Uncovering Photocatalytic Mechanisms of Al₂W₃O₁₂: From a Low-Positive Thermal Expansion Ceramic to an Efficient Visible-Light-Driven Photocatalyst

The development of high-performance visible-light photocatalysts is crucial for advancing environmental remediation technologies. Here, we demonstrate for the first time the successful application of oxygen-deficient Al2W3O12 nanopowders, valued for their low-positive thermal expansion, as efficient visible-light-driven photocatalysts. Synthesized through controlled thermal treatments, these materials were tested for photocatalytic activity by degrading tetracycline (TC) and 4-chlorophenol (4-CP) under visible-light radiation. Comprehensive mechanistic studies, including electron paramagnetic resonance (EPR) spin-trapping, electrochemical analysis, and reactive oxygen species (ROS) scavenging experiments, provide the first insights into the photocatalytic mechanisms of Al2W3O12, revealing that oxygen vacancies play a pivotal role by extending visible-light absorption, improving charge carrier separation and migration, and boosting ROS generation. Notably, electronic holes and hydroxyl radicals were identified as the dominant ROS in pollutant degradation. These findings expand the functional scope of Al2W3O12 in photocatalysis and establish a new approach for optimizing other tungstate-based materials, offering significant potential for environmental remediation and sustainable energy applications.