Atomistic Observation of Temperature-Dependent Defect Evolution within Sub-stoichiometric WO_3–x Catalysts

Abstract

Tunable crystalline defects endow WO 3−x catalysts with extended functionalities for a broad range of photo-and electric-related applications. However, direct visualization of the defect structures and their evolution mechanism is lacking. Herein, aberration-corrected and in situ transmission electron microscopy was complemented by theoretical calculations to investigate the effect of temperature on the defect evolution behavior during hydrogenation treatment. Low processing temperature (100−300 °C) leads to the occurrence of randomly distributed oxygen vacancies within WO 3−x nanosheets. At higher temperatures, oxygen vacancies become highly mobile and aggregate into stacking faults. Planar defects are prone to nucleate at the surface and develop in a zigzag form at 400 °C, while treating at 500 °C promotes the growth of {200}-type stacking faults. Our work clearly establishes that the atomic configuration of the defects in WO 3−x samples could be manipulated by regulating the hydrogenation temperature. This study not only expands our understanding of the structure−function relationships of sub-stoichiometric tungsten oxides but also unlocks their full potential as advanced catalysts by tuning stoichiometry in a controlled manner.

Synergy of metallic Pt and oxygen vacancy sites in Pt–WO3−xcatalysts for efficiently promoting vanillin hydrodeoxygenation to methylcyclohexane

“…The measured value of 2.004 can be attributed to the oxygen vacancies in the lattice. 36,44 The highest intensity of EPR signal for Pt–WO 3− x indicated that it possesses the largest amount of oxygen vacancies, consistent with the XPS results. In the Raman shift results (Fig.…”

Heptazine‐Based Ordered‐Distorted Copolymers with Enhanced Visible‐Light Absorption for Photocatalytic Hydrogen Production

“…Moreover, it is clearly to observe that the photocatalytic performance for hydrogen evolution of N‐PHI x gradually increased with the calcination temperature raising from 500 to 600 °C, suggesting that the enhanced charge separation and migration efficiency by introducing more ordered‐distorted interface can improve the photocatalytic water reduction capacity. However, with calcination temperature further increased to 650 °C, N‐PHI 650 catalyst presents clearly decreased photocatalytic water reduction activity, which is probably attributed to the depolymerization of heptazine units [25] . To study the effect of the strong visible light absorption property of distorted heptazine‐based melon structure on the photocatalytic water reduction performance, the activities of N‐PHI 600 at long wavelengths have also been explored.…”

“…However, with calcination temperature further increased to 650 °C, N-PHI 650 catalyst presents clearly decreased photocatalytic water reduction activity, which is probably attributed to the depolymerization of heptazine units. [25] To study the effect of the strong visible light absorption property of distorted heptazine-based melon structure on the photocatalytic water reduction perform-…”

High-performance potassium poly(heptazine imide) films for photoelectrochemical water splitting

“…Solar-driven water splitting for hydrogen fuel production using a photoelectrochemical (PEC) platform is an appealing strategy by which to sustain energy demand. [1][2][3][4] In the PEC system, semiconducting photoelectrodes with the properties of the efficient absorption of visible light and high quantum yield have been researched for almost half a century, 5 and a variety of materials, including metal oxides, [6][7][8][9] metal oxynitrides, 10,11 perovskites, 12 polymers, 13 metal-organic frameworks [14][15][16] and other materials, [17][18][19][20][21] have been reported. Among them, conjugated polymers have received broad attention recently.…”