金刚石薄膜电化学

金刚石由于其特殊的物理与化学性质,早在几百年前就吸引了人们对它的关注.化学气相沉积(chemical vapor deposition,CVD)法制备的高掺杂硼复合多晶金刚石薄膜,为金刚石薄膜在电化学中的应用开辟了新的领域.作为新型碳素电极材料,高掺杂硼复合多晶金刚石薄膜具有许多目前使用的电极材料所不可比拟的优异特性如:宽电化学势窗,低残留电流,极好的电化学稳定性以及表面不易被污染等.本文综述了高掺杂硼复合多晶金刚石薄膜电极在电化学中的几个重要应用,包括电分析、电合成及电化学法处理废水等.     

多晶富镉Hg_(1-x)Cd_xTe的电沉积及Hg_(0.09)Cd_(0.91)Te薄膜的光电化学行为

本文研究了在酸性CdSO_4+HTeO_2~+6HgCl_2 电解液中多晶富镉Hg_(1-x),Cd_(?),Te(x>0.5)的电沉积过程,实现了三种离子在同一电位下共沉积的技术。对在钛基底上沉积出的薄膜进行XRD,SEM和EDAX分析,结果表明薄膜为闪锌矿型的多晶结构,分布均匀连续。考察了(1—x)=0.09时多晶薄膜在多硫氧化还原电对液中的光电化学行为,光强为100mW/cm~2时,短路光电流I_(sc)=1.88mA/cm~2,开路光电压V_(oc)=0.25V,填充因子F·F=0.22。由光电化学光谱所确定出的禁带宽度E_g=1.26eV,Mott-schottky曲线给出了电极的平带电位φfb为—1.26V(vs.SCE),从而得到开路光电压V_(oc)可能达到的最大值为0.49V。因此,多晶富镉Hg_(1-x)Cd_xTe薄膜是一种很有潜力的光活性电极材料。     

涂敷氧化铁电极的光电化学和介电性质的研究

本文利用涂敷Fe(C_8H_(15)O_2)_3[2-乙基己醇酸铁(Ⅲ)]于Fe,Ti,Pt金属基片上,热氧化分解制成多晶氧化铁电极。对其介电、光电化学行为的测定,表明它们与利用热氧化法以及阳极氧化法所制成的多晶氧化铁电极的性能相似,具有n型半导体的特性。借助于交流阻抗的快速测定,并且选择了一种等效电路,测定了空间电荷区电阻、电容的变化。这种方法可以用来监测光电极的相对光效率。     

太阳能光电化学转换中的几个问题

自1972年本多等用n-TiO_2光阳极进行光助电解水以来,以半导体电极为吸光体的太阳能光电化学转换的研究工作蓬勃兴起,国内自1978年开始,也开展了这一新领域的工作。本文仅就半导体电极的研究趋向、多晶与单晶电极的特点、半导体液结的稳定性、金属薄层对半导体的保护、异结电极的能带匹配等,结合我们对半导体硅的研究加以综述。     

TiO2包覆不同微结构纳米碳纤维薄膜电极的光电化学性能

采用溶胶-凝胶法制备了TiO2包覆不同微结构的纳米碳纤维(Carbon nanofibers, CNF), 包括板式纳米碳纤维(Platelet-CNF, PCNF)和鱼骨式纳米碳纤维(Fish-bone-CNF, FCNF)的复合薄膜电极. 用光电流作用谱和光电流-电势图等方法研究了复合薄膜电极的光电化学性能. 研究结果表明, 复合薄膜电极表现出n型半导体特征, 薄膜中CNF的存在有助于光生电子和空穴有效地分离, 提高了光电转换效率, TiO2包覆PCNF薄膜电极在可见光范围内存在明显的光电响应.     

TiO_2光电化学电池催化氧化甲基红

以钛基TiO2薄膜为光阳极,研究了光电化学电池中阳极光催化降解偶氮染料甲基红的动力学.结果表明,短接光电化学电池分隔了光催化过程的阴、阳极反应,有利于抑制光生载流子的复合,提高光催化氧化速率.相同实验条件下短路光电流越大,则甲基红降解速率越高.在基底和TiO2薄膜之间夹层SnO2得到组装电极Ti/SnO2/TiO2,进一步提高了光生载流子的分离效率;同时采用电化学阻抗谱(EIS)评价了电极的光催化性能.     

TiO2／Ti／TiO2半导体隔片光电化学电池的性能

研究了半导体隔片光电化学电池(SC-SEP)中光池溶液的pH、暗池溶液的氧化还原电对以及两池中的暗电极对电池的开路电压、光生电压、短路光电流和光伏安特性的影响。对它们的影响机制进行了初步分析。通过合理选择电池体系,SC-SEP的性能可比单隔室的光电化学电池(PEC)优越。     

五甲川菁染料的敏化作用及其在Gratzel型太阳能电池中的应用

采用新染料五甲川菁(Penta Methyl Cyanine)敏化TiO2纳米结构电极,UV-Vis吸收光谱和光电化学结果表明,使用该染料敏化使TiO2纳米结构电极吸收波长红移至可见光区和近红外区,可显著地提高TiO2纳米结构电极在可见光区的阳极光电流强度,明显改善光电转换效率.结合吸收光谱、电化学和光电化学结果初步讨论了敏化电极的光生电流的机理.     

