Preparation And Properties Of Hemp Activated Carbon Supported ZnO/CuO Photocatalyst

As a promising semiconductor materials,ZnO has aroused tremendous interests for its advantages of non-toxicity,cost-effectiveness and single synthetic method.In addition,it is easy to manipulate the morphology,microstructure and thereby achieve superior catalytic performance of ZnO photocatalyst.The ZnO photocatalysts have been employed to degrade textile dye contaminants.Nonetheless,a high band gap and the rapid recombination of photogenetated electronehole pairs,potentially limits the wide application of ZnO photocatalysts.In addition to UV light（less than 5%of the sunlight）,ZnO photocatalysts exhibit little photocatalytic sensitivity to the other composition of the sunlight.In recent years,considerable attention has been focused on ZnO-based composite photocatalysts with high catalytic activity and low cost.In this paper,hemp stem activated carbon（HSAC）was prepared by calcination method.ZnO/HSAC and ZnO/CuO/HSAC nanocomposite photocatalysts were prepared by hydrothermal method using HSAC as the carrier.The phase,morphology,specific surface area,functional groups,optical properties,photocatalytic activity and active groups were characterizated by XRD,SEM,BET,FTIR,UV-Vis and capturing experiment.The catalyst with three-dimensional flower-like morphology was obtained by controlling the mole ratio of ZnO to HSAC.The heterojunction of ZnO/CuO was prepared by introducing CuO.The effects of different CuO and HSAC dosage on photocatalytic performance were investigated.The synergistic photocatalytic mechanisms of"ZnO-HSAC"and"ZnO-CuO-HSAC"was proposed.The results are as follows:（1）The HSAC calcination process of carbonization and activation respectively at 500℃and 700℃,respectively.The activated carbon with high porosity,high specific surface area（2634 m²/g）and rich functional groups offers a foundation for subsequent experiments.（2）Using HSAC as the support,ZnO/HSAC was prepared by hydrothermal method by controlling the molar ratio of ZnO and HSAC.The composite catalyst showed excellent photocatalytic performance.The cooperatively catalytic mechanism was also discussed.Due to the high specific surface area and porous of HSAC and the molar ratio of ZnO and HSAC three-dimensional morphology were successfully prepared.The catalyst has a large specific surface area,which leading to a strong adsorption capacity in the catalytic process.Zn-C-O bond was formed at the interface between ZnO and HSAC,which enhances electron transfer and reduces the separation efficiency of electron and hole and improves the catalytic efficiency.（3）The preparation process was investigated in terms of hydrothermal time and temperature.The results show that optimal hydrothermal condition was 160℃/12h.（4）The ZnO/CuO/HSAC nano-composite with three-dimensional morphology were prepared by hydrothermal method by controlling the mole amount of CuO.The heterostructure was formed by introducing CuO and ZnO.The optical band gap was obviously reduced.The composite catalyst showed excellent catalytic activity under UV and visible light.The catalyst exhibited excellent photocatalytic degradation performance and cyclic stability under the conditions of ultraviolet and visible light.The main role of HSAC was to act as a carrier material and increase the specific surface area of the composite.In addition,the band gap of the composite powder was slightly reduced,which promoted the photocatalysis.The sample with the best photocatalytic activity was ZnO:CuO:HSAC=1:0.4:0.6.After three times of cyclic degradation,the degradation rate remained above 90%.（5）Synergistic mechanism of"ZnO-CuO-HSAC"photocatalysis was proposed.The results of transient photocurrent show that the carrier generation is large and the compound efficiency is low in ZnO/CuO/HSAC photocatalytic process.The capture experiment shows that the active groups were h⁺,·OH and·O₂^-.The h⁺plays a leading role.In the synergistic mechanism of"ZnO-CuO-HSAC"photocatalyzation,the carrier recombination rate is low due to the formation of heterojunction of ZnO/CuO and the high electron transfer ability of HSAC.