Electrostatic Double Layer Research Articles

High cycling stability polyaniline/carbon sphere/graphene ternary nanocomposite cathode material for asymmetric supercapacitors

Here, an asymmetric supercapacitor of the ternary nanocomposite polyaniline/carbon sphere/graphene (PANI/CS/G) is developed through a green strategy via the in-situ polymerization of aniline in carbon sphere/graphene (CS/G) dispersion prepared in a ball-mill method coupled with hydrothermal treatment. A strong interaction and thus the coverage of CS/G with PANI is revealed from the material characterization using XRD, FTIR and Raman spectroscopic techniques, and also from FESEM and HRTEM images. Uniform distribution of PANI over the CS/G provided an effective conducting network and enhanced diffusion of the electrolyte ions. PANI/CS/G showed a specific capacitance of 145.02 mF/cm2 at a current density of 1 mA/cm2 in 1 M H2SO4 originating from the electrostatic double layer capacitance behavior of the CS/G and pseudocapacitance of PANI. The fabricated asymmetric coin cell device with PANI/CS/G cathode and CS/G anode showed the highest areal capacitance of 320.78 mF/cm2 (@ 1 mA/cm2), a maximum energy density of 18.99 Wh/kg (@ 0.21 A/g), and a highest power density of 6088.48 W/kg (@ 8.68 A/g). The device displayed 101.6 % capacitance retention after 10000 cycles, indicating the effect of CS/G in diminishing the volume changes of PANI during the charge-discharge process, which usually affects the cyclic stability. By lighting a green LED, the real sense energy storage application of the supercapacitor is evaluated.

(Invited) Application of Nanostructure for Improving the Interfacial Interactions between Sensing Surface and Targeted Particles

Various interfacial interactions, encompassing screened Coulomb (electrostatic double layer) forces, Lifshitz-van der Waals forces, hydrophobic/hydrophilic interactions, as well as steric, chemical, morphological, and roughness effects, have been confirmed to play a crucial role in governing the interaction between target particles and the sensing surface. Small protrusions on the sensing surface can induce substantial variations in the surface’s interaction with the target analytes based on the extended Derjauin-Landau-Verwey-Overbeek (DLVO) theory. 1 Here, indium tin oxide coated vertical nanowires served as nanostructure to investigate interfacial interactions between the sensing surface and targeted analytes. Analyzing the ratio of particle size to asperity size on the sensing surface within the extended DLVO theory revealed that surface roughness can provide sufficient interfacial interactions with target analytes, thereby enhancing the electrical sensing performance. Upon immersing the nanostructural sensing surface in an analyte solution, electrical signals undergo a significant shift owing to alterations in the surface potential at the interface between the functionalized sensing surface (such as antibodies or chemical functional groups) and the analyte solution. 2, 3 These observations highlight the critical role of nanostructure on the sensing surface, particularly with adequate surface roughness, in significantly improving sensing performance by facilitating effective interaction of the surface with the target analyte based on the extended DLVO theory.

Investigation of the surface charge behaviour of ettringite: Influence of pH, calcium, and sulphate ions

Ettringite is an important mineral that contributes to the overall performance of cementitious materials. Knowledge of the surface charge behaviour of a solid is necessary for a mechanistic description of surface processes such as adsorption or particle-particle interactions. The objective of this study was to develop a model capable of reproducing ettringite surface charge as a function of calcium, sulphate, and pH.Ettringite was synthesised and characterised using different analytical, microscopic, and spectroscopic techniques with the help of density functional theory. Electrophoretic mobility was measured using laser Doppler electrophoresis in alkaline waters representative of the cementitious environment.The behaviour of the ettringite surface charge was shown to be quite complex as sulphate and calcium acted in a competitive manner on the overall charge. The ζ-potential increases when the calcium content increases, whereas it decreases when sulphate increases. This is due to the possible adsorption of these ions at the surface, and the extent of the effect depends on the relative concentrations of Ca and SO42−.An electrostatic double layer model (DLM) was used to calculate the surface potential, considering the adsorption of both calcium and sulphate, as possible ions determining the potential (IDP), and formation of different complexes with ettringite surface functional groups (SOH). The variations of the ζ-potential could be satisfactorily predicted under the different chemical conditions of interest in a cementitious environment.

