Ion intercalation dynamics of electrosynthesized mesoporous WO₃ thin films studied by multi-scale coupled electrogravimetric methods

Abstract

Mesoporous WO3 thin films were prepared electrochemically by using an ionic surfactant during the synthesis, and the electrochemical properties are investigated in comparison with their dense analogues. This report specifically highlights the suitability of a time resolved coupled electrogravimetric method to follow meticulously the ion intercalation/extraction phenomena which revealed the enhanced ion intercalation/extraction behavior of electrodeposited mesoporous WO3 thin films for diverse applications in energy storage and electrochromism. This methodology (electrochemical impedance spectroscopy (EIS) and its coupling with a fast quartz crystal microbalance (QCM)) has the ability to detect the contribution of the charged or uncharged species during the electrochemical processes, and to deconvolute the global EQCM responses into the anionic, cationic, and the free solvent contributions. Our study identifies the involvement of several charged species (Li(+), Li(+)·H2O) in the compensation of charge, and H2O molecules indirectly contribute to the process in both dense and mesoporous WO3 thin films. Even a slight contribution of ClO4(-) ions was detected in the case of mesoporous analogues. The results of the study indicate that the transfer resistances of Li(+) and Li(+)·H2O are decreased when the WO3 films are mesoporous. A more significant difference is observed for the larger and partially dehydrated Li(+)·H2O ions, suggesting that increased surface area and pore volume created by mesoporous morphology facilitate the transfer of larger charged species. The relative concentration changes of cations are also magnified in the mesoporous films. The final concentration variations are higher in mesoporous films than that in the dense analogues; ∼4 times and ∼10 times higher for Li(+) and for Li(+)·H2O, respectively. To the best of our knowledge, an unambiguous identification of species other than desolvated cations (e.g. Li(+) ions), the information on their transfer dynamics and quantification of the transferred species have never been reported in the literature to describe the charge compensation process in WO3 based electrodes.

Advanced Nanoporous Material–Based QCM Devices: A New Horizon of Interfacial Mass Sensing Technology

“…A mesoporous WO 3 thin film, that was fabricated by an ionic surfactant (sodium dodecyl sulfate, SDS) assisted electro-deposition method, showed a rapid QCM sensing ability to detect the contribution of the charged or uncharged species during the electrochemical processes. [103] In situ synthesis approach for the reduction of Au nanoparticles onto a magnetic mesoporous CoFe 2 O 4 nanostructure (Au-MMNs) and the Au-MMNs based QCM sensor showed a good conjugation capability toward biomolecules. [104] A Pearson's hard and soft acid and base (HSABs) theory was employed for the successful synthesis of urchin-like hollow sphere Zn 2 SnO 4 /SnO 2 by a two-step hydrothermal synthesis process.…”

Gravimetric and dynamic deconvolution of global EQCM response of carbon nanotube based electrodes by Ac-electrogravimetry

“…, to be simultaneously obtained at a given potential [12][13][14][15]. The measurements were performed in 0.5 M NaCl at pH=7 and at every 100 mV in the following potential range: -0.45 V-0.45 V vs Ag/AgCl.…”

“…where ω=2πf is the pulsation, Rt FG  , of the species at the film/electrolyte interface [12][13][14][15].…”

“…Here, an alternative characterization tool was proposed which couples fast quartz crystal microbalance (QCM) and electrochemical impedance spectroscopy (EIS) (also called acelectrogravimetry) [12][13][14][15]. It was employed to characterize supercapacitive charge storage mechanism of single wall carbon nanotube (SWCNT) based electrodes revealing the unique sensitivity of the ac-electrogravimetry to provide gravimetric and dynamic deconvolution of a global EQCM response.…”

Elucidating the Origin of the Electrochemical Capacity in a Proton-Based Battery HxIrO4 via Advanced Electrogravimetry

“…Essential to this technique, alike typical EIS measurements, the data needs to be fitted with a suitable model to extract parameters related to the interfacial transfer. The fitting methodology has been described in several works [27][28][29][30][31] and is recalled at the Supporting Information Part IV. This method was then employed for the Electrode-Electrolyte Interface (EEI) analysis of H x IrO 4 composite electrode as shown schematically in Figure SI-6.…”