Enhanced Visible Light Activity of Single-Crystalline WO₃ Microplates for Photoelectrochemical Water Oxidation

Abstract

The preparation of metal oxides on a conductive substrate has been an important issue for improving photoelectrochemical water splitting efficiency. In this work, a facile synthetic process is reported for single-crystalline WO3 microplates with variable thicknesses grown directly on a fluorine-doped tin oxide substrate followed by an annealing procedure. The WO3 microplate electrode showed an improved photocurrent under 1 sun irradiation (1.9 mA/cm2 at 0.6 V vs Ag/AgCl, 100 mW/cm2) for water oxidation, including a significant enhancement in the visible light region compared to either a nanoparticle or a bulk film electrode. The enhanced water oxidation activity originates from both the single crystallinity with an optimum thickness and the oxygen-deficient characteristic of the WO3 microplates. To improve the photochemical stability, FeOOH electrocatalysts were deposited on the surfaces of the WO3 microplates. The resulting WO3/FeOOH composite electrode showed enhanced stability for water oxidation reactions.

Sonochemical synthesis of ZnO‐ZnS core‐shell nanorods for enhanced photoelectrochemical water oxidation

“…Effective photocurrent generation in the ZnO nanorods electrode can be mainly attributed to the single‐crystalline nature of the ZnO nanorods. The single‐crystalline structure has fewer grain boundaries compared with bulk film, and so can offer direct conduction paths for photogenerated electrons, and thus yield superior PEC performances . However, nanostructures are also associated with significant disadvantages, such as an increased number of surface recombination sites and a reduced space‐charge region, with the result that the ZnO electrodes had much lower efficiency than their theoretical value.…”

“…The single-crystalline structure has fewer grain boundaries compared with bulk film, and so can offer direct conduction paths for photogenerated electrons, and thus yield superior PEC performances. 31 However, nanostructures are also associated with significant disadvantages, such as an increased number of surface recombination sites and a reduced space-charge region, 32 with the result that the ZnO electrodes had much lower efficiency than their theoretical value. The photocurrent from the ZnO nanorods for water oxidation was far lower than that of sulfite oxidation (Figure 7).…”

Enhanced photocatalytic performance of tungsten oxide through tuning exposed facets and introducing oxygen vacancies

“…[1] Tungsten oxide is made up of perovskite units and is one of the most-attractive candidates for photocatalysis, as it exhibits approximately absorption of 12% of the solar spectrum (Eg= 2.5-2.8 eV), a moderate hole-diffusion length (150-500 nm) compared with α-Fe 2 O 3 (2-4 nm), and better electron transport (~12 cm 2 V -1 s -1 ) compared with TiO 2 (~0.3 cm 2 V -1 s -1 ). [1,2] However, bulk tungsten oxide often has some drawbacks such as insufficient quantum efficiency and high recombination rate of the photoproduced electron-hole pairs, which limit its practical application on photocatalytic field.…”

Hexagonal tungsten oxide nanoflowers as enzymatic mimetics and electrocatalysts

“…S10 ), regardless of Nf coating or the addition of H 2 O 2 , no redox responses were observed in the potential range. However, after modification by WONFs, a reduction peak was observed at −0.25 V, and upon the addition of H 2 O 2 to WONFs/Nf/GCE, its reduction current decreased with increasing H 2 O 2 concentration because of its electrocatalytic effect 52 53 . Figure S11 shows the CV spectra of WONFs/Nf/GCE with H 2 O 2 at different pH values (3.0–6.0); these results represent a similar trend to the results of the colorimetric detection experiment.…”