Enhanced Electrocatalytic Oxygen Reduction on NiWO_x Solid Solution with Induced Oxygen Defects

Abstract

The continuous solid solution NiWO is successfully prepared by using precursor WO with plenty of oxygen defects. The NiWO nanoparticles are characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray absorption spectroscopy. The crystallographic phase of NiWO is stable and characterized by the same feature of the parent lattice WO even with various concentrations of dopant Ni which indicates the existence of oxygen defects. The NiWO nanoparticles could be processed as the appropriate promoter after loading 10 wt % Pt. The Pt/NiWO displays remarkable response for oxygen reduction reaction in alkaline medium compared with the commercial Pt/C. The analysis of the electrochemistry data shows that the existence of abundant oxygen defects in the solid solution NiWO is the key factor for the improved ORR catalyst performance. Ni is effective in the catalysts because of its compatibility with W in the solid solution and its active participation in oxygen reduction reaction.

Partial Dehydration in Hydrated Tungsten Oxide Nanoplates Leads to Excellent and Robust Bifunctional Oxygen Reduction and Hydrogen Evolution Reactions in Acidic Media

“…The electron-transfer numbers ( n ) were calculated (considering n = 4 for Pt/C) to be 4.13, 3.936, and 3.988 for the WO 3 ·H 2 O, WO 3 ·0.33H 2 O, and WO 3 ·2H 2 O phases, respectively. The results indicate that WO 3 ·2H 2 O and WO 3 ·0.33H 2 O follow a four-electron pathway for the complete reduction of O 2 to H 2 O. , The value obtained for n is similar to those of previous reports on W-based catalysts, such as n = 3.94 for Pt/NiWO x and n = 3.8 for an RGO/ZnWO 4 /Fe 3 O 4 nanocomposite . It is noted that the n value exceeding 4 (for the case of WO 3 ·H 2 O) could be related with the limitation of the K–L calculation method.…”

“…At higher rotation rates, more O can diffuse to the electrode surface, resulting in larger reducing currents. The K−L plots obtained for different catalysts (Figure 4C) show a linear relationship between J k −1 and ω −1/2 , 50,51 The value obtained for n is similar to those of previous reports on W-based catalysts, such as n = 3.94 for Pt/NiWO x and n = 3.8 for an RGO/ZnWO 4 /Fe 3 O 4 nanocomposite. 52 It is noted that the n value exceeding 4 (for the case of WO 3 •H 2 O) could be related with the limitation of the K−L calculation method.…”

Low- and High-Index Faceted Pd Nanocrystals Embedded in Various Oxygen-Deficient WOx Nanostructures for Electrocatalytic Oxidation of Alcohol (EOA) and Carbon Monoxide (CO)

“…This is suggestive of the nonstoichiometric features of the as-synthesized materials. Moreover, the composites of Pd–WO x , which has varied valence oxides on the surface, may be considered as another type of perovskite (ABO x ) in which A is Pd and B is W. In addition, in the Pd–W–O system, both PdO and WO x are potential catalysts for the electrocatalytic oxidation of alcohol and CO . The O 1s spectrum is shown in Figure h–j, and the peak observed at 524.9 eV is related to the Pd–O bonds.…”

“…Several important conclusions can be drawn from the analysis of XPS images, so the calculated surface atomic O/W ratios of synthesized materials. Moreover, the composites of Pd−WO x , which has varied valence oxides on the surface, may be considered as another type of perovskite (ABO x ) in which A is Pd and B is W. In addition, in the Pd−W−O system, both PdO and WO x are potential catalysts for the electrocatalytic oxidation of alcohol and CO. 47 The O 1s spectrum is shown in Figure 5h−j, and the peak observed at 524.9 eV is related to the Pd−O bonds. The other three oxygen signals located at the binding energies of 527.9, 530.2, and 532.9 eV are related to the lattice O 2− (W−O bonds), hydroxyl (W−OH, tungsten bronze) species, and adsorbed water molecule (H 2 O), respectively.…”

Enhanced visible-NIR absorption and oxygen vacancy generation of Pt/HxMoWOy by H-spillover to facilitate photothermal catalytic CO2 hydrogenation

“…29 In addition, aliovalent ion doping creates a larger number of defects (such as oxygen vacancies) in the lattice and thereby changes the valence state of an element in an oxide, providing an opportunity to promote the adsorption of target reactants and the utilization of photoinduced electrons. 30,31 Wang et al reported that doping Mo atoms into WO x can promote photoinduced electron-hole pair separation and facilitate the transfer of photoinduced electrons from active sites to CO 2 , thereby increasing the efficiency of the photoreduction of CO 2 to CH 4 . 32 Xiong et al demonstrated that doping Mo 5+ into WO x nanowires can create massive defects (oxygen vacancies), resulting in the centers of Mo-W moieties being the active sites for the chemisorption of N 2 molecules.…”