The effect of potential bias, light intensity, and the concentration of the photohole scavenger (glucose) on the photocurrent responses of the nanoporous TiO 2 film electrodes were investigated with the focus on the overall photoelectrocatalytic oxidation process. The electron transport in TiO 2 film was the rate-limiting step at low potential bias, while the interfacial reactions became rate-limiting step at high potential bias. A linear photocurrent/potential characteristic can be obtained within a wide range of applied potential bias. Within this linear range, the electrodes behave as a constant resistance rather than a variable resistance, which is unlike a photoelectrochemical process at a bulk semiconductor electrode. The resistance consists of two components: a variant component and an invariant component. The former is inversely proportional to maximum photocurrent, due to the free electron concentration change as a result of the consumption of photoholes through interfacial reaction. The hypothesis of the photoelectron and photohole separation being fulfilled through interfacial reaction was confirmed experimentally. The invariant component of the resistance is attributed to the sum of ohmic contact impedance at the ITO/TiO 2 interface and crystalline boundary impedance during electron migration under an electric field. A model for the overall photoelectrocatalytic oxidation process was proposed and explained based on the experimental results.

A novel rapid methodology for the determination of chemical oxygen demand (COD) based on photoelectrochemical oxidative degradation principle (PECOD) was proposed and experimentally validated. With this new method, the extent of degradation of dissolved organic matter in a water sample is measured simply by directly quantifying the extent of electron transfer at a TiO 2 nanoporous film electrode during an exhaustive photoelectrocatalytic degradation of organic matter in a thin layer photoelectrochemical cell. The PECOD method demonstrated in this work is a direct and absolute method. It does not require the use of standard for calibration. The method, in principle, measures the theoretical COD value due to the extraordinary high oxidation efficiency and accuracy of charge measurement. This new approach overcomes many of the current problems associated with existing oxygen demand techniques (e.g., the matrix effect, one of the serious practical problems that most rapid COD methods suffered because of the insufficient oxidation efficiency). The PECOD method overcomes the matrix effect by employing a highly effective photoelectrochemical system that is capable of fully oxidizing a wide spectrum of organics in the water sample. The method was successfully applied to determine the COD of a range of synthetic and real samples. Excellent agreement with a standard dichromate method was achieved. The practical detection limit of 0.2 mg L -1 COD with the linear range of 0-200 mg L -1 was also achieved. The PECOD method is a method that is environmentally friendly, robust, rapid, and easily automated. It requires only 1-5 min to complete an assay and consumes very limited reagent (electrolyte only).

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The synthesis and utilization of electrodes modified with conducting polymers is reviewed. Specific issues evaluated include the various approaches available to produce the required functionality at the electrode surface and the practical considerations to be addressed during synthesis, both in terms of hardware requirements and the chemistry of electropolymerization. The review concludes with a survey of the many applications of polymer‐modified electrodes and includes 112 references.