Microwave-mechanochemistry-assisted synthesis of Z-scheme HSr2Nb3O10/WO3 heterojunctions for improved simulated sunlight driven photocatalytic activity

Abstract To shorten the preparation time, in this study, we developed a simulated sunlight driven 2D/2D HSr2Nb3O10/WO3 composite with noteworthy photocatalytic activities for degrading methyl orange (MO). The HSr2Nb3O10/WO3 composites were prepared by planetary ball milling of WO3 nanosheets with HSr2Nb3O10 nanosheets. The ultrathin HSr2Nb3O10 nanosheets were synthesized by an ion-exchange reaction with the assistant of microwave irradiation in a sharply reduced time compared to the conventional method. The as-prepared HSr2Nb3O10/WO3 composites exhibited superior photocatalytic performance than those of pristine HSr2Nb3O10 and WO3. The best photocatalysts HSNO-ns/PWO7 composite showed the degradation rate of ca. 99.7 % for MO within only 25 min under the simulated sunlight irradiation. The enhancement of photocurrents and photocatalytic activity could be attributed to the simultaneous improvement of photon absorption and photo-induced charge separation and migration. The result clearly indicated that the heterojunction was constructed successfully by the high energy mechanochemical reaction. The excellent heterojunction interaction between HSr2Nb3O10 and WO3 could be corroborated by the photoelectrochemical analysis and electrochemical impedance spectroscopy. A Z-Scheme photocatalytic mechanism was proposed based on the theory and the radical species trapping experiments.