煅烧温度对阳极氧化WO3多孔薄膜的形貌及光电化学性能的影响

采用一步式阶跃电压加压方法,在NH4F/(NH4)2SO4电解质溶液中对W片进行阳极氧化处理制备了WO3多孔薄膜,通过后续热处理温度的控制,制备了性能规律性变化的WO3多孔纳米薄膜材料.用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)分析等手段考察了热处理温度对氧化钨晶体结构和形貌影响的规律,在450°C以下的煅烧温度下,薄膜保持50-100nm孔径;通过对光电化学性质、光催化降解甲基橙动力学行为的研究,考察了不同热处理温度对WO3多孔薄膜光电转换性能影响的规律.研究表明,450°C煅烧处理后的WO3薄膜在500W氙灯光源照射及1.2V偏压下,光电流密度达到5.11mA·cm-2;340及400nm单色光辐射下光电转换效率(IPCE)值分别达到87.4%及22.1%.电化学交流阻抗谱显示,450°C煅烧处理后的WO3薄膜表现出最佳的导电率及最小的界面电荷转移电阻.实验结果证明,高结晶度的多孔结构是WO3薄膜具有高光电转换效率的主要因素,控制热处理温度是实现薄膜具有高孔隙率、完整结晶度、低电阻的重要手段.

Effects of Calcination Temperature on Morphologies and Photoelectrochemical Properties of Anodized WO3 Nanoporous Films

Visible-light-responsive WO3 porous films were synthesized via step-voltage anodization in NH4F/(NH4)2SO4 solution and calcined at various temperatures.The crystalline phase and surface morphology were characterized using X-ray diffraction(XRD)and field emission scanning electron microscopy(FE-SEM).The as-anodized nanoporous films converted to a monoclinic phase with preferential orientation in the(020)planes,and the pore diameters of the films calcined below 450°C were estimated to be in the region of 50-100 nm.The photocatalytic activity was evaluated via photodegradation of methyl orange.The film calcined at 450°C showed the highest photocatalytic activity.Photoelectrochemical measurements showed that the incident photon-to-current conversion efficiency(IPCE)values of the film calcined at 450°C were 87.4%at 340 nm and 22.1%at 400 nm.Under visible light(λ≥400 nm),the photocurrent density in 0.5mo·lL-1 H2SO4 solution at 1.2V(vs Ag/AgCl(KCl saturated))was 5.11 mA·cm -2 . Electrochemical impedance spectroscopy(EIS)measurements showed that the film calcined at 450°C exhibited the smallest interface charge transfer resistance and optimal electroconductivity.Perfect crystallinity,high porosity and low resistance can therefore be obtained by controlling the calcination temperature.A large surface area and a porous structure are important factors in affecting photocatalytic activity.