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Abstract: A photo-electrode of hydrogenated TiO2 nanorod arrays (H-TNRs) was prepared and used as a photoelectrochemical sensor for organic compound detections for the first time. Under visible light, the H-TNR electrode has shown a highly sensitive and steady photocurrent response due to introduction of oxygen vacancy and mid-gap energy levels. The H-TNRs are a promising material for photoelectrochemical detection of organic compounds under visible light. [Copyright &y& Elsevier]

Highlights: [•] Rutile nanowire arrays (RNW-TiO2) were directly grown on conductive Ti foils in a hydrothermal reactor. [•] RNW-TiO2 shows higher photoelectrocatalytic activity than rutile nanorod arrays grown on FTO substrates. [•] RNW-TiO2 is capable of oxidizing a wide spectrum of organic compounds indiscriminately. [•] RNW-TiO2 can be directly used as photoanodes to detect organic compounds. [ABSTRACT FROM AUTHOR]

Abstract: A photoelectrochemical detector (PECD) was developed for determination of organic compounds in flow injection analysis (FIA) and high performance liquid chromatography (HPLC) based on the extraordinary oxidation power of nanostructured TiO2 photoanodes under UV illumination. The PECD is a simple, small, and compact photoelectrochemical cell consisting of low cost components such as a TiO2 nanostructured photoanode and a UV-LED. Compared with conventional FIA and HPLC selective detectors, such as UV–Vis detector, electrochemical detector and fluorescent detector, the PECD has the advantage of being low cost, non-selective and sensitive. Using the FIA mode, the analytical principle of the PECD was demonstrated by detecting a large variety of organic compounds, such as sugars, amino acids, alcohol, straight chain carboxylic acids, and aromatic carboxylic acid. The PECD was subsequently coupled with a typical FIA and HPLC system for the determination of sugars. For the application in FIA, under the optimum experimental conditions, the linear ranges for glucose and sucrose were 25–600μM and 25–500μM, respectively, with the same detection limit of 10μM. When the PECD was coupled with a HPLC system, the linear range for both glucose and sucrose was 7.5–200mM with the same detection limit of 1mM under the optimal experimental conditions. [Copyright &y& Elsevier]

Abstract: An in situ photoelectrochemical method is proposed to determine adsorbed phthalic acid (PA) on the TiO2 surface in a sensitive, reproducible and accurate manner. The pre-adsorbed PA in the dark and the diffused PA from organic solution can be mineralized simultaneously under UV illumination due to the strong UV-induced oxidation power of TiO2. By controlling the UV illumination, the amount of adsorbed PA on TiO2 surface was determined in the presence of PA in a small time scale (e.g., seconds), eliminating the washing step after the adsorption reaction. This provides a convenient and effective alternative to study adsorption behaviour in low concentrations on TiO2. The proposed method was applied to determine the adsorption equilibrium constant of PA. [Copyright &y& Elsevier]

Abstract: A portable, cost-effective, environmental friendly and miniature thin-layer photoelectrochemical system in conjunction with an ultraviolet light emitting diode (UV-LED) is developed for determination of chemical oxygen demand (COD), namely UV-LED PeCOD. The COD value is directly quantified by measuring the amount of electrons captured at a nanostructured TiO2 electrode during the exhaustive photoelectrocatalytic degradation of organic species in the thin-layer cell. The key parameters of the photoelectrochemical system, such as applied potential bias, light intensity and solution pH, were investigated and optimized. Combined with a microelectrochemical system and a laptop computer, the UV-LED PeCOD system enables end-users to perform on-site COD analysis in a simple, rapid, sensitive and accurate manner. Under the optimal conditions, the system can achieve a practical detection limit of 0.2ppm COD with a linear range of 0–300ppm COD. The proposed UV-LED PeCOD technology can potentially make a revolutionary improvement to the conventional COD analysis and may be widely used in water quality monitoring industry. [Copyright &y& Elsevier]

Abstract: Titanium dioxide (TiO2) thin films fabricated with different TiO2 colloids were characterised using photoelectrochemical techniques. TiO2 colloids were firstly prepared via hydrolysis of titanium butoxide and peptisation process with no hydrothermal process (labelled as NP). The resulting colloids were then subjected to different hydrothermal processes, i.e., 15-h convection hydrothermal (labelled as CH) treatment; 5-, 10- and 15-min microwave hydrothermal treatment (labelled as M5, M10 and M15, respectively). The colloids were used to prepare TiO2 thin films on conducting indium-doped tin oxide (ITO) substrates (i.e., CH, M15, M10, M5 and NP electrodes, respectively) using a controlled dip-coating technique. The experimental results demonstrate that the oxidation capacities of the electrodes for water and glucose are in the order of CH>M15>M10>M5>NP. In contrast, the oxidation capacities of the electrodes for potassium hydrogen phthalate (KHP) are in the order of M15>M10>CH. It was also found that the CH electrode could be easily poisoned by high concentration of KHP, while microwave-processed electrodes (M15, M10 and M5) are immune from the KHP poisoning. The results presented demonstrate that microwave hydrothermal processing is a promising alternative method to the traditional convection hydrothermal treatment of colloids that provides electrodes with increased photocatalytic properties for the oxidation processes of adsorption-based organic compounds, such as KHP. [Copyright &y& Elsevier]

