Controllable fabrication of α-Ag2WO4 nanorod-clusters with superior simulated sunlight photocatalytic performance

Abstract

α-Ag₂WO₄ clusters comprising an assembly of nanorods were controllably fabricated via a simple ion exchange method at room temperature. The phase, morphology, microstructure, optical absorption, photoluminescence, photoelectrochemical properties and photocatalytic behavior of the products were systematically explored. α-Ag₂WO₄ nanorod-clusters of high purity are achieved at a medium pH of 9.8 provided by adjusting the molar ratio of AgNO₃ and Na₂WO₄ to 1 : 4, and the sample exhibits superior photocatalytic activity for the degradation of organic pollutants. Its rate constant k is as high as 21.8 fold in comparison with that of the sample obtained with stoichiometric raw materials at a ratio of 1 : 0.5. The boosted photoactivity of α-Ag₂WO₄ clusters can be well accounted for by the broadened light harvesting and accelerated charge separation, which are proved by the red-shifted light absorption, higher photocurrent and a smaller Nyquist impedance radius. Based on the detected active species and the band edge positions, a possible migration mechanism of photoinduced e⁻/h⁺ pairs on the surface of α-Ag₂WO₄ clusters was proposed. This work provides some new insights into the rational design and synthesis of photocatalysts with a deep understanding of the relationship among the experimental parameters, the microstructure and properties to acquire a more desired photoactivity.