氧化铁电极的半导体性能和光电化学 Ⅴ.烧结掺锌氧化铁电极的光电响应

Somorjai等曾报道在不同电势下,测得掺MgO氧化铁光电极具有n,p两种类型的光响应^[1]。最近本实验室首次报道了在同一电势下,热形成的掺MgO-Fe₂O₃光电极具有n,p型双重光响应共存现象^[2],由于其在电催化等中可能的应用价值引起了较广泛的兴趣。     

All-solid-state potassium-selective electrode using graphene as the solid contact

Graphene sheets are used for the first time to fabricate a new type of solid-contact ion-selective electrode (SC-ISE) as the intermediate layer between an ionophore-doped solvent polymeric membrane and a glassy carbon electrode. The new transducing layer was characterized by transmission electron microscopy, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The performance of the new K(+-)selective electrodes was examined by a potentiometric water layer test, potentiometric measurements, and current reversal chronopotentiometry. The obtained potentiometric sensors were characterized with a calibration line of slope close to Nernstian (59.2 mV/decade) within the activity from 10(-4.5) to 0.1 M. The high capacitance of the graphene solid contacts results in a signal that is stable over one week. The short response time is less than 10 s for activities higher than 10(-5) M. The potential drift of the electrodes was calculated from the slope of the curves at longer times (ΔE/Δt = 1.2 × 10(-5) V s(-1) (I = 1 nA) and ΔE/Δt = 5.5 × 10(-5) V s(-1) (I = 5 nA)). All the results indicate that graphene is a promising material for use as a transducer layer for SC-ISEs.     

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。     

具有金属薄层的p-Si阴极在碱溶液中的光电化学性能

本文用循环伏安曲线和恒电位极化方法考察了具有金属薄层的p型单晶外延硅(p⁺/p-Si)阴极在碱溶液中的光电化学性能。结果表明,镀有钨-镍合金层的p⁺/p-Si阴极和镀有钯的p⁺/p-Si阴极,使氢析出的光电流明显增加。前者的电位比光电流达到相同值的空白p⁺/p-Si电极向正方移动了0.3V以上,后者移动0.25V。同时对p型外延硅(p⁺/p-Si)阴极比p型单晶硅(p-Si)阴极光响应较大的实验结果作了初步解释。扫描电镜结果显示,钨-镍合金沉积层是由许多不连续的“团块”构成的,而不是连续层。     

Electrochemical behavior of pyrroloquinoline quinone immobilized on silica gel modified with zirconium oxide

Pyrroloquinoline quinone (PQQ) was immobilized on the silica gel surface modified with zirconium oxide, designated as Si:Zr, by the carboxylic groups of the PQQ molecule and the zirconium oxide on the silica surface. The electrochemistry of PQQ immobilized on the Si:Zr matrix, incorporated in a carbon paste electrode, was evaluated using the cyclic voltammetry technique. The Si:Zr:PQQ-modified electrode showed a redox couple at E(m)=(E(pa1)+E(pc))/2=-0.150 V vs SCE at pH 7, close to that observed in aqueous solution, and another oxidation peak, E(pa2)=-0.100 V vs SCE. Studies in different pH solutions in the range of 3-7 showed that the first oxidation peak, E(pa1), is highly dependent on the solution pH shifting from to -0.175 to 0.100 V vs SCE, while E(pa2) remains practically constant at 0.100 V as the pH decreases from 7 to 3. The immobilized PQQ electrode presented the property to electrocatalyze the NADH at 150 mV vs SCE. The effect of addition of Ca(2+) ions on the electrode electroactivity for the NADH oxidation was also verified. Different from that observed for the PQQ immobilized on other electrode materials, the Ca(2+) ions did not influence the electrocatalytical response; however, the electrode stability was considerably improved in the presence of Ca(2+) ions, indicating that the matrix surface has a great influence on the electrochemical behavior of PQQ.     

