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Phase and Vacancy Modulation in Tungsten Oxide: Electrochemical Hydrogen Evolution
Author(s) -
Sharma Lalita,
Kumar Pawan,
Halder Aditi
Publication year - 2019
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201900666
Subject(s) - materials science , tafel equation , monoclinic crystal system , vacancy defect , phase transition , transition metal , tungsten , oxide , electrochemistry , annealing (glass) , crystallography , x ray photoelectron spectroscopy , crystal structure , chemical engineering , chemistry , condensed matter physics , metallurgy , catalysis , electrode , biochemistry , physics , engineering
Defects in crystal structures often contribute to an increase in the number of catalytically active sites and, in turn, enhance the electrochemical performances. In the present work, we modulate the phase transition of tungsten oxide from hexagonal to the monoclinic by tuning annealing conditions in vacuum environment. This phase transition also accompanies the incorporation of oxygen vacancies in crystal structures. WO 3‐ x annealed at 550 °C (Vac‐550) shows a transition from heaxagonal to monoclinic with superior hydrogen evolution activity, exhibiting a Tafel slope of only 30 mV/dec, which is comparable that of commercial Pt/C. XRD, in situ TEM, EPR, and XPS analysis provide detailed insights into the structural transition as well as oxygen vacancy concentration of the annealed WO 3‐ x samples in a vacuum environment. This work paves the way towards a generalized methodology for enhancing electrochemical activity by the vacancy modulation in transition‐metal oxides.