Tag Archive for: EQCMD

Publication on AWSensors technology

Understanding Electrolyte Ion Size Effects on the Performance of Conducting Metal–Organic Framework Supercapacitors

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Authors: Jamie W. Gittins, Kangkang Ge, Chloe J. Balhatchet, Pierre-Louis Taberna, Patrice Simon, Alexander C. Forse

Journal: Journal of the American Chemical Society

Abstract:

Layered metal–organic frameworks (MOFs) have emerged as promising materials for next-generation supercapacitors. Understanding how and why electrolyte ion size impacts electrochemical performance is crucial for developing improved MOF-based devices. To address this, we investigate the energy storage performance of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with a series of 1 M tetraalkylammonium tetrafluoroborate (TAABF4) electrolytes with different cation sizes. Three-electrode experiments show that Cu3(HHTP)2 exhibits an asymmetric charging response with all ion sizes, with higher energy storage upon positive charging and a greater charging asymmetry with larger TAA+ cations. The results further show that smaller TAA+ cations demonstrate superior capacitive performances upon both positive and negative charging compared to larger TAA+ cations. To gain further insights, electrochemical quartz crystal microbalance measurements were performed to probe ion electrosorption during charging and discharging. These reveal that Cu3(HHTP)2 has a cation-dominated charging mechanism, but interestingly indicate that the solvent also participates in the charging process with larger cations. Overall, the results of this study suggest that larger TAA+ cations saturate the pores of the Cu3(HHTP)2-based electrodes. This leads to more asymmetric charging behavior and forces solvent molecules to play a role in the charge storage mechanism. These findings significantly enhance our understanding of ion electrosorption in layered MOFs, and they will guide the design of improved MOF-based supercapacitors.

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Publication on AWSensors technology

Revisiting the Charging Mechanism of α-MnO2 in Mildly Acidic Aqueous Zinc Electrolytes

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Authors: Lang Yuan Wu, ZhiWei Li, YuXuan Xiang, WenDi Dong, XiaoDong Qi, ZhenXiao Ling, YingHong Xu, HaiYang Wu, Mikhael D. Levi, Netanel Shpigel, XiaoGang Zhang

Journal: Small 

Abstract: In recent years, there have been extensive debates regarding the charging mechanism of MnO2 cathodes in aqueous Zn electrolytes. The discussion centered on several key aspects including the identity of the charge carriers contributing to the overall capacity, the nature of the electrochemical process, and the role of the zinc hydroxy films that are reversibly formed during the charging/discharging. Intense studies are also devoted to understanding the effect of the Mn2+ additive on the performance of the cathodes. Nevertheless, it seems that a consistent explanation of the α-MnO2 charging mechanism is still lacking. To address this, a step-by-step analysis of the MnO2 cathodes is conducted. Valuable information is obtained by using in situ electrochemical quartz crystal microbalance with dissipation (EQCM-D) monitoring, supplemented by solid-state nuclear magnetic resonance (NMR), X-ray diffraction (XRD) in Characterization of Materials, and pH measurements. The findings indicate that the charging mechanism is dominated by the insertion of H3O+ ions, while no evidence of Zn2+ intercalation is found. The role of the Mn2+ additive in promoting the generation of protons by forming MnOOH, enhancing the stability of Zn/α-MnO2 batteries is thoroughly investigated. This work provides a comprehensive overview on the electrochemical and the chemical reactions associated with the α-MnO2 electrodes, and will pave the way for further development of aqueous cathodes for Zn-ion batteries.

 

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Publication on AWSensors technology

Study of the inhibition efficiency of DTPMPA on calcium carbonate formation via advanced tools

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Authors: Soumaya Nouigues, Nelson Acevedo, Yasser Ben Amor, Christel Laberty-Robert, Hubert Perrot, Hélène Cheap-Charpentier

Journal: Desalination

Abstract: The inhibition efficiency of a scale inhibitor, named diethylene triamine penta (methylene phosphonic acid) (DTPMPA), was evaluated using fast controlled precipitation (FCP) method, electrochemical quartz crystal microbalance (EQCM), quartz crystal microbalance with dissipation (QCM-D) and pre-scaled quartz crystal microbalance (SQCM). The results showed that DTPMPA delayed the CaCO3 precipitation and decreased the precipitation rate of the CaCO3 formation in solution and on a metallic surface, depending on the inhibitor concentration. In some cases, it could completely inhibit CaCO3 formation. CaCO3 precipitation was completely inhibited in solution and on a metallic surface in the presence of 0.5 mg⋅L−1 and 4 mg⋅L−1 DTPMPA, according to FCP and EQCM results, respectively. The morphology and composition of CaCO3 crystals formed were studied using SEM and XRD showing that the presence of the inhibitor promoted the formation of calcite. This is the first time that the influence of an organic inhibitor was studied using the combination of QCM methods, where the results revealed a reduction of the surface coverage by a CaCO3 layer as the inhibitor concentration increased. The activation energies were calculated in the presence of DTPMPA and indicated that the inhibitor retarded the scaling process.

