Solar-driven water-splitting is a feasible route for hydrogen generation, since the process emulates the conversion in plants through natural photosynthesis (NPS). Light energy is converted into chemical energy, like oxygen and carbohydrate. Since the first study on photochemical photolysis of water by Fujishima and Honda in 1972, the photo-electrochemical (PEC) splitting of water technology has drawn much attention for its potential applications in renewable energy utilization and energy structure transition.In the PEC water-splitting process, hydrogen is produced from water using inexhaustible sunlight and specialized semiconductors, making it a more environmentally friendly and feasible way without carbon dioxide or dust production from reactions. However, it remains a technological challenge to construct a novel catalyst to drive the reaction, at a scale and cost comparable to fossil fuels. Significant advances in light utilization and high solar to hydrogen conversion efficiency are still required. Compared with the photocatalytic process, water splitting in a PEC cell employs a semiconductor electrode to separate hydrogen and oxygen production spatially: the photoanode for oxidation, and the cathode for reduction. During this process, an external bias potential is required to improve hydrogen generation highly. Designing a novel nanostructured photoelectrode with an excellent visible light response and stability will bring new advances to this field. Of all the catalysts, TiO2, WO3, BiVO4, Fe2O3, and ZnO have been extensively studied in the PEC process. Among the photocatalysts, TiO2 is a promising visible-light-driven photocatalytic material with a band gap of 3.2 eV of anatase phase, and 3.0 eV of rutile phase. As an oxide, TiO2 can be used to split water directly. Varieties of strategies (such as nanostructure, doping, surface modification) have been conducted for enhancing the energy conversion efficiency of TiO2 photoelectrodes.A series of TiO2 rutile and anatase nano-branched electrodes were prepared by combining electrospinning and hydrothermal processes in this work. The experimental results showed this branched multiphase TiO2 film was a combination of anatase nanofiber and rutile nanorods. Within the interface of multiphase TiO2, the homojunction promoted the charge separation, improved the charge transfer rate, and then acquired a relatively high efficiency for photo-electrochemical water splitting. The photo-electrochemical test results showed that 3 hours' hydrothermal deposition yielded the highest photo-electrochemical performance for the branched multiphase TiO2 film. The photocurrent density reached 0.95 mA/cm2 at the 1.0 V vs. Ag/AgCl. Moreover, this work described here provides a generic route for fabricating other multiple metal oxide photoelectrodes for photo-electrochemical applications.

Enhanced Solar-Driven Photoelectrochemical (Pec) Splitting by Heterojunctions at Multiphase Tio2 Interfaces

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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