硫氰酸盐电化学氧化的动力学复杂性

本文利用多种电化学方法研究了多晶电极上硫氰酸盐电化学氧化的动力学和机理,观察到电流和电位振荡。循环伏安测量表明氧化动力学分为二步过程。除了振荡现象,系统也展示双稳态,利用时间电位扰动,氧化反应可在高电位和低电位稳态之间转换,而且强烈吸附的惰性离子也可诱导从振荡转化为稳态。     

铜电极在含苯并三唑的硼砂-硼酸缓冲溶液中的光电化学行为研究

用光电化学方法研究了铜电极在含苯并三唑(BTA)的硼砂-硼酸缓冲溶液中的光电化学行为。BTA能使铜电极的光响应由p-型转变为n-型。产生光响应的原因是铜电极表面的Cu2O膜。当BTA存在时由于BTA的作用致使电极表面Cu2O膜中共存着p-型和n-型区域, 电位正移和频率增加导致电极显示n-型光响应。     

Harmonic Analysis of Pulsed Photovoltaic Response of Titanium Dioxide Films under Local Illumination

A change in the photoelectrochemical behavior of a semiconductor–electrolyte system after transition from overall to local illumination of the electrode surface is studied. The proposed model accounts for charge interactions between illuminated and dark electrode portions and describes the frequency spectrum of photopotential for an electrode locally illuminated by a periodic sequence of light pulses a few nanoseconds in length. As shown with polycrystalline thin-film TiO₂electrodes, local values of concentrations of ionized donors and flat-band potentials of semiconductor electrodes may be determined with a harmonic analysis of frequency spectra of photovoltaic responses. The possibility of using the proposed approach in photoelectrochemical microscopy is discussed.     

FeFe]-hydrogenase-catalyzed H2 production in a photoelectrochemical biofuel cell

The Clostridium acetobutylicum [FeFe]-hydrogenase HydA has been investigated as a hydrogen production catalyst in a photoelectrochemical biofuel cell. Hydrogenase was adsorbed to pyrolytic graphite edge and carbon felt electrodes. Cyclic voltammograms of the immobilized hydrogenase films reveal cathodic proton reduction and anodic hydrogen oxidation, with a catalytic bias toward hydrogen evolution. When corrected for the electrochemically active surface area, the cathodic current densities are similar for both carbon electrodes, and approximately 40% of those obtained with a platinum electrode. The high surface area carbon felt/hydrogenase electrode was subsequently used as the cathode in a photoelectrochemical biofuel cell. Under illumination, this device is able to oxidize a biofuel substrate and reduce protons to hydrogen. Similar photocurrents and hydrogen production rates were observed in the photoelectrochemical biofuel cell using either hydrogenase or platinum cathodes.     

Protoelectrochemical properties of the single-crystal SrTiO3 doped in the surface region

The photoelectrochemical properties of the single crystal SrTiO₃, doped in the surface region are studied. It is found that the doped SrTiO₃ with Cr, Co, Pt and Rh give a relatively large photoresponse to visible light. The dark anodic currents which will be due to the resonance tunnelling or hopping mechanism are observed at the doped electrodes with the above metal cations. Therefore, it is concluded that the visible light response is mainly attributable to the formed impurity levels and/or structure defetcs by the doping metal cations near the conduction band of SrTiO₃. The above doped electrodes also bring the large cathodic photocurrent or the dark cathodic current due to the O₂ reduction, except for the Co doped electrode. This will show that the impurity levels act as the active site of O₂ reduction.     

Study on photoconductivity of dye-polymer-based solid-state thin film

In this article, we describe a solid-state photoelectrochemical cell for light detection. Safranine-T dye mixed with polyvinyl alcohol (PVA) solution was deposited on a conducting and transparent indium-tin-oxide (ITO)-coated glass that was used as one electrode and another ITO-coated glass as the counterelectrode. A solid polymeric electrolyte consisting of polyethylene oxide-ammonium perchlorate-ethylene carbonate and propylene carbonate with suitable weight ratio was prepared and sandwiched between these two ITO-coated glass electrodes, which were separated by a Teflon spacer about 50 μm thick. The cell was biased with a direct current source to make the dye and PVA-coated ITO as the anode and the other ITO as the cathode. On illumination by a tungsten lamp, from the cathode side, the change of photocurrent was measured. The dark current-voltage characteristics and the growth and decay of the photocurrent for steady and pulsed illumination were studied.     

