Solid Electrodes Research Articles

Crystalline Electrolyte Boosts High Performance of All-Solid-State Lithium-Ion Batteries.

The rigid solid-solid contact at the interface between the solid electrolyte and electrodes in full-solid-state lithium-ion batteries (ASSBs) presents a considerable challenge to lithium ion transport. To address this, we propose using Li-concentrated succinonitrile (Li-SN45) as an efficient bilateral interface modifier in ASSBs. This material boasts exceptional ionic conductivity of 3.38 mS cm-1 and excellent corrosion resistance to the Li metal anode. The assembled ASSBs using layered cathodes and Li metal demonstrate outstanding discharge capacity (170 mAh g-1 @ 20 mA g-1) and superior long-term cycling performance (97% capacity retention after 100 cycles). MALDI-TOF results suggest the formation of a crystalline structure in Li-SN45, which facilitates smooth "anion-free" Li+ hopping paths assisted by the oxygen atoms, as revealed by the solved crystal structure. Our findings enriched the understanding of Li transport dynamics in electrolytes of ASSBs, paving the way to designing superior next-generation ASSBs with fast Li transport.

Multifunctional Nanocomposite Polymer‐integrated Ca‐doped CeO2 Electrolyte for Robust and High‐rate All‐solid‐state Sodium‐ion Batteries

AbstractDue to the seamless interfaces between solid polymer electrolytes (SPEs) and electrode materials, SPEs‐based all‐solid‐state sodium‐ion batteries (ASSSIBs) are considered promising energy storage systems. However, the sluggish Na+ transport and uncontrollable Na dendrite propagation still hinder the practical application of SPEs‐based ASSSIBs. Herein, Ca‐doped CeO2 (Ca−CeO2) nanotube framework is synthesized and integrated with poly (ethylene oxide) methyl ether acrylate‐perfluoropolyether copolymer (PEOA‐PFPE), resulting in multifunctional solid nanocomposite electrolytes (namely SNEs, i.e., PEOA‐PFPE/Ca−CeO2). Our investigations demonstrate that the fluorous effect incurred by the fluorine‐containing PEOA‐PFPE and the oxygen vacancy effect induced by the Ca−CeO2 framework could synergistically promote the dissociation of sodium salt, ultimately enhancing the Na+ mobility in SNEs. Besides, the resultant SNEs construct rapid Na+ transport channels and homogenize the Na deposition in SNEs/Na interface, which effectively prevents the Na dendrite growth. Furthermore, the assembled carbon‐coated sodium vanadium phosphate (NVP@C)||PEOA‐PFPE/Ca−CeO2||Na coin cell delivers impressive rate capability of 97.9 mAh g−1 at 2 C and outstanding cycling stability with capacity retention of 84.3 % after 300 cycles at 1 C. This work illustrates that constructing multifunctional SNEs via incorporating functional inorganic frameworks into fluorine‐containing SPEs could be a promising strategy for the commercialization of robust and high‐performance ASSSIBs.

A Monte Carlo Approach for Simulating Electrical Conductivity in Highly Porous Ceramic Composites: Impact of Internal Structure.

Porous ceramic composites play an important role in several applications. This is due to their unique properties resulting from a combination of various materials. Determination of the composite properties and structure is crucial for their further development and optimization. However, composite analysis often requires complex, expensive, and time-demanding experimental work. Mathematical modeling represents an effective tool to substitute experimental approach. The present study employs a Monte Carlo 3D equivalent electronic circuit network model developed to analyze a highly porous composite on the basis of minimum easily obtainable input parameters. Solid oxide cell electrodes were used as a model example, and this study focuses primarily on materials with a porosity of 55% and higher, characterized by deviation of behavior from those of lower void fraction share. This task is approached by adding to the original Monte Carlo model an additional parameter defining the void phase coalescence phenomenon. The enhanced model accurately simulates electrical conductivity for experimental samples of up to 75% porosity. Using sample composition, single-phase properties, and experimentally determined conductivity, this model allows us to estimate data of the internal structure of the material. This approach offers a rapid and cost-effective method to study material microstructure, providing insights into properties, such as electrical conductivity and heat conductivity. The present research thus contributes to advancing predictive capabilities in understanding and optimizing the performance of composite materials with potential in various technological applications.