Electrostatic Correlations Lead to High Capacitance in Zwitterion-Containing Thin Films.

A novel zwitterion composed of an imidazolium tethered to an anionic sulfonyl(trifluoromethane sulfonyl)imide group was prepared as an alternative dielectric material to traditional ionic liquids. The zwitterion not only melted below 100 °C but also proved to be nonhygroscopic. High-capacitance organic dielectric materials were obtained by blending this compound with poly(methyl methacrylate) over a range of concentrations and thicknesses. Above a specific temperature and concentration, films exhibit a capacitance nearly equivalent to that of an electrostatic double layer, approximately 10 μF/cm2, regardless of their thickness. Grazing-incidence wide-angle X-ray scattering experiments suggest that the zwitterions adopt a lamellar ordering at their surface above a critical concentration. The observed ordering is correlated with a 1000-fold increase in capacitance. The behavior suggests that the zwitterions exhibit strong electrostatic correlations throughout the film bulk, pointing the way toward a novel class of organic dielectric materials.

Predicting thermodynamic adhesion energies of membrane fouling in planktonic anammox MBR via backpropagation neural network model

Predicting thermodynamic adhesion energies was a critical strategy for mitigating membrane fouling. This study utilized a backpropagation (BP) neural network model to predict the thermodynamic adhesion energies associated with membrane fouling in a planktonic anammox MBR. Acid-base (ΔGAB), electrostatic double layer (ΔGEL), and Lifshitz–van der Waals (ΔGLW) energies were selected as output variables, the training dataset was collected by the advanced Derjaguin-Landau-Verwey-Overbeek (XDLVO) method. Optimization results identified “7-10-3″ as the optimal network structure for the BP model. The prediction results demonstrated a high degree of fit between the predicted and experimental values of thermodynamic adhesion energy (R2 ≥ 0.9278), indicating a robust predictive capability of the model in this study. Overall, the study presented a practical BP neural network model for predicting thermodynamic adhesion energies, significantly enhancing the prediction tool for adhesive fouling behavior in anammox MBRs.

Bacterial surface properties and transport behavior actively respond to an extracellular polymeric substance gradient in saturated porous media

The transport and retention of bacteria in porous media, such as aquifer, are governed by the solid-liquid interface characteristics and bacterial mobility. The secretion of extracellular polymeric substance (EPS) by bacteria modifies their surface property, and thereby has effects on their adhesion to surface. The role of EPS in bacterial mobility within saturated quartz sand media is uncertain, as both promoting and inhibitory effects have been reported, and underlying mechanisms remain unclear. In this study, the effects of EPS on bacterial transport behavior and possible underlying mechanism were investigated at 4 concentrations (0 mg L−1, 50 mg L−1, 200 mg L−1 and 1000 mg L−1) using laboratory simulation experiments in conjunction with Extend Derjaguin-Landau-Verweu-Overbeek (XDLVO) modeling. The results showed that EPS facilitated bacterial mobility at all tested concentrations. It could be partially explained by the increased energy barrier between bacterial cells and quartz sand surface in the presence of EPS. The XDLVO sphere-plate model predicted that EPS induced a higher electrostatic double layer (EDL) repulsive force, Lewis acid-base (AB) and steric stabilization (ST), as well as a lower Lifshitz-van der Waals (LW) attractive force. However, at the highest EPS concentration (1000 mg L−1), the promotion of EPS on bacterial mobility weakened as a result of lower repulsive interactions between cells, which was supported by observed enhanced bacterial aggregation. Consequently, the increased aggregation led to greater bio-colloidal straining and ripening in the sand column, weakening the positive impact of EPS on bacterial transport. These findings suggested that EPS exhibited concentration-dependent effects on bacterial surface properties and transport behavior and revealed non-intuitive dual effects of EPS on those processes.

Anion Competition at Positively Charged Surfactant Monolayers.

