for Efficient Photocatalytic Hydrogen Peroxide Production in Pure Water

ABSTRACT

Photocatalytic hydrogen peroxide (H ₂ O ₂ ) production from water and oxygen driven by solar energy represents a highly promising green and sustainable strategy. Herein, lignin‐derived carbon quantum dots (LCDs) were strategically introduced at the heterojunction between a Bi‐based metal organic framework (Bi‐MOF) and ZnIn ₂ S ₄ (ZIS). Under visible‐light irradiation ( λ  ≥ 420 nm) in pure water, the optimized LCDs/Bi‐MOF/ZIS photocatalyst achieves a remarkable H ₂ O ₂ production rate of 2763.04 μmol g ⁻¹  h ⁻¹ , and exhibits only a ca. 1.9% decline after five consecutive cycles. The in‐situ x‐ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed that the rapid migration of photogenerated carriers via the S‐scheme pathway from Bi‐MOF to ZIS substantially improved light harvesting efficiency and prolonged the lifetime of active electrons. Meanwhile, the role of LCDs as efficient hole scavengers was confirmed by transient photovoltage (TPV) measurements, which demonstrated their ability to extract photogenerated holes and effectively suppress charge‐hole recombination. Consequently, the proposed mechanism for H ₂ O ₂ production through the two‐electron oxygen reduction reaction (2e ⁻ ORR) conversion was confirmed by in‐situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and DFT calculations. Accordingly, the hole‐trapping engineering of S‐scheme photocatalysts offers an innovative strategy toward high‐efficiency photocatalytic H ₂ O ₂ evolution.