Synthesis and electrocatalytic activity of Au/Pt bimetallic nanodendrites for ethanol oxidation in alkaline medium

Gold/Platinum (Au/Pt) bimetallic nanodendrites were successfully synthesized through seeded growth method using preformed Au nanodendrites as seeds and ascorbic acid as reductant. Cyclic voltammograms (CVs) of a series of Au/Pt nanodendrites modified electrodes in 1M KOH solution containing 1M ethanol showed that the electrocatalyst with a molar ratio (Au:Pt) of 3 exhibited the highest peak current density and the lowest onset potential. The peak current density of ethanol electro-oxidation on the Au(3)Pt(1) nanodendrites modified glassy carbon electrode (Au(3)Pt(1) electrode) is about 16, 12.5, and 4.5 times higher than those on the polycrystalline Pt electrode, polycrystalline Au electrode, and Au nanodendrites modified glassy carbon electrode (Au dendrites electrode), respectively. The oxidation peak potential of ethanol electro-oxidation on the Au(3)Pt(1) electrode is about 299 and 276 mV lower than those on the polycrystalline Au electrode and Au dendrites electrode, respectively. These results demonstrated that the Au/Pt bimetallic nanodendrites may find potential application in alkaline direct ethanol fuel cells (ADEFCs).     

The effect of various calcination treatments on the photocatalytic activity of a rod-type TiO<Subscript>2</Subscript> electrode for oxidation of ethanethiol

It was found that the photoelectrochemical performance and photocatalytic activity of rod-type TiO₂ electrodes were affected by various post-calcination treatments, for example, calcination in NH₃ or under vacuum. Post-calcination treatment in NH₃ at 773 K was particularly effective in increasing the photoelectrochemical performance and photocatalytic activity of rod-type TiO₂ electrodes. A unique photoelectrochemical circuit was constructed by connecting a rod-type TiO₂ electrode to a Pt electrode through a silicon solar cell in which the negative bias was applied on the rod-type TiO₂ electrode. It was found that the photoelectrochemical circuit can effectively oxidize ethanethiol in water into CO₂.     

Water oxidation reaction promoted by MIL-101(Fe) photoanode under visible light irradiation

This work spotlights the recently discovered photoelectrocatalytic properties of iron-based metal–organic frameworks (MOFs) for water oxidation reaction (WOR) under visible light irradiation. The low efficiency of WOR is one of the biggest difficulties faced by photoelectrochemical solar energy conversion; the development of new photoanodes for WOR is greatly desired. In view of the fact that a higher efficiency for WOR was forecast thanks to the peculiar properties of MOFs, such as a highly ordered framework and homogenous porous structure, the photoelectrodes based on MIL-101(Fe) containing photo-active iron(III) clusters have been fabricated by using a drop-casting method and applied to photoelectrochemical water oxidation as photoanodes. XRD measurements revealed the successful formation of MIL-101(Fe) electrodes while retaining their framework structures. From the results of photoelectrochemical measurements, the optimal thickness of the MIL-101(Fe) electrodes was determined to be ca. 60 μm, and the optimized MIL-101(Fe) electrode was found to promote photoelectrochemical WOR under visible light irradiation more efficiently than conventional α-Fe₂O₃ electrodes. Moreover, electrochemical impedance spectroscopy measurements demonstrated a lower resistance of charge transfer at the interface between the MOF surface and the electrolyte, resulting in better photoelectrochemical performance of the MIL-101(Fe) electrode.     

乙烯光电催化氧化的研究—金属/n-GaP光阳极

本文用光电化学的方法,研究了催化氧化乙烯兼得氢燃料的可能性,还研究了以n-GaP半导体为基底的电极表面镀金属(Au、Ag、Pd)膜,既防止光腐蚀又催化乙烯氧化反应的规律性.考察了外加偏压、pH和溶剂等因素对反应的影响,并初步探讨了可能的反应机理.     

Polycrystalline and monocrystalline antimony, iridium and palladium as electrode material for pH-sensing electrodes

Different ways of making pH-sensing electrodes from monocrystalline or polycrystalline antimony, iridium and palladium have been investigated. Monocrystalline antimony and iridium are superior to the polycrystalline elements with respect to reproducibility between electrodes and stability of the electrode potential over long periods of time. No good palladium/palladium oxide electrode could be obtained by electrochemical oxidation and the thermal preparation method could not take advantage of the properties of the monocrystalline palladium. Therefore, only polycrystalline palladium was used to study this type of electrodes. The different electrodes were compared with respect to the manner of preparation, the pH-response (reproducibility and time response) and the effect that different complexing ligands present in the measuring solutions may have on the electrode response. Also, the redox-response of the electrodes and the effect of different oxygen pressures on the electrode potentials were studied. The monocrystalline antimony electrodes have the best reproducibility and long-term stability but also respond to complexing ligands and to variations in the oxygen pressure. Monocrystalline iridium electrodes can be obtained by continuously cycling the potential between -0.25 and +1.25 V (SCE) in 0.5M sulphuric acid. They do not respond to the complexing ligands tested, and have fairly good long-term stability, but the reproducibility between electrodes is inferior to that of the monocrystalline antimony electrodes. Polycrystalline antimony and iridium electrodes were inferior to the monocrystalline ones. The properties of the palladium electrodes were similar to those of the iridium ones.