Studies on the Electrochemistry of Dopamine at a Pyrocatechol Sulfonephthalein Modified Glassy Carbon electrode

IntroductionThere has been a considerable interest in developing the methods to measure the secretionneurotransmitters. Electrochemical teChniques have proven to be significantly advantageous tothe biosciencesLlj. The application of ultramicroelectrodes to neuroscien.ce, which has been pioneered by Adams[2], to monitor the concentration of neurotransmitters in the central nervesystem has had a special impact. Several neurotransmitters, e. g., dopamine(DA) are electroactlve and therefore can …     

不锈钢的光电响应测定

未经热或阳极氧化处理的不锈钢的光电响应极其微弱,测量很困难。至今,文献中尚未见有明确涵义的有关未经处理的不锈钢/溶液体系光电响应报道,仅等在这方面有过定性的研究,提及其为n型导电。本文采用了信号平均技术检测微弱的光响应,将多次信号叠加以提高其检测灵敏度。考虑到简化数据分析,用不含紫外光线的光源。在可见光谱段首次定量地测出了未经处理的1Cr18Ni9Ti不锈钢在溶液中的开路电极电势光响应(E_(ph,oc))波形、光电压波形峰-峰值(△V_(ph))～电极电势(E)的曲线,见图1和图2。     

An electrochemical and DFT study on selected beta-diketiminato metal complexes

Selected homoleptic metal beta-diketiminates M(I)L and M(II)L2 [M(I) = Li or K, M(II) = Mg, Ca or Yb; L: L(Ph) = [N(SiMe3)C(Ph)]2CH, L(Bu(t)) = N(SiMe3)C(Ph)C(H)C(Bu(t))N(SiMe3), L* = [N(C6H3Pr(i)2-2,6)C(Me)]2CH] have been studied by cyclic voltammetry (CV). The primary reduction (E(p)red, the peak reduction potential measured vs. SCE in thf containing 0.2 M [NBu4][PF6] with a scan rate 100 mV s(-1) at a vitreous carbon electrode at ambient temperature) is essentially ligand-centred: E(p)red being ca. -2.2 V (LiL(Ph) and KL(Ph)) and -2.4 V [Mg(L(Ph))2, LiL(Bu(t)) and Ca(L(Ph))2], while LiL* is significantly more resistant to reduction (E(p)red = -3.1 V). These observations are consistent with the view that the two (L(Ph)) or single (L(Bu(t))) C-phenyl substituent(s), respectively, are available for -electron-delocalisation of the reduced species, whereas the N-aryl substituents of L* are unable to participate in such conjugation for steric reasons. The primary reduction process was reversible on the CV-time scale only for LiL(Bu(t)), Ca(L(Ph))2 and Yb(L(Ph))2. For the latter this occurs at a potential ca. 500 mV positive of Ca(L(Ph))2, consistent with the notion that the LUMO of Yb(L(Ph))2 has substantial metal character. The successive reversible steps, each separated by ca. 500 mV, indicate that there is strong electronic communication between the two ligands of Yb(L(Ph))2. The overall three-electron transfer sequence shows that the final reduction level corresponds to [Yb(II)(L(Ph))2-(L(Ph))3-]. DFT calculations on complexes Li(L(Ph))(OMe2)2 and Li2(L(Ph))(OMe2)3 showed that both HOMO and LUMO orbitals are only based on the ligand with a HOMO-LUMO gap of 4.21 eV. Similar calculations on a doubly reduced complex Yb[(mu-L(Ph))Li(OMe2)]2 demonstrated that there is a considerable Yb atomic orbital contribution to the HOMO and LUMO of the complex.     

锌银电池中氧化银电极的光电化学研究

用光电化学方法研究棒状和多孔氧化银电极在阳极极化过程中的光响应规律可以得到许多信息。最大光响应出现在电极表面的AgO被充分地还原为Ag_2O以及Ag结晶即将生成瞬间, 多孔电极和实体电极开路光电位ΔV_(ph,oc)之比有助于对多孔电极孔结构的了解, 首次观测到n-p-n光响应波形的转化。     

Promoted photoelectrochemical activity of BiVO<Subscript>4</Subscript> coupled with LaFeO<Subscript>3</Subscript> and LaCoO<Subscript>3</Subscript>

BiVO₄ has emerged as a promising material for solar water splitting. The poor ability of charge transport and separation always limits its performance for photoelectrochemical water splitting. Herein, we coupled n-type BiVO₄ with p-type LaFeO₃ and LaCoO₃, achieving a photocurrent more than two times as high as bare BiVO₄ at 1.23 V versus a reversible hydrogen electrode. Also, the onset potential was negatively shifted about 260 mV. The promotion of performance is mainly because the space charge layer in BiVO₄ is broadened, and the band bend is enhanced, which facilitates the separation and transport of photo-generated charges.