Tailored Design of a Nanoporous Structure Suitable for Thick Si Electrodes on a Stiff Oxide-Based Solid Electrolyte.

Oxide-based all-solid-state batteries are ideal next-generation batteries that combine high energy density and high safety, but their realization requires the development of interface bonding technology between the stiff solid electrolyte and electrode. Even if the interface could be bonded, it is difficult to hold the interface, because only the electrode expands/contracts unilaterally during charge/discharge reactions. In particular, silicon (Si), which has eagerly awaited as a next-generation negative-electrode material for many years, changes in volume by several hundred percent. To solve these problems, in this work, highly porous silicon oxide (SiOx) electrodes with different porous structures were fabricated on a stiff garnet-type Li7La3Zr2O12 solid electrolyte, the three-dimensional nanoporous structure was analyzed quantitatively, and the charge/discharge characteristics were investigated. The microscopic observation and electrochemical analysis revealed how we should control the porous structure, such as sizes of pores and SiOx, size distribution, and porosity, for repeated and stable charge/discharge cycles. In addition, the resultant porous SiOx electrodes demonstrated superior charge/discharge cycle performance even when it thickened to 5 μm, whereas non-porous SiOx easily peeled off from the solid electrolyte when its thickness exceeded 0.1 μm. The thick SiOx films greatly improved the energy density per unit area (mAh cm-2). Nanosized fine pores with an interconnected open-pore architecture effectively mitigated the internal and interfacial stress upon expansion (charge)/contraction (discharge) of Si, and as a result, the thick and porous SiOx electrode maintained the interfacial joint with the stiff solid electrolyte after repeated charge/discharge cycles. These results will provide useful insights for effectively designing more practical porous SiOx powder effectively.

Electrical Double Layer Spillover Drives Coupled Electron- and Phase-Transfer Reactions at Electrode/Toluene/Water Three-Phase Interfaces.

A mechanism for the concerted pathway of coupled electron- and phase-transfer reactions (CEPhT) is proposed. CEPhT at three-phase interfaces formed by a solid electrode, an insulating organic solvent, and an aqueous electrolyte is driven by electric double layer (EDL) spillover, with significant electrostatic potential gradients extending a few nanometers into the insulating phase. This EDL spillover phenomenon is studied using scanning electrochemical cell microscopy to interrogate the oxidation of ferrocene in toluene to ferrocenium in water, (Fc)tol → (Fc+)aq + e-. Finite element method simulations of the electrostatic potential distribution and species concentration profiles enable the calculation of complete i-E curves that incorporate mass transport, electron transfer, phase transfer, and the EDL structure. Simulated and experimental i-E traces show good agreement in the current magnitude and the effect of the supporting electrolyte, identifying an unexpected dependence of overall reaction kinetics on the concentration of the supporting electrolyte in the aqueous phase due to EDL spillover. An interfacial toluene/water mixing region generates a unique electrochemical microenvironment where concerted electron transfer and solvent shell replacement facilitate CEPhT. Kinetic expressions for concerted and sequential CEPhT mechanisms highlight the role of this interfacial environment in controlling the rate of CEPhT. These combined experimental and simulated results are the first to support a concerted mechanism for CEPhT where (Fc)tol is transported to the interfacial mixing region at the three-phase interface, where it undergoes oxidation and phase transfer. EDL spillover can be leveraged for engineering sample geometries and electrostatic microenvironments to drive electrochemical reactivity in classically forbidden regions, e.g., insulating solvents and gases.

Low-temperature Deposited Highly Sensitive Integrated All-Solid Electrodes for Electrochemical pH Detection

This article describes the process of fabricating an integrated all-solid electrode (IASE) by integrating thin films of titanium dioxide (TiO<i>2</i>) and silver/silver chloride (Ag/AgCl) onto an indium tin oxide (ITO) substrate. The fabrication of a pH sensing electrode (SE) involved utilizing a spin-coated thin film composed of TiO<i>2</i>. Thermally produced thin films of Ag/AgCl were used to develop solid reference electrodes (RE). The present work examined the impact of the drying process on the pH sensitivity and linearity of the low-temperature deposited IASE. The drying procedure was carried out within a temperature range from room temperature to 100°C. The investigation involved the examination of crystallinity, surface morphology, and thin film composition through the utilization of field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX) methods. In addition, a comparison was made between the pH sensing performance of the IASE and a commercially available Ag/AgCl RE. The findings of this research demonstrate that the IASE sample, which underwent a drying process at a temperature of 100°C, exhibited remarkable sensitivity and linearity values of 66.7 mV/pH and 0.9827, separately, when compared to the commercially available RE.