Interactions of anions with hydrophobic surfaces of proteins and water-soluble polymers depend on the ability of the ions to shed their hydration shells. At positively charged surfactant monolayers, the interactions of anions are less well understood. Due to the interplay of electrostatic surface forces, hydration effects, and ion-ion interactions in the electrostatic double layer, a comprehensive microscopic picture remains elusive. Herein, we study the interactions of chloride, bromide, and a mixture of these two anions at the aqueous interface of dihexadecyldimethylammonium (DHDA+) and dioctadecyldimethylammonium (DODA+) cationic monolayers. Using molecular dynamics simulations and three surface-sensitive X-ray scattering techniques, we demonstrate that bromide interacts preferentially over chloride with both monolayers. The structure of the two monolayers and their interfacial electron density profiles obtained from the simulations quantitatively reproduce the experimental data. We observe that chloride and bromide form contact ion pairs with the quaternary ammonium groups on both monolayers. However, ion pairing with bromide leads to a greater reduction in the number of water molecules hydrating the anion, resulting in more energetically stable ion pairs. This leads to long-range (>3 nm) lateral correlations between bromide ions on the structured DODA+ monolayer. These observations indicate that ion hydration is the dominant factor determining the interfacial electrolyte structure.

Elevated temperature effects (T > 100 °C) on the interfacial water and microstructure swelling of Na-montmorillonite

Montmorillonite-based barriers are key elements of the engineered barrier systems (EBS) in geological disposal facilities (GDF). Their performance at temperatures above 100 °C is not sufficiently understood to assess the possibility of raising the temperature limits in GDF designs that could reduce construction costs and CO2 footprint. The present work provides new fundamental insights through molecular dynamics (MD) simulations of Na-montmorillonite's water-clay interactions and swelling pressure at temperatures 298–500 K and basal spacings of 1.5–3.5 nm. At temperatures above 100 °C, the swelling behaviour is governed by the attractive van der Waals force and the repulsive hydration force instead of the repulsive electrostatic (double layer) force. The swelling pressure reduction with increasing temperature is related to the weakened hydration repulsion and electric double layer repulsion, which result from the deterioration of the interlayer water layer structure and the shrinkage of the electric double layer. The applicability and breakdown of the classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory at elevated temperatures are examined. By excluding the osmotic contribution in the DLVO theory, the summation of the van der Waals interaction in DLVO and an additional non-DLVO hydration interaction can predict our MD system's swelling under high temperatures. The findings of this study provide a fundamental understanding of the swelling behaviour and the underlying molecular-level mechanisms of the clay microstructure under extreme conditions.

Ion correlation-driven like-charge attraction in multivalent salt solutions.

The electrostatic double layer force is key to determining the stability and self-assembly of charged colloids and many other soft matter systems. Fully understanding the attractive force between two like-charged surfaces remains a great challenge. Here, we apply the modified Gaussian renormalized fluctuation theory to study ion correlation-driven like-charge attraction in multivalent salt solutions. The effects of spatially varying ion correlations on the structure of overlapping double layers and their free energy are self-consistently accounted for. In the presence of multivalent salts, increasing surface charge or counterion valency leads to a short-range attraction. We demonstrate that although both overcharging and like-charge attraction are outcomes of ion correlation, there is no causal relationship between them. Our theory also captures the non-monotonic dependence of like-charge attraction on multivalent salt concentration. The reduction of attraction at high salt concentrations could be a contributing factor toward the reentrant stability of charged colloidal suspensions. Our theoretical predictions are consistent with the observations reported in experiments and simulations.

Depletion Type Organic Electrochemical Transistors and the Gradual Channel Approximation

AbstractThe gradual channel approximation forms the foundation for the analysis of field‐effect transistors. It has been used to discuss transistors that are not necessarily based on the field‐effect as well, such as the organic electrochemical transistor (OECT). Here, the applicability of the gradual channel approximation for OECTs is studied by a 2D drift‐diffusion model. It is found that OECT switching can be described by two separate effects—a doping/dedoping mechanism and the formation of an electrostatic double layer at the interface between the mixed conductor and the electrolyte. The balance between these two mechanisms is determined by the morphology of the mixed conductor, in particular the question if ions move in the same phase and electric potential as the holes, or if separate ion and hole phases are formed. It is argued that the gradual channel approximation can only be used to describe electrostatic switching at the mixed conductor/electrolyte interface (the two‐phase model), but cannot be employed to analyze devices operating on a doping/de‐doping mechanism (the one‐phase model).

