Effect of Structural Parameters of TiO2 Nanotube Arrays upon Their Photocatalytic/Photoelectrocatalytic Performance

The effect of structural parameters of TiO₂ nanotube arrays (TNAs) upon their photocatalytic/photoelectro‐catalytic performance is studied by comparing the morphological characteristics and physicochemical properties with different tube lengths prepared from three kinds of electrolytes. The results show that the UV‐Vis absorption edge of TNAs red‐shifted with the increment of tube length and the short TNAs possess higher bandgap energy. The variation tendency of electrochemical window of TNAs is DMSO (5.5 V)>Cit (3.2 V)>HF (1.8 V). The long TNAs possess higher photocatalytic (PC) reactivity suggesting the surface roughness factor is the main determinant of PC efficiency, although, there is obvious recombination effects for the long TNAs. Evidenced by the positive correlation between tube length and photoelectrocatalytic (PEC) efficiency for TNAs from the same electrolyte, the enhancement of the tube length could lead to better PEC reactivity, but when the tube length is over a certain value, the PEC degradation rate no longer increases but decreases. The long TNAs with large surface roughness factor prepared from Cit and DMSO electrolytes exhibit comparative or even lower PEC performance compared with the short TNAs prepared from HF electrolyte, indicating that the PEC performance of TNAs was dominated by charge separation and photoelectron transfer properties rather than surface roughness coefficient and the tube length.     

纳米TiO_2薄膜电极光电催化降解染料RhB的研究

利用光电协同作用可增强TiO2光催化氧化的量子效率[1-3].外加偏压[4-6]是电助光催化过程的一个重要特性,通过对TiO2薄膜电极施加偏压可降低光生电子和空穴的复合速率,不仅可以加速有机污染物的降解,而且还能改变某些底物的降解途径[7].     

有机碳材料在光电催化系统中的作用

有机碳材料因电荷传导效率高、结构可调、无污染等特点被广泛应用于光电催化领域。将含有机碳材料的催化剂作为电极材料已成为光电催化领域的研究热点之一。本文介绍了几种常见的有机碳材料的结构、特点、制备方法及其研究方向,并将含有机碳材料的电极进行分类。主要总结并论述了有机碳材料在光电催化系统中的五种作用:(1)作为催化剂;(2)作为光敏剂(3)作为电子介质;(4)作为催化剂载体;(5)作为光电极的稳定剂,最后阐述了有机碳材料在光电催化系统中的研究现状及难点问题。     

CdSe/泡沫镍薄膜电极对结晶紫的光电催化降解

采用恒电位电沉积法,以泡沫镍为基底电极,制备了CdSe/泡沫镍薄膜电极,采用扫描电子显微镜、紫外可见漫反射光谱和能谱分析表征了CdSe薄膜的形貌及其组成。应用该电极研究结晶紫溶液在光电催化降解过程中的COD去除率。结果表明,以白炽灯(100 W,2只)为光源,采用电沉积30 min所得的CdSe/泡沫镍薄膜电极为工作电极,外加偏压为0.4 V(vs.SCE),0.01 mol/L NaCl为电解质,光电催化降解浓度为0.001 g/L的结晶紫溶液120 min,COD去除率达到84.3%。     

负偏压下Ag@AgBr/Ni膜电极光电催化降解罗丹明B的性能和机理

用电化学方法制备Ag@Ag Br/Ni表面等离子体薄膜电极,以扫描电子显微镜(SEM)、X射线衍射(XRD)和紫外-可见漫反射光谱(UV-Vis DRS)对薄膜的表面形貌、晶相结构、光吸收特性进行了表征,在负偏压和可见光作用下,以罗丹明B为模拟污染物对薄膜的光催化活性和稳定性进行了测定,采用电化学技术和向溶液中加入活性物种捕获剂的方法对薄膜光电催化降解机理进行了探索。结果表明:最佳工艺下制备的Ag@Ag Br/Ni膜电极是由表面沉积纳米Ag的纳米晶Ag Br颗粒构成的薄膜,具有显著的表面等离子共振效应。薄膜具有优异的光电催化活性和良好的催化稳定性,在最佳负偏压和可见光照射下反应12 min,薄膜光电催化罗丹明B(c=5 mg·L~(-1))的降解率是多孔Ti O2(P25)/ITO纳米薄膜的10.2倍。相对于未加偏压的光催化,降解率提高了2.0倍;在保持薄膜光催化活性基本不变的前提下可循环使用5次。电极表面纳米Ag粒子的等离子体共振对于光阴极反应(导带反应)的活化作用是光电催化活性提高的重要原因。提出了负偏压下Ag@Ag Br/Ni表面等离子体薄膜光电催化降解罗丹明B的反应机理。     

