Photoreduction of environmental contaminants such as nitrate and carbon dioxide into clean fuels has become a key strategy for mitigating global environmental challenges. In a study published in Frontiers of Chemical Science and Engineering, researchers from the University of Tehran present a high‑performance ternary heterojunction photocatalyst that integrates three distinct components: zero‑dimensional CuBi₂S₄ quantum dots (acting as a metal‑assisted sulfide perovskite co‑catalyst), three‑dimensional Al₂WO₆ double perovskite (the central oxide perovskite photocatalyst), and two‑dimensional Ti₃C₂ MXene (a non‑metallic co‑catalyst facilitating interfacial charge transfer).
The nanocomposite was synthesized via a multi‑step method combining hydrothermal treatment and solid‑state reaction. Comprehensive characterization using XRD, XPS, SEM, TEM, HRTEM, UV‑Vis/DRS, PL, and EIS confirmed the successful formation of a 0D/3D/2D Schottky/Z‑scheme heterojunction. The band gap of Al₂WO₆ (3.35 eV) was reduced to 2.2 eV after doping, significantly enhancing visible‑light absorption. Photoluminescence and photocurrent measurements demonstrated efficient charge separation and suppressed electron‑hole recombination.
Under optimized conditions (pH 3, 25 °C, 5 h reaction time, 1.0 g·L⁻¹ catalyst, 70 W Xe lamp with UV‑cutoff filter), the CuBi₂S₄/Al₂WO₆/Ti₃C₂ photocatalyst achieved a nitrate reduction efficiency of 80%, with nitrogen gas identified as the predominant reduction product (55% selectivity). For CO₂ reduction, the efficiency reached 70%, with methane displaying the highest generation rate of 13.87 mL·g⁻¹·h⁻¹ (619 μmol·g⁻¹·h⁻¹), corresponding to 50% selectivity. In photocatalytic water splitting, the composite demonstrated a hydrogen evolution rate of 16 mL·g⁻¹·h⁻¹ (714 μmol·g⁻¹·h⁻¹) with an efficiency of 60%.
The working mechanism involves a Z‑scheme charge transfer pathway combined with a Schottky junction. Under visible light, electrons of CuBi₂S₄ are excited and act as powerful reducers; meanwhile, Ti₃C₂ MXene with high electrical conductivity donates electrons through the Schottky junction to the valence band of Al₂WO₆, compensating electron deficiency and creating a positive hole (h⁺) on MXene. This synergistic Schottky/Z‑scheme mechanism effectively separates holes and electrons, enhancing photocatalytic redox reactions.
Reusability tests showed that the ternary photocatalyst retained its photocatalytic performance after five consecutive cycles, with only a slight decrease in efficiency, confirming its excellent structural stability and durability. Comparison with recently reported photocatalysts demonstrates the superior performance of this novel nanocomposite.
This work provides a sustainable strategy for environmental remediation and renewable fuel generation, offering a promising pathway for converting pollutants into valuable products under visible light.
DOI
10.1007/s11705-026-2642-x