Abstract
This review focuses on tungsten oxide (WO3) and its nanocomposites as photoactive nanomaterials for photoelectrochemical cell (PEC) applications since it possesses exceptional properties such as photostability, high electron mobility (~12 cm2 V−1 s−1) and a long hole-diffusion length (~150 nm). Although WO3 has demonstrated oxygen-evolution capability in PEC, further increase of its PEC efficiency is limited by high recombination rate of photogenerated electron/hole carriers and slow charge transfer at the liquid–solid interface. To further increase the PEC efficiency of the WO3 photocatalyst, designing WO3 nanocomposites via surface–interface engineering and doping would be a great strategy to enhance the PEC performance via improving charge separation. This review starts with the basic principle of water-splitting and physical chemistry properties of WO3, that extends to various strategies to produce binary/ternary nanocomposites for PEC, particulate photocatalysts, Z-schemes and tandem-cell applications. The effect of PEC crystalline structure and nanomorphologies on efficiency are included. For both binary and ternary WO3 nanocomposite systems, the PEC performance under different conditions—including synthesis approaches, various electrolytes, morphologies and applied bias—are summarized. At the end of the review, a conclusion and outlook section concluded the WO3 photocatalyst-based system with an overview of WO3 and their nanocomposites for photocatalytic applications and provided the readers with potential research directions.
Highlights
The conversion of solar-emitted electromagnetic waves to useful forms of energy is a very promising research area in the field of renewable energy production
The results show that the presence of acetate and chloride ions suppressed the release of O2
The principle of using semiconductor coatings based on tungsten trioxide for PEC cells is justified by the economic aspects associated with the low cost of the material, as well as with its physicochemical properties
Summary
The conversion of solar-emitted electromagnetic waves to useful forms of energy is a very promising research area in the field of renewable energy production. Metal-oxide nanomaterials have been thoroughly studied for the conversion of solar energy to hydrogen molecules due to their chemical and physical stability, optical and electronic properties, easy fabrication and low cost. They have shown good properties for use in photoelectrochemical devices such as TiO2 [4,5,6], α-Fe2O3 [7,8,9], BiVO4 [10,11,12], ZnO [13,14,15] and WO3 [16,17,18]. On the above properties of semiconductor materials, both suitable bandgap positions to generate hydrogen and oxygen gases and the ability to absorb a reasonable portion of the solar light spectrum are critical for water-splitting. Where Jph is the photocurrent density, h is Planck’s constant, c is the light speed, Pmono is the power of calibration and monochromatic illumination, and λ is the wavelength of monochromatic light
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