Unravelling the role of polyoxovanadates in electrocatalytic water oxidation reaction: Active species or precursors

• Published in: Applied surface science Vol. 540; p. 148306
• Main Authors: Hu, Na, Du, Jing, Ma, Yuan-Yuan, Cui, Wen-Jing, Yu, Bo-Rong, Han, Zhan-Gang, Li, Yang-Guang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 28.02.2021
• Subjects: Electrocatalysis; Oxygen evolution reaction; Polyoxovanadate; Structural conversion; Polyoxovanadate; Electrocatalysis; Oxygen evolution reaction; Structural conversion
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.148306

The roles and stability of polyoxovanadate-based hybrid compounds in electrocatalytic water oxidation were investigated, which verified that polyoxovanadates are not active sites but precursors for generating active species for OER reaction, suggesting an available route for the design of new nanosized vanadium-doped metal oxide catalysts. [Display omitted] •Three new POV-based hybrid compounds were synthesized as model electrocatalysts.•The real roles of POVs to be precursors in OER process have been disclosed.•The surface structural conversion process in OER was tracked and captured.•The true active components were identified to be V-doped metal oxyhydroxides. Exploring the role of polyoxometalates (POMs) in electrocatalytic oxygen evolution reaction (OER) is greatly significant for developing efficient electrocatalyst towards the sustainable energy production. Herein, three polyoxovanadate (POV)-based inorganic–organic hybrid compounds with formula of [Ni2(BBTZ)(H2O)4]V4O12·2H2O(1), [Co2(BBTZ)(H2O)4]V4O12·2H2O(2), [Ni(BBTZ)2]V2O6·2H2O(3) (BBTZ = 1,4-bis-(1,2,4-triazol-1-ylmethyl)benzene) were synthesized as electrocatalysts to explore their roles for OER. Structural analysis showed that compounds 1–2 are isomorphic 2-D wave-like layer structures, while compound 3 features 3-D framework with a 5-fold interpenetrating metal–organic moiety. Experiments showed that the three compounds can keep their structural integrities after soaking in 1 M KOH electrolyte, and compound 1 exhibited the best catalytic activity towards OER with low overpotential of 353 mV at current density of 10 mA cm−2 and small Tafel slope of 77.8 mV dec−1. However, a series of technical characterizations clearly implied that there are structural conversion processes of compounds 1–3 on electrode surface accompanying the electrocatalytic reation. The organic ligands and most of polyoxovanadate species were electrochemically extracted under anodic potential, leaving the V-doping metal oxyhydroxides as OER-active species. This work confirmed that polyoxovanadates are not active sites but precursors for generating active species of OER, and suggested an available route for designing new nanosized vanadium-doped metal oxide electrocatalysts.