A Survey of Strong Electric Potential Drops in the Ionosphere of Venus

AbstractEvery planet or moon with an ionosphere is thought to generate a weak electrical potential which helps ions overcome gravity and escape to space. A pilot study at Venus by Collinson et al. (2016, https://doi.org/10.1002/2016GL068327) indicated a planetary potential an order of magnitude stronger than expected. Here we present a statistical study of the electrical potential drop in the ionosphere of Venus, which was found to be an average of 7.04 ± 2.19 V. However, these strong potentials measured by Venus Express are likely atypical and extreme outliers associated with a transient phenomenon in the Venusian ionosphere. We posit they are associated with transient and sporadic density cavities in the ionosphere and may be the result of sporadic electrostatic double layer formation in the dayside ionosphere.

Deposition behaviors of carboxyl-modified polystyrene nanoplastics with goethite in aquatic environment: Effects of solution chemistry and organic macromolecules

The ubiquitous nanoplastics (NPs) in the environment are emerging contaminants due to their risks to human health and ecosystems. The interaction between NPs and minerals determines the environmental and ecological risks of NPs. In this study, the deposition behaviors of carboxyl modified polystyrene nanoplastics (COOH-PSNPs) with goethite (α-FeOOH) were systematically investigated under various solution chemistry and organic macromolecules (OMs) conditions (i.e., pH, ionic type, humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA)). The study found that electrostatic interactions dominated the interaction between COOH-PSNPs and goethite. The deposition rates of COOH-PSNPs decreased with an increase in solution pH, due to the enhanced electrostatic repulsion by higher pH. Introducing cations or anions could compress the electrostatic double layers and compete for interaction sites on COOH-PSNPs and goethite, thereby reducing the deposition rates of COOH-PSNPs. The stabilization effects, which were positive with ions valence, followed the orders of NaCl ≈ KCl < CaCl2, NaNO3 ≈ NaCl < Na2SO4 < Na3PO4. Specific adsorption of SO42− or H2PO4− caused a potential reversal of goethite from positive to negative, leading to the electrostatic forces between COOH-PSNPs and goethite changed from attraction to repulsion, and thus significantly decreasing deposition of COOH-PSNPs. Organic macromolecules could markedly inhibit the deposition of COOH-PSNPs with goethite because of enhanced electrostatic repulsion, steric hindrance, and competition of surface binding sites. The ability for inhibiting the deposition of COOH-PSNPs followed the sequence of SA > HA > BSA, which was related to their structure (SA: linear, semi-flexible, HA: globular, semi-rigid, BSA: globular, with protein tertiary structure) and surface charge density (SA > HA > BSA). The results of this study highlight the complexity of the interactions between NPs and minerals under different environments and provide valuable insights in understanding transport mechanisms and environmental fate of nanoplastics in aquatic environments.

Cd(II) adsorption on earth-abundant serpentine in aqueous environment: Role of interfacial ion specificity

Adsorption of heavy metal ions (e.g., Cd(II)) on clay minerals significantly affects their transport and fate in natural and engineered waterbodies. To date, the role of interfacial ion specificity in the adsorption of Cd(II) on earth-abundant serpentine remains elusive. In this work, the adsorption of Cd(II) on serpentine at typical environment conditions (pH 4.5–5.0), particularly under the complex influence of common environmental anions (e.g., NO3−, SO42−) and cations (e.g., K+, Ca2+, Fe3+, Al3+) was systemically investigated. It was found that the adsorption of Cd(II) on serpentine surface due to the inner-sphere complexation could be negligibly affected by the anion type, yet the cations specifically modulated the Cd(II) adsorption. The presence of mono- and divalent cations moderately enhanced the Cd(II) adsorption by weakening the electrostatic double layer (EDL) repulsion between Cd(II) and Mg–O plane of serpentine, while trivalent cations significantly suppressed the adsorption of Cd(II) due to the competitive adsorption. Based on the spectroscopy analysis, Fe3+ and Al3+ were found to robustly bind the surface active sites of serpentine, thereby preventing the inner-sphere adsorption of Cd(II). The density functional theory (DFT) calculation indicated that Fe(III) and Al(III) exhibited the larger adsorption energy (Ead = −146.1 and −516.1 kcal mol−1, respectively) and stronger electron transfer capacity with serpentine compared to Cd(II) (Ead = −118.1 kcal mol−1), thus resulting in the formation of more stable Fe(III)–O and Al(III)–O inner-sphere complexes. This study provides valuable insights into the influence of interfacial ion specificity on the Cd(II) adsorption in terrestrial and aquatic environments.

