阴极辉光放电电解制备纳米ZnO

Synthesis of ZnO Nanoparticles by Cathode Glow Discharge Electrolysis

以Pt针为阴极,Zn片为阳极,2 g/L Na_(2)SO_(4)溶液为电解质,在530~650 V放电电压下,利用阴极辉光放电电解(CGDE)技术一步制得纳米ZnO颗粒。用XRD、SEM、FTIR、XPS等对产物的结构、组成和形貌进行了表征,利用UV-Vis DRS计算了纳米ZnO颗粒的带隙能,用UV-Vis研究了纳米ZnO粒子光催化降解亚甲基蓝(MB)的行为,并探讨了其制备机理。结果表明,580 V下得到的纳米ZnO颗粒有一定的团聚,加入表面活性剂聚乙烯吡咯烷酮(PVP)能够抑制纳米ZnO颗粒的团聚;材料的形貌随PVP浓度和放电电压的变化而变化。当电压为530 V、加入0.0031%(质量分数)的PVP时,得到尺寸约200 nm、带隙能为3.22 eV的纺锤状纳米ZnO;随电压升高,颗粒尺寸分布越宽。在紫外光照射30 min后,加入PVP所制备的ZnO光催化降解MB的降解率由78.5%提高到87.3%,说明加入PVP后制备的ZnO光催化性能更优。CGDE制备纳米ZnO的机理为:放电过程中阳极Zn片氧化溶解为Zn^(2+),然后Zn^(2+)迁移到阴极辉光区,与等离子体-液体界面产生的OH-反应生成[Zn(OH)_(4)]^(2-),最后[Zn(OH)_(4)]^(2-)从等离子体-液体界面区转移到溶液中,产生ZnO晶粒。

In this work,ZnO nanoparticles(ZnO NPs)were prepared by one-step method using cathode glow discharge electrolysis(CGDE)in 2.0 g/L Na_(2)SO_(4)solution at 530—650 V discharge voltage,in which Zn foil and Pt needle point were served as anode and cathode,respectively.The structure,component and morphology of ZnO NPs were characterized by XRD,SEM,FTIR and XPS.The band gap energy of ZnO NPs was calculated based on UV-Vis DRS.The photocatalytic property of ZnO NPs for the degradation of MB was investigated by using UV-Vis.A possible preparation mechanism of ZnO NPs under CGDE was also proposed.The results showed that the ZnO NPs prepared at 580 V have a certain agglomeration,and adding PVP can reduce the agglomeration.The morphology of ZnO NPs is changed with the concentration of PVP and the applied voltage.At 530 V applied voltage and adding 0.0031%PVP,spindle ZnO NPs with particle sizes of about 200 nm and band gap of 3.22 eV are successfully prepared by CGDE.Meanwhile,the particle size distribution widens with the increase of voltage.After 30 min UV irradiation,the degradation rate of ZnO with PVP increases from 78.5%to 87.3%,indicating that the photocatalytic property of ZnO NPs with PVP is markedly superior to that of ZnO NPs without adding PVP.The synthesis mechanism of ZnO NPs by CGDE is as follows:the anode Zn foil is oxidized to produce Zn^(2+),and then migrate to the cathode glow discharge region.After that,[Zn(OH)_(4)]^(2-)is generated by the reaction with the OH-produced in the plasma region and Zn^(2+).Finally,[Zn(OH)_(4)]^(2-)is transferred from the plasmas-liquid interface into the solution to form ZnO NPs.