Solar Fuels: Visible‐Light‐Driven Generation of Dihydrogen at p‐Type Silicon Electrocatalysed by Molybdenum Hydrides

We show that a robust molybdenum hydride system can sustain photoelectrocatalysis of a hydrogen evolution reaction at boron‐doped, hydrogen‐terminated, p‐type silicon. The photovoltage for the system is about 600–650 mV and the current densities, which can be sustained at the photocathode in non‐catalytic and catalytic regimes, are similar to those at a photoinert vitreous carbon electrode. The kinetics of electrocatalysed hydrogen evolution at the photocathode are also very similar to those measured at vitreous carbon—evidently visible light does not significantly perturb the catalytic mechanism. Importantly, we show that the doped (1–10 Ω cm) p‐type Si can function perfectly well in the dark as an ohmic conductor and this has allowed direct comparison of the cyclic voltammetric behaviour of the response of the system under dark and illuminated conditions at the same electrode. The p‐type Si we have employed optimally harvests light energy in the 600–700 nm region and with 37 mW cm^?2 illumination in this range; the light to electrochemical energy conversion is estimated to be 2.8 %. The current yield of hydrogen under broad tungsten halide lamp illumination at 90 mW cm^?2 is (91±5) % with a corresponding chemical yield of (98±5) %.     

层状二氧化锰和2,2'-联吡啶铁自组装膜的制备和光电性能研究

采用静电吸附层-层自组装方法制备了层状二氧化锰/2,2'-联吡啶铁自组装膜材料,借助扫描电镜(SEM),紫外可见光谱(UV-Vis)和电化学工作站等测试手段对自组装膜的结构与性能进行了表征.结果表明,该自组装膜具有均匀的表面和紧密的层状结构,在可见光照射条件下该自组装膜电极的氧化还原电流明显增加了.层状二氧化锰/2,2'-联吡啶铁自组装膜电极,在可见光照射条件下光电降解有机染料罗丹明B(1×10-5mol/L)反应80min降解率达到了57%.     

热处理气氛对 TiO2 纳米管阵列薄膜光电催化性能的影响

 采用原位阳极氧化法在 Ti 基底上制备了高度有序的 TiO₂ 纳米管阵列薄膜, 分别在 O₂, 空气, Ar 和 H₂ 气氛中于 500 oC 进行结晶热处理, 考察了热处理气氛对 TiO₂ 纳米管阵列薄膜光电催化降解亚甲基蓝 (MB) 反应性能的影响. 结果表明, 在这些气氛中热处理得到的锐钛矿晶型的纳米管阵列薄膜对 MB 降解满足一级反应, 其速率常数分别为 4.967, 3.127, 1.989 和 1.625 h^-1 (0.5 V). 电化学阻抗分析表明, TiO₂ 纳米管的光电催化性能受控于光生电荷的传递特性. 在 O₂ 中热处理, TiO₂ 纳米管的光吸收及激发性能得以改善, 且电荷传递阻抗降低, 因而其光电催化性能最好.     

TiO2膜电极光电催化降解苯甲酸的机理研究

利用自制纳米TiO2薄膜作电极, 对苯甲酸光电催化降解过程进行了系统研究. 同时利用扫描电镜(SEM)、X射线衍射图谱(XRD)和光电流-电压响应谱分析光催化剂的微观性质和光电性能. 选取较高的pH 10.5, 以利于苯甲酸降解中间产物的检测(GC/MS). 通过对比光电催化与单一的TiO2光催化体系中苯甲酸的降解动力学、总有机碳(TOC)的去除率、降解产物的生成(GC/MS)及活性自由基物种的产生(ESR), 提出光电催化降解苯甲酸的具体反应路径和氧化机理. 羟基化的苯甲酸在羟基自由基与活性氧自由基的共同作用下, 经由含六个碳原子的二酸(顺式己二烯二酸), 被进一步氧化成小分子酸和CO2.