Lindqvist Polyoxoniobate Ion-Assisted Electrodeposition of Cobalt and Nickel Water Oxidation Catalysts

Abstract

A method has been developed for the efficient electrodeposition of cobalt and nickel nanostructures with the assistance of the Lindqvist ion [Nb6O19](8-). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry, and a range of electrochemical techniques have been used to characterize the morphology, composition, catalytic water oxidation activity and stability of the films in alkaline solution. SEM images show that films consisting of nanoparticles with diameters of ca. 30 to 40 nm are formed after 40-50 potential cycles of deposition. Nb and Co/Ni are detected in the films by EDX. ICP-MS results show an elemental ratio of 1:1 for Co:Nb and 1:3 for Ni:Nb, respectively. Raman spectra reveal the presence of both [Nb6O19](8-) and Co(OH)2/Ni(OH)2. The films exhibit excellent stability and efficiency for electrocatalytic water oxidation in alkaline solution. Turnover frequencies of 12.9 and 13.2 s(-1) were determined by rotating ring disk electrode voltammetry at an overpotential of 480 mV for Co and Ni films, respectively. Fourier transformed large amplitude alternating current (FTAC) voltammetry reveals an additional underlying oxidation process for Co under catalytic turnover conditions, which indicates that a Co(IV) species is involved in the efficient catalytic water oxidation reactions. FTAC voltammetric data also suggest that the Ni films undergoes a clear phase transformation upon aging in aqueous 1 M NaOH and the electrogenerated higher oxidation state Ni from β-NiOOH is the more active form of the catalyst.

A Polyoxoniobate/g-C3N4 Nanoporous Material with High Adsorption Capacity of Methylene Blue from Aqueous Solution

“…After cooling to room temperature, the resulting yellow sample was obtained. NbO was prepared according to the previous literature and its identity was further confirmed by IR spectrum (Liu et al, 2015 ). Two hundred milligrams of NbO was dissolved in 15 mL distilled water, and then 184 mg of as-prepared g-C 3 N 4 were added into the aqueous solution.…”

Characterization of decavanadate and decaniobate solutions by Raman spectroscopy

“…40 This dissociation is suspected to be reversible, based in part on isotope-transfer between the Nb 10 and Nb 6 although the thermodynamics of the equilibrium remains unexplored. 40 36 it is unlikely that there is any polyoxoniobate chemistry beyond the Nb 6 ion in the alkaline direction.…”

Polyoxometalates: Tailoring metal oxides in molecular dimension toward energy applications

“…Polyoxoniobate hybridizes with CdS to photocatalyze the hydrogen formation and degrade dye pollutes . The Lindqvist‐type polyoxoniobate H 2 TeNb 5 O 19 with tellurium substitution and similar polyoxoniobates such as Nb 24 O 72 ‐based polyoxoniobate with copper inclusion exhibit potentials for hydrogen evolution reactions . Nb 10 ‐ and Nb 12 ‐based polyoxoniobates have been synthesized with their Keggin‐type structures determined and exhibit potentials as hydrogen evolution materials .…”

“…323 The Lindqvist-type polyoxoniobate H 2 TeNb 5 O 19 with tellurium substitution and similar polyoxoniobates such as Nb 24 O 72 -based polyoxoniobate with copper inclusion exhibit potentials for hydrogen evolution reactions. [324][325][326] Nb 10 -and Nb 12 -based polyoxoniobates have been synthesized with their Keggin-type structures determined and exhibit potentials as hydrogen evolution materials. 327 Polyoxoniobate-based composites such as those coupled with polyoxovanadate are used as efficient catalysts.…”