Microwave-Assisted Photocatalytic CO₂ Reduction Based On Bi₄TaO₈Cl

Photocatalytic conversion of CO₂ is an effective strategy to simultaneously address global warming and energy shortage.Among them,photocatalytic reduction of CO₂,using water as an electron dono,has important research significance.However,the conversion rate of CO₂photocatalytic reduction is limited by the extremely slow kinetics of water oxidation.The introduction of additional thermal field in photocatalysis is conducive to improving the CO₂conversion rate.However,conventional heating has the disadvantages in large thermal inertia,longer heating and cooling time,and poor product selectivity.The combination of microwave field and photocatalysis is expected to achieve more efficient CO₂ catalytic conversion,due to its advantages in small thermal inertia and instant-on-stop.Therefore,this work focuses on introducing an external microwave field instead of traditional thermal field in photocatalytic CO₂ reduction,and the exploration of a suitable material system for microwave-assisted CO₂photoreduction.Bismuth oxyhalides stand out for its visible light sensitivity and the suited valence band position with water oxidation.And CO₂ reduction based on photosynergistic microwave under this system is still rarely reported.Based on the representative bismuth oxyhalide-Bi₄Ta O₈Cl,this work constructed a microwave-photoresponsive catalyst and studied the structure-activity relationship between catalyst and CO₂ reduction,which is expected to provide a novel technical method for improving the photocatalytic conversion rate of CO₂.The specific research contents are as follows:（1）Study on microwave-assisted photocatalytic CO₂ reduction reaction of novel photocatalyst Bi₄Ta O₈Cl.A novel photocatalyst Bi₄Ta O₈Cl was prepared by molten salt method,and the photocatalytic reduction yield of CO₂ to CO by Bi₄Ta O₈Cl nanosheets under different microwave powers was studied.The results showed that the introduction of microwave had a promoting effect on the photocatalytic process,and the yield of CO at 700W power is 11.43times higher than that of photocatalysis alone.Comprehensive analysis showed that the external microwave field provided energy for the catalytic system,thereby improving the efficiency of photocatalytic CO₂ reduction over Bi₄Ta O₈Cl,because of the conversion of microwave energy into thermal energy.（2）Study on Bi₄Ta O₈Cl/W₁₈O₄₉ microwave-assisted photocatalytic CO₂ reduction reaction.We prepared a direct Z-scheme heterojunction over Bi₄Ta O₈Cl/W₁₈O₄₉ photocatalyst and deeply studied its microwave-assisted photocatalytic activity for CO₂ reduction.Compared with traditional thermal catalysis,the photocatalytic reduction yield of CO₂ to CH₄ increased by 103 times at 400 W,and the yield of CO₂ to CO increased by 54.12 times.Comprehensive analysis showed that the direct Z-type heterojunction significantly improved the utilization rate of photogenerated electrons on the Bi₄Ta O₈Cl side in the Bi₄Ta O₈Cl/W₁₈O₄₉ system.Moreover,microwave field provided thermal energy for the reaction,reduced the activation energy of the reaction and generated high-energy sites located on the surface,greatly increasing the surface reaction rate.In conclusion,microwave can enhance the efficiency of CO₂ reduction over Bi₄Ta O₈Cl-based photocatalysts,which provides an idea for the external field assistance of photocatalytic CO₂ reduction by bismuth halogenoxide system materials.