Effect of cholesterol on the ion-membrane interaction: Zeta potential and dynamic light scattering study

Cholesterol in a bio-membrane plays a significant role in many cellular event and is known to regulate the functional activity of protein and ion channel. In this study we report a significant effect of cholesterol on the ion-membrane interaction. We prepare large unilamellar vesicles, composed of zwitterionic lipid DOPC and anionic lipid DOPG with different cholesterol concentration. Electrostatics of anionic membranes containing cholesterol in the presence of NaCl has systematically been explored using dynamic light scattering and zeta potential. Negative zeta potential of the membrane decreases its negative value with increasing ion concentration for all cholesterol concentrations. However, zeta potential itself decreases with increasing cholesterol content even in the absence of monovalent ions. Electrostatic behaviour of the membrane is determined from well-known Gouy Chapmann model. Negative surface charge density of the membrane decreases with increasing cholesterol content. Binding constant, estimated from the electrostatic double layer theory, is found to increase significantly in the presence of cholesterol. Comparison of electrostatic parameters of the membrane in the presence and absence of cholesterol suggests that cholesterol significantly alter the electrostatic behaviour of the membrane.

Insights into the membrane biofouling behavior of planktonic anammox bacteria: Effect of solution pH and ionic strength

Understanding the effect of solution pH and ionic strength on membrane biofouling of anammox bacteria is essential for the widespread application of anammox MBRs. To provide an original elucidation, this study combined interfacial thermodynamics analysis and filtration experiments with an established planktonic anammox MBR to explore the biofouling behavior of anammox bacteria under varying solution pH and ionic strengths. Preliminary results showed that variation in solution pH and ionic strength has critical impacts on the thermodynamic properties of planktonic anammox bacteria and membrane surfaces. The further interfacial thermodynamics analysis and filtration experiments indicated that an increased pH and a decreased ionic strength could reduce membrane fouling by planktonic anammox bacteria. More specifically, a higher pH or lower ionic strength resulted in a stronger repulsive energy barrier due to the larger interaction distance covered by the dominant electrostatic double layer (EL) component compared to the Lewis acid-base (AB) and Lifshitz–van der Waals (LW) components, which corresponded to a reduction in the normalized flux (J/J0) decline and the accumulation of cake resistance (Rc) during the filtration process. Furthermore, the aforementioned effect mechanism was verified by a correlation analysis of the thermodynamic properties and filtration behavior. These findings have generalized significance for understanding the biofouling or aggregation behavior of anammox bacteria.

Treatment of simulated saline brine water by membrane distillation process enhanced through alternating current electric field

Treatment of saline brine has been a tricky challenge in recent years, and membrane distillation (MD) is considered as a promising alternative technology. But it was found that the normalized flux significantly decreased to 0.6 within 15 h when treating simulated salinity brine, which was caused by the deposition of the humic acids (HA), CaSO4, and HA-Ca complex, suggesting the severe membrane fouling. In this study, a composite membrane was fabricated by coating carbon nanotubes (CNT) on the commercial PTFE membrane, and an alternating current (AC) electric field was subsequently applied that aimed to improve MD performance. Specially, the application of 50 Hz square wave dramatically retarded the inorganic fouling and the intensity of membrane organic matter was reduced by 60.6% due to its hydrophilic surface and instantaneous polarity conversion, thus its normalized flux even maintained around 0.9 after 15 h operation. Coupled with the modified XDLVO analysis, the coating CNT layer exhibited good resistance of HA due to their electrostatic repulsions, both of which carried a strong negative charge and high density hydrophilic functional groups. It was also found that except the movement distance of charged substances far greater than the thickness of the fixed electrostatic double layer, AC electric field with certain frequency significantly reduced the coexistence time for substances with opposite charge by keeping them in motion that could further alleviate the fouling. This study suggested that a hybrid system of AC electric field and MD would provide a potential alternative for treating the salinity brine water.