This work focuses on the experimental optimisation of a newly developed photoelectrochemical system for the determination of chemical oxygen demand (PECOD). This method is developed based on a photoelectrochemical degradation principle. Chemical oxygen demand (COD) is directly quantified by measuring the amount of electron transferred at a TiO2 nanoporous thin-film electrode during an exhaustive photoelectrocatalytic degradation process in a thin-layer photoelectrochemical cell. In this fashion, the COD value of a sample can be determined in a simple, rapid and accurate manner. The PECOD is a direct and absolute method that requires no calibration. The effects of important experimental conditions, such as light intensity, applied potential bias, supporting electrolyte concentration and oxygen concentration, on analytical performance have been investigated and optimum experimental conditions were obtained. Analytical linear range of 0-360 ppm COD with a practical detection limit of 0.2 ppm COD were achieved. Real sample analyses were also carried out. The results demonstrated that the measured COD values using the PECOD and the standard methods were in an excellent agreement. [Copyright &y& Elsevier]

Abstract: Inkjet printing technique is proposed for the fabrication of titanium dioxide (TiO2) photoanodes with a synthetic colloidal TiO2 ink. The resultant electrodes were characterised using materials characterisation methods (such as scanning electron microscope, X-ray diffraction and UV–vis spectrophotometer) as well as photoelectrochemical means. The preliminary results indicate that the nanostructure of the original TiO2 particles is well maintained in the printing process, and the thickness and uniformity of the TiO2 thin film can be well controlled by the simple printing technique. Combined with photoelectrochemical means, the inkjet-printed TiO2 photoanode is capable of oxidising organic compounds in aqueous solution, including weak organic adsorbates (e.g., glucose, phenol) and strong organic adsorbates (e.g., potassium hydrogen phthalate (KHP), glutaric acid, malonic acid) indiscriminately in bulk cell. This characteristic is utilized to determine chemical oxygen demand (COD) in aqueous samples. A linear range of 0–120mg/L of O2 and a detection limit of 1mg/L of O2 were achieved. The photoelectrochemical activity of the printed electrodes was found to be highly reproducible. Inkjet-printing technique can be a versatile method for mass production of TiO2 photoanodes as sensors. [Copyright &y& Elsevier]

Abstract: A simple, rapid, and effective photoelectrochemical method is proposed to quantitatively characterise photocatalytic degradation behaviour of organic compounds at nanoporous TiO2 film electrodes in a thin-layer photoelectrochemical cell. This method uses the charge obtained by integrating the photocurrent originating from the photocatalytic oxidation of organic compounds to quantify the extent of degradation. Complete mineralisation was observed for all organic compounds investigated. A double-exponential kinetic rate expression was acquired using a computer simulation method, indicating two simultaneous kinetic processes. Photocurrent profiles of different organic compounds complied well with the proposed theoretical model. Both pre-exponential and exponential constants were obtained. The rate of the fast kinetic component is 10–25 times faster than that of the slow kinetic component. It was found that the identities of organic compounds have no significant effect on the photocatalytic oxidation kinetics, whereas the availability of the organic compounds to capture photoholes plays a decisive role. [Copyright &y& Elsevier]

Abstract: Photoelectrochemical method was adopted to investigate the photocatalytic oxidation of different organic compounds. It was found that at the anatase TiO2 nanoporous electrode, the potential bias changes the rate-determining step from electron migration in the film at low potentials to photohole capture at relatively high potentials. When the applied potential bias is sufficient, the steady state photocurrent obtained reflects exclusively the rate of photohole capture at TiO2 surface. Under such conditions, the photocatalytic degradation of various organic compounds with different chemical structures was studied. At very low concentrations, the linear increase of steady state photocurrent with the concentration was observed for all compounds investigated, due to the mass transfer limitation, although the number of electron needed for complete mineralization of these compounds differs markedly. It was demonstrated that the substrate molecules that reaches the electrode surface have been exhaustively mineralized under mass transfer-controlled conditions regardless of their chemical nature. At high concentration, substrate molecules (or intermediates) are accumulated on the surface (or in the reaction zone). As a result, the steady state photocurrent deviated from the linear relationship. Under such conditions, the interaction of substrate molecules and/or partially degraded intermediates with TiO2 determines the overall photohole capture rate. The differences in photohole capture rate among different organic compounds were observed. The kinetic characteristics of different organic compounds at high concentrations were also explained based on the structural differences. [Copyright &y& Elsevier]

