Photocatalytic fuel cells (PFC) are primarily a synergistic integration of two emerging technologies, namely, photocatalysts (PC) and fuel cells (FC). Together, the solar PC can decompose organic compounds, while FC provides an electrical potential bias to drive transport of the photogenerated electrons. Thus, electron-hole recombination in the PC mechanism can be minimized. PFC can be effectively applied to utilize solar energy for wastewater treatment and recovery of the energy chemically stored in wastewater since different Fermi levels between the photoanode and photocathode form an internal bias. Therefore, it is a promising technology for solving both environmental and energy problems. Recent research efforts have improved PFC technologies with better visible-light photoelectrodes, innovative cell designs, and optimal control. The present knowledge and understanding of PFC will help identify proper research directions for rapid enhancement of PFC technologies. To help further improve the performance of PFCs, this thesis reports on the following three main experimental parts:

Bismuth vanadate (BiVO4) has recently emerged as a promising photocatalyst for both solar energy conversion and photocatalytic degradation of organic compounds. A new fabrication method was developed to produce a highly photoresponsive BiVO4 film by growing flower-like monoclinic scheelite BiVO4 on FTO glass directly. The whole processes included a solvothermal step and a hydrothermal step synergistically helped form BiVO4 films. Optimized fabrication conditions with respect to the solvent of the precursor solution and the temperature of the solvothermal process were identified by parametric analysis. The hardness of the BiVO4 film produced by this new method was significantly improved compared to those prepared by conventional physical methods. Meanwhile, the obtained monoclinic scheelite BiVO4 film exhibited superior photocatalytic activity under simulated solar irradiation. When using the present BiVO4 film for electricity generation in a photoelectrochemical system, the photocurrent density was as high as 0.81 mA cm-2 at 1.23 V vs. RHE.

A dual photoelectrode PFC system based on a BiVO4/TiO2 nanoflake photoanode and Cu2O/Cu photocathode was designed. The optimized photoanode synthesis conditions were obtained through control of the type of solvent and precursor solution concentration. The TiO2 block layer clearly effectively enhanced the charges diffusion and transport, which decreased the electron loss. The resulting BiVO4/TiO2 photoanode had a photocurrent density of about 2.4 mA cm-2 at 1.23 V vs. RHE in a 0.5 M phosphate buffer solution (PBS) with 1 M sodium sulfite (Na2SO3) as the electrolyte under illumination with AM 1.5G solar light. Compared with the previously reported bare TiO2 and bare BiVO4-based PFC systems, the thin TiO2 block layer not only improved the charge carrier separation capacity but also enhanced the light harvesting. The degradation efficiency was measured using methylene blue as a model organic substrate with zero external bias, and the degradation reached 91.5% after 6 h.

Finally, a novel Ni-Fe layered double hydroxide (NiFe-LDH)-enhanced BiVO4 photoanode was synthesized using a hydrothermal method and was used for enhanced degradation of organic compounds and simultaneous electricity generation using a PFC system. Using methylene blue (MB) as the organic substrate and Na2SO4 as the electrolyte, the resulting NiFe-LDH/BiVO4 photoanode had a photocurrent density of about 0.62 mA cm-2 at 1.0 V vs. SCE in 0.5 M Na2SO4 under illumination with AM 1.5G solar light. Then, the NiFe-LDH/BiVO4-Cu2O/Cu PFC system had the highest short circuit current of 0.251 mA cm-2, an open-circuit voltage of 0.742 V, and a maximum power density of 0.186 mW cm-2. The proposed heterojunction photoanode not only decreased the interface recombination at the NiFe-LDH/BiVO4 junction but also enhanced the charge transport. In this case, the NiFe-LDH layer greatly enhanced the propensity for surface-reaching holes to reduce interface recombination and created a more favourable Helmholtz layer potential drop.