Accessing Elastic Properties of Porous Solid Oxide Fuel Cell Electrodes Using 2D Image-Based Discrete Element Modeling and Deep Learning

Accessing Elastic Properties of Porous Solid Oxide Fuel Cell Electrodes Using 2D Image-Based Discrete Element Modeling and Deep Learning

Multifunctional Nanocomposite Polymer-integrated Ca-doped CeO2 Electrolyte for Robust and High-rate All-solid-state Sodium-ion Batteries.

Due to the seamless interfaces between solid polymer electrolytes (SPEs) and electrode materials, SPEs-based all-solid-state sodium-ion batteries (ASSSIBs) are considered promising energy storage systems. However, the sluggish Na+ transport and uncontrollable Na dendrite propagation still hinder the practical application of SPEs-based ASSSIBs. Herein, Ca-doped CeO2 (Ca-CeO2) nanotube framework is synthesized and integrated with poly (ethylene oxide) methyl ether acrylate-perfluoropolyether copolymer (PEOA-PFPE), resulting in multifunctional solid nanocomposite electrolytes (namely SNEs, i.e., PEOA-PFPE/Ca-CeO2). Our investigations demonstrate that the fluorous effect incurred by the fluorine-containing PEOA-PFPE and the oxygen vacancy effect induced by the Ca-CeO2 framework could synergistically promote the dissociation of sodium salt, ultimately enhancing the Na+ mobility in SNEs. Besides, the resultant SNEs construct rapid Na+ transport channels and homogenize the Na deposition in SNEs/Na interface, which effectively prevents the Na dendrite growth. Furthermore, the assembled carbon-coated sodium vanadium phosphate (NVP@C)||PEOA-PFPE/Ca-CeO2||Na coin cell delivers impressive rate capability of 97.9 mA h g-1 at 2 C and outstanding cycling stability with capacity retention of 84.3% after 300 cycles at 1 C. This work illustrates that constructing multifunctional SNEs via incorporating functional inorganic frameworks into fluorine-containing SPEs could be a promising strategy for the commercialization of robust and high-performance ASSSIBs.

Mechanistic Insights into the Potentiodynamic Electrosynthesis of PEDOT Thin Films at a Polarizable Liquid|Liquid Interface.

Conducting polymer (CP) thin films find widespread use, for example in bioelectronic, energy harvesting and storage, and drug delivery technology. Electrosynthesis at a polarizable liquid|liquid interface using an aqueous oxidant and organic soluble monomer provides a route to free-standing and scalable CP thin films, such as poly(3,4-ethylenedioxythiophene) (PEDOT), in a single step at ambient conditions. Here, using the potentiodynamic technique of cyclic voltammetry, interfacial electrosynthesis involving ion exchange, electron transfer, and proton adsorption charge transfer processes is shown to be mechanistically distinct from CP electropolymerization at a solid electrode|electrolyte interface. During interfacial electrosynthesis, the applied interfacial Galvani potential difference controls the interfacial concentration of the oxidant, but not the CP redox state. Nevertheless, typical CP electropolymerization electrochemical behaviors, such as steady charge accumulation with each successive cycle and the appearance of a nucleation loop, were observed. By combining (spectro)electrochemical measurements and theoretical models, this work identifies the underlying mechanistic origin of each feature on the cyclic voltammograms (CVs) due to charge accumulated from Faradaic and capacitive processes as the PEDOT thin film grows. To prevent overoxidation during interfacial electrosynthesis with a powerful cerium aqueous oxidant, scan rates in excess 25 mV·s-1 were optimal. The experimental methodology and theoretical models outlined in this article provide a broadly generic framework to understand evolving CVs during interfacial electrosynthesis using any suitable oxidant/monomer combination.