A unique transient photoelectrolysis technique was developed to study the photocatalytic oxidation kinetics of adsorbed organic compounds at particulate TiO2 film electrodes. The technique was employed to study the photocatalytic oxidation of a number of adsorbed dicarboxylic acids at TiO2 porous film electrodes. The adsorption of these compounds was found to be heterogeneous, with three major types of surface complexes identified—each having distinctive binding affinities to the TiO2 surface. The three thermodynamically distinctive types of surface complexes exhibit two measurable photocatalytic reaction kinetic characteristics, i.e., a fast process and a slow process. The fast kinetic process can be attributed to the photocatalytic degradation of the strongest adsorbed species at more active sites such as edge and corner titanium ions. The slow kinetic process can be attributed to the photocatalytic degradation of the medium-strength bound complexes and the weakest bound surface complexes. The rate constants for these processes were calculated by curve fitting the photocurrent transient response to a double exponential decay expression. For adsorbed oxalic acid both the fast and the slow processes were shown to be the first-order processes in which both rate constants were independent of surface coverage. For the larger dicarboxylic acids adsorbed, the rate constant for the fast photocatalytic process (kf) was found to decrease with an increase in the surface coverage. The rate constant for the slow photocatalytic process, however, was shown to be a true first-order process for all adsorbed dicarboxylic acids. The value of the rate constant (ks) was similar for all the adsorbates studied and was independent of the surface coverage. [Copyright &y& Elsevier]

A new adsorption measurement method based on photoelectrochemical oxidation principles has been developed. The method can be used to directly quantify the amount of adsorbates at a TiO2 electrode surface in a sensitive and accurate manner. The adsorption of phthalic acid was studied as a test case. The relationship between the amount of adsorbate at the TiO2 surface and the concentration of phthalic acid in the solution was obtained. The adsorption of phthalic acid on TiO2 surface was shown to follow a Langmuir type adsorption model. For the first time, the adsorption equilibrium constant of an adsorbate at TiO2 surface has been photoelectrochemically measured. The adsorption equilibrium constant of phthalate on TiO2 porous film at pH 4.0, K=4.0×104 M−1, was obtained using our method, which was close to that obtained by conventional methods. The effect of solution pH on the amount of adsorbate at TiO2 surface was also investigated. The results indicate the adsorption of phthalic acid is mainly of chemical bonding nature. [Copyright &y& Elsevier]

A simple and facile two-step method, including electrophoretic deposition and chemical bath deposition strategies, has been used to fabricate a novel interlocking g-C 3 N 4 /CdS photoanode on conductive substrate. Integrating a large area of intercontact g-C 3 N 4 /CdS heterojunction with an intimate connection between the photocatalysts and the substrate, the separation and migration of the photogenerated carriers by g-C 3 N 4 and CdS are significantly improved, and the internal resistance of the photoanode is effectively reduced. The optimal g-C 3 N 4 /CdS photoanode exhibits an excellent visible light photocurrent density of 5.4 mA cm -2  at 0.0 V bias ( vs. Ag/AgCl) and the photoelectrochemical H 2 production rate reaches 81.1 μmol h -1  cm -2 . Moreover, the stability of this interlocking g-C 3 N 4 /CdS photoanode not only reflects in a 9-hour long time recycling photoelectrochemical H 2 production test, but also in an outstanding steady structure which even be stabilized in an ultrasonic treatment. The present study provides a practical and convenient technique to develop such an earth abound and low-cost CdS/C 3 N 4 photoanode which can be used for high efficiency and stable photoelectrochemical solar energy conversion. [ABSTRACT FROM AUTHOR]

Abstract: This study compares the photocatalytic (PC) and photoelectrocatalytic (PEC) oxidation of glucose by Pt–TiO2 films under similar conditions. The overall oxidation efficiency of the PEC process was better than the PC process, for both TiO2 and Pt–TiO2 films. The Pt deposits enhanced the PEC oxidation efficiency of glucose at low cathodic (−0.1V) and low anodic potential bias (+0.1V). As the applied anodic bias was increased to >+0.5V, the undoped-TiO2 films outperformed their Pt–TiO2 counterparts. This suggests that in the studied systems, at an anodic bias of >+0.5V, more holes were available for the oxidation of glucose on the surface of TiO2 compared to Pt–TiO2 films. In the PEC systems, above a certain applied bias, Pt deposits may have a detrimental effect on the performance of a PEC system because the Pt deposits could merely block the surface of TiO2 (particularly at the highest Pt loadings). Lower measured photocurrents from Pt–TiO2 films compared to undoped-TiO2 and a decrease in the photocurrent as the Pt loading increased corroborate this postulation. [Copyright &y& Elsevier]