Acid‐Based Polymer Gel as an Efficient Electrolyte

Present studies basically focused on preparation a system by using polymer which can show high value of conductivity and can be used as an efficient electrolyte in the formation of electrostatic double layer capacitor cell (EDLC). Here, polyvinylpyrrolidone (PVP) polymer-H2SO4 acid-based electrolyte system have been synthesized. H2SO4 as acid is diluted using double distilled (DD) water for maximum conductivity. Various wt% of PVP as polymer added in optimized H2SO4 (1.0 M). Different types of electrical studies such as: electrical conductivity, dielectric analysis, potential window stability have been analyzed for good results. Selected system (PVP-H2SO4) shows highest conductivity in the range ≈10−1 S cm−1.

Effects of biofilms on the retention and transport of PFOA in saturated porous media.

Understanding the fate and transport of perfluorooctanoic acid (PFOA) in soil and groundwater is essential to reliable assessments of its risks. This study investigated the impacts of Gram-positive Bacillus subtilis (BS), Gram-negative Pseudomonas aeruginosa (PA) and wild microbiota (WM) biofilm on the transport of PFOA in saturated sand columns at two ionic strengths (i.e., 1.0 and 20.0mM NaCl). The retention of PFOA in biofilm-coated sand columns was higher than that in uncoated sand columns, due to biofilm-induced reinforced hydrophobic interactions and surface roughness, and decreased zeta potential. However, the retention effects varied among biofilm bacterial species with PFOA retardation factors in PA, WM and BS columns of 1.29-1.38, 1.21-1.29 and 1.11-1.15, respectively. Notably, PA biofilm had the most pronounced effect on PFOA retention. While increasing ionic strength promoted the retention of PFOA in BS biofilm-coated sand, it had no significant impact on PFOA transport in PA and WM biofilm-coated sand. This could be attributed to the differences in biofilm composition, deviating the ionic strengths effects on electrostatic double layer compression. The advection dispersion equation coupled with two-site kinetic retention model well described the transport of PFOA in all saturated columns. Our findings reveal that biofilm plays important roles in PFOA transport in porous media, instructive for risk assessment and remediation of PFOA contamination.

Effect of decoration route on the nanomechanical, adhesive, and force response of nanocelluloses-An in situ force spectroscopy study.

Although cellulose derivatives are widely applied in high-tech materials, the relation between their force responses and their surface chemical properties in a biological environment as a function of pH is unknown. Here, interaction forces of surface modified cellulose nanocrystals (CNCs), lignin residual cellulose nanocrystals (LCNCs), and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibres (TCNFs) with OSO3-, COO- and lignin chemical groups were measured using in situ peak force quantitative nanomechanical mapping and force spectroscopy in salt solution at two pH values. We found that the forces acting between the tip and CNC or LCNC are steric dominated showing long range and slow decay as a result of their low surface charge density. High Mw lignin contributed to the increased repulsion range for LCNCs compared to CNCs. The repulsion measured for TCNFs at the very short range was electrostatic force dominating showing a steep decay attributed to its high surface charge density. In the case of TCNFs, electrostatic double layer force was also evidenced by the attraction measured at secondary minima. In all the three cases the electro steric interactions are pH dependent. Dissipation maps verified that the force behavior for each material was related to structural conformation restriction of the groups at compression. The slow decayed repulsion of CNCs or LCNCs is related to a weak restriction of conformational change due to small surface groups or high molecular weight bound polymers forming flat layers, whereas the steep repulsion of TCNFs is attributed to a strong conformation restriction of carboxylic groups occurred by forming extended structure. Our results suggest that the force responses of the materials were dominated by surface charges and structural differences. TCNFs showed superior nanomechanical and repulsion properties over CNCs or LCNCs at neutral pH.

Double Layers in the Earth's Bow Shock

AbstractWe present Magnetospheric Multiscale observations of electrostatic double layers in quasi‐perpendicular Earth's bow shock. These double layers have predominantly parallel electric field with amplitudes up to 100 mV/m, spatial widths of 50–700 m, and plasma frame speeds within 100 km/s. The potential drop across a single double layer is 2%–7% of the cross‐shock potential in the de Hoffmann‐Teller frame and occurs over the spatial scale of 10 Debye lengths or one tenth of electron inertial length. Some double layers can have spatial width of 70 Debye lengths and potential drop up to 30% of the cross‐shock potential. The electron temperature variation observed across double layers is roughly consistent with their potential drop. While electron heating in the Earth's bow shock occurs predominantly due to the quasi‐static electric field in the de Hoffmann‐Teller frame, these observations show that electron temperature can also increase across Debye‐scale electrostatic structures.