Oxygen-Deficient Nanofiber WO_3–x/WO₃ Homojunction Photoanodes Synthesized via a Novel Metal Self-Reducing Method

Abstract

Defect engineering of semiconductors has been identified as an efficient route toward enhancing the photoelectrochemical performances. There is a security threat in the traditional hydrogen annealing process. In this work, the oxygen-defective nanofiber WO3–x /WO3 homojunction photoanode was in situ-synthesized via a novel metal self-reducing method. The as-prepared photoanode exhibits 1.8 times higher solar water oxidation photocurrent density than that of the bare WO3 film at 1.2 V versus Ag/AgCl. The enhanced photoelectrochemical properties originate from the effective charge separation and injection, attributed to the stronger built-in electric field created by the oxygen-deficient homojunction. Importantly, this novel method is universally applicable to synthesize oxygen-deficient semiconductor materials, including films and powders.

Synthesis of N-Doped Magnetic WO3–x@Mesoporous Carbon Using a Diatom Template and Plasma Modification: Visible-Light-Driven Photocatalytic Activities

“…The major W part in the tungsten oxide composition has the 6+ oxidation state, which is confirmed by the W 4f high-resolution spectrum of WO 3 , exhibiting the peaks at 37.7 ± 0.1 and 35.6 ± 0.1 eV related to 4f 5/2 and 4f 7/2 , respectively (Figure 3c). 40 On the other hand, extra peaks at 34.3 ± 0.1 and 36.6 ± 0.1 eV in the W 4f curves of M-WO 3−x @MC and NM-WO 3−x @MC confirm the W 5+ presence as well. These results are in good agreement with the data gained from the XRD analysis, which reveals the partial reduction of tungsten oxide with the resol polymer during the EISA synthesis procedure.…”

“…These results are in good agreement with the data gained from the XRD analysis, which reveals the partial reduction of tungsten oxide with the resol polymer during the EISA synthesis procedure. 35,40 As shown in Figure 3d, the N 1s spectrum is deconvoluted into three constituents, which are related to graphitic nitrogen (402.3 ± 0.1 eV), pyrrolic nitrogen (400.2 ± 0.1 eV), and pyridinic nitrogen (398.6 ± 0.1 eV). 41 Actually, as M-WO 3−x @MC was exposed to the reactive species, their interactions resulted in the nitrogen-doped nanocomposite material with graphitic, pyrrolic, and pyridinic bonding configurations after nitrogen group transformation and the rearrangement of the structure.…”

Oxygen Vacancy Defects and a Field Effect-Mediated ZnO/WO2.92 Heterojunction for Enhanced Corrosion Resistance

“…The presence of OVs will affect the surface reaction kinetics. It could be seen from Figure 8a that WO 2.92 and ZWO 2.92 TMOs displayed a resonance signal located at a g value of 2.002, which could be attributed to OVs, 42,43 confirming the existence of unsaturated W species in mixed-valence materials. Among them, the increase in the peak intensity of the ZWO 2.92 heterojunction proved the enhancement in the concentration of OVs.…”

Highly efficient water purification by WO3-based homo/heterojunction photocatalyst under visible light

“…However, bare WOx exhibits a relatively low efficiency owing to a poor electron-scavenging pathway, which increases the recombination rate of photoexcited carriers [1]. Thus, many researchers have used bandgap engineering strategies for efficient consumption of electrons by controlling the atomic configurations of crystals [9,12], controlling the stoichiometry [13,14], elemental doping [15], compositing with noble metal nanoparticles or carbon materials as electron mediators [16,17], and combining with other semiconductors [18] to form heterojunctions.…”

“…In particular, controlling the stoichiometry and introducing oxygen vacancies is a practical approach to extend light absorption and facilitate carrier transfer/separation, which significantly improves photocatalytic performance [1]. In the last decade, various methods were used to prepare nonstoichiometric tungsten trioxides (WO3-x), such as the hydrothermal/solvothermal reaction of inorganic precursors or W [13,16], annealing WO3 in a reducing atmosphere (H2) or vacuum [7,19], and microwave plasma ablation of W in aqueous solution [20]. However, the reported approaches require unique experimental setups for thermal treatment in a vacuum or a hydrogen-rich atmosphere, high-pressure control, and introduction of specific reaction fields.…”