Vacuum Filtration‐and‐Transfer Technique Helps Electrochemical Quartz Crystal Microbalance to Reveal Accurate Charge Storage in Supercapacitors

Abstract

Electrochemical quartz crystal microbalance (EQCM) can be used to study the charge storage mechanisms of supercapacitors because of its excellent accuracy in mass change, and a homogeneous and ultrathin sample coating is strongly required for accurate measurement. However, it is difficult to obtain such a coating by the frequently used methods. Here a vacuum filtration‐and‐transfer (VFT) technique is reported to achieve this target. To prove the universality of this method, six materials with different dimensions are selected as research objects, and they are prepared into test films on quartz by VFT method and well‐used spray method for EQCM measurements, respectively. The results show that the VFT method can eliminate the influence caused by inhomogeneity of the films, which is beneficial for clearly distinguishing the rigid model from the viscoelastic model. This method helps EQCM to reflect more precise quality change as well as deformation of the material itself. Consequently, it makes EQCM more reliable to describe the energy storage mechanisms of various electrode materials.

Nanoporous carbon for electrochemical capacitive energy storage

“…Instead of typical drop coating or spray coating, a new method by using vacuum filtration has been developed to prepare homogeneous coatings on the Au coated quartz. 155 The roughness and the homogeneity of the deposit being greatly improved, more accurate measurements are obtained with a lot less frequency noise.…”

Advances in in-situ characterizations of electrode materials for better supercapacitors

“…The model in principle is only suitable to the situation in which the adsorption film is rigid and homogeneous without lateral sliding. It is believed that EDLC consists of rigid adsorption; but for pseudocapacitance, there is a controversy whether the Sauerbrey equation is proper to calculate the mass changes of an electrode in Faraday reaction [57]. To maintain the high detection sensitivity (~10 À9 g), some strict requirements on the sample preparation have to be considered in EQCM [56,57].…”

“…It is believed that EDLC consists of rigid adsorption; but for pseudocapacitance, there is a controversy whether the Sauerbrey equation is proper to calculate the mass changes of an electrode in Faraday reaction [57]. To maintain the high detection sensitivity (~10 À9 g), some strict requirements on the sample preparation have to be considered in EQCM [56,57]. Among them, a ultrathin and homogeneous sample coated on the quartz sensor is very important to enable the high fundamental resonance frequency without much damping.…”

Mass Transport Behaviors in Graphene and Polyaniline Heterostructure–Based Microsupercapacitors

“…The electrochemical quartz crystal microbalance (EQCM) research system can provide some in-depth understanding to the charge-storage mechanism through the accuracy mass transport measurement in electrochemical cycles process, especially when measuring ionic fluxes in the pore volume of AC material in an electrochemical system. [48,49] The ionic fluxes of carbon material with relatively high rigidity reveal strong sensitivity to variations in pore/ion width and partitioning ion size relative to electroactive polymers. [49,50] Experimental ion population changes (ΔΓ) as a function of charge density (ΔQ) during the charging and discharging process for PNEG.…”