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Publication on AWSensors technology

On the Electrochemical Activation of Nanoporous Reduced Graphene Oxide Electrodes Studied by In Situ/Operando Electrochemical Techniques

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Authors: María del Pilar Bernicola, Mailis Lounasvuori, Jessica Padilla-Pantoja, Jose Santiso, Catherine Debiemme-Chouvy, Hubert Perrot, Tristan Petit, Jose A. Garrido, Elena del Corro

Journal: Advanced Functional Materials

Abstract: Due to the difficult access of the electrolyte into the nanoconfined space of nanoporous reduced graphene oxide (rGO) electrodes, achieving the optimal electrochemical performance of these devices becomes a challenge. In this work, the dynamics of interfacial-governed phenomena are investigated during a voltage-controlled electrochemical activation of nanoporous rGO electrodes that leads to an enhanced electrochemical performance in terms of areal capacitance and electrochemical impedance. In situ/operando characterization techniques are used to reveal the dynamics of the irreversible material changes introduced during the activation process, including ionic diffusion and water confinement within the nanopores, along with the reduction of oxygenated groups and the decrease of the rGO interlayer distance. Furthermore, operando techniques are used to uncover the origin of the complex polarization-dependent dynamic response of rGO electrodes. The study reveals that the reversible protonation/deprotonation of remaining functional groups and the cation electro-adsorption/desorption process in the graphene basal plane govern the pseudocapacitive performance of nanoporous rGO electrodes. This work brings new understanding of the complex interplay between surface chemistry, ion confinement, and desolvation processes occurring during electrochemical cycling in nanoporous rGO electrodes, offering new insights for designing high-performing electrodes based on nanoporous rGO.

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Scientific publication

Hydrothermal vs. Electrochemical reduction of graphene oxide: A physico-chemical and quartz crystal microbalance study

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Authors: Caroline Keller, Gregory Barbillon, Catherine Debiemme-Chouvy, Ozlem Sel, Hubert Perrot

Journal: Carbon

Abstract

Reduced Graphene Oxide possesses numerous interesting properties, making it one of the most studied materials today. By this way, applications in various fields, including fundamental research, can be found. Nevertheless, the complexity of reduced Graphene Oxide lies in its fabrication process which defines their properties. In this paper, two fabrication methods -electrochemical and hydrothermal reduction of graphene oxide – were compared using physico-chemical and electrogravimetric analysis. Our findings reveal significant morphological differences between the two methods, accompanied by different electrochemical behaviors, when tested in aqueous electrolyte (i.e. 0.5 M Na2SO4). Specifically, electrochemically reduced graphene oxide exclusively involves sodium (whether hydrated or not) in its charge compensation mechanism, whereas hydrothermally reduced graphene oxide also involves proton in sodium sulfate solution.

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Scientific publication

Cation desolvation-induced capacitance enhancement in reduced graphene oxide (rGO)

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Authors: Kangkang Ge, Hui Shao, Encarnacion Raymundo-Piñero, Pierre-Louis Taberna & Patrice Simon

Journal: Nature Communications

Abstract

Understanding the local electrochemical processes is of key importance for efficient energy storage applications, including electrochemical double layer capacitors. In this work, we studied the charge storage mechanism of a model material – reduced graphene oxide (rGO) – in aqueous electrolyte using the combination of cavity micro-electrode, operando electrochemical quartz crystal microbalance (EQCM) and operando electrochemical dilatometry (ECD) tools. We evidence two regions with different charge storage mechanisms, depending on the cation-carbon interaction. Notably, under high cathodic polarization (region II), we report an important capacitance increase in Zn2+ containing electrolyte with minimum volume expansion, which is associated with Zn2+ desolvation resulting from strong electrostatic Zn2+-rGO interactions. These results highlight the significant role of ion-electrode interaction strength and cation desolvation in modulating the charging mechanisms, offering potential pathways for optimized capacitive energy storage. As a broader perspective, understanding confined electrochemical systems and the coupling between chemical, electrochemical and transport processes in confinement may open tremendous opportunities for energy, catalysis or water treatment applications in the future.

 

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Scientific publication

Robust battery interphases from dilute fluorinated cations

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Authors: Chulgi Nathan Hong, Mengwen Yan, Oleg Borodin, Travis P. Pollard, Langyuan Wu, Manuel Reiter, Dario Gomez Vazquez, Katharina Trapp , Ji Mun Yoo, Netanel Shpigel, Jeremy I. Feldblyum and Maria R. Lukatskaya

Journal: Energy Environ. Sci.

Abstract

Controlling solid electrolyte interphase (SEI) in batteries is crucial for their efficient cycling. Herein, we demonstrate an approach to enable robust battery performance that does not rely on high fractions of fluorinated species in electrolytes, thus substantially decreasing the environmental footprint and cost of high-energy batteries. In this approach, we use very low fractions of readily reducible fluorinated cations in electrolyte (∼0.1 wt%) and employ electrostatic attraction to generate a substantial population of these cations at the anode surface. As a result, we can form a robust fluorine-rich SEI that allows for dendrite-free deposition of dense Li and stable cycling of Li-metal full cells with high-voltage cathodes. Our approach represents a general strategy for delivering desired chemical species to battery anodes through electrostatic attraction while using minute amounts of additive.

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