Influence of Conductive Additives and Binder on the Impedance of Lithium-Ion Battery Electrodes: Effect of an Inhomogeneous Distribution

The conductive additive and binder domain (CBD) is an essential component of lithium-ion battery electrodes. It enhances the electrical connectivity and mechanical stability within the solid electrode matrix. Migration of the binder during electrode drying can lead to an inhomogeneous distribution of the CBD, impeding transport of lithium ions into the electrodes, and diminishing the electronic pathways between solid particles and the current collector. This is especially prominent in thick electrodes at high drying rates. Therefore, we investigate the effect of a non-uniform CBD distribution on the electrochemical performance of NMC622 electrodes via microstructure-resolved three-dimensional (3D) simulations on virtual electrodes, based on tomographic image data, and compare them with experimental results. The valuable information derived by combining microstructure-resolved models with electrochemical impedance spectroscopy measurements on symmetric cells under blocking electrolyte conditions is used to characterize the lithium-ion transport in the electrode pore space, including the contributions of the CBD. The effect of this inhomogeneity on electrode performance is then gauged via galvanostatic discharge simulations under changing discharge currents and for varying electrode densities. Through our work, we demonstrate the significance of the CBD distribution and enable predictive simulations for future battery design.

3D-Printed Transducers for Solid Contact Potentiometric Ion Sensors: Improving Reproducibility by Fabrication Automation.

3D printing technology has become attractive in the development of electrochemical sensors as it offers automation in fabrication, customization on-demand, and reproducibility, among other features. Nonetheless, to date, solid contact potentiometric ion sensors have remained overlooked using this technology. Thus, the novelty of this work relies on demonstrating for the first time the usefulness of the multimaterial 3D printing approach to manufacture potentiometric ion-selective electrodes. The significance is indeed twofold. First, we discovered that by using the polyethylene terephthalate glycol (PETg) and polylactic acid-carbon black (PLA-CB) filaments together with a rational electrode design containing a well to accommodate the ion-selective membrane, a tight seal among all of the sensing materials is obtained. Importantly, this has mainly impacted the electrode-to-electrode reproducibility (ERSD0 ± 3 mV). Second, 75 ready-to-use electrodes can be printed in less than 3.5 h in a completely automated manner at a cost of ∼0.32 €/sensor. This feature may positively impact the suitability of further scaled-up production as well as the possibility of application in low-resource contexts. Overall, the presented outcomes are expected to encourage certain research directions to adopt using multimaterial 3D-printing approaches for producing highly reproducible solid contact potentiometric ion-selective electrodes, but are not restricted to them.

Unveiling crystal orientation-dependent interface property in composite cathodes for solid-state batteries by in situ microscopic probe

A critical bottleneck toward all-solid-state batteries lies in how the solid(electrode)-solid(electrolyte) interface is fabricated and maintained over repeated cycles. Conventional composite cathodes, with crystallographically distinct electrode/electrolyte interfaces of random particles, create complexities with varying (electro)chemical compatibilities. To address this, we employ an epitaxial model system where the crystal orientations of cathode and solid electrolyte are precisely controlled, and probe the interfaces in real-time during co-sintering by in situ electron microscopy. The interfacial reaction is highly dependent on crystal orientation/alignment, especially the availability of open ion channels. Interfaces bearing open ion paths of NCM are more susceptible to interdiffusion, but stabilize with the early formed passivation layer. Conversely, interfaces with closed ion pathway exhibit stability at intermediate temperatures, but deteriorate rapidly at high temperature due to oxygen evolution, increasing interfacial resistance. The elucidation of these distinct interfacial behaviors emphasizes the need for decoupling collective interfacial properties to enable rational design in solid-state batteries.

Phase transformation concurrent to charge storage governing electrochemical thermopower in amorphous and crystalline V2O5

Under urgent threat of global climate change, pressing need for efficient energy harvesting solutions exists. Electrochemical waste heat harvesting using solid electrodes offers a promising potential due to its high energy density. Yet, strategies for enhancing electrochemical thermopower in solid electrodes remain unidentified. Here, we investigate the LixV2O5 material system with controllably differentiated charge storage mechanisms and phase change behaviors. We show that concurrent phase transitions during lithiation significantly enhance the electrochemical thermopower to 1.04 mV/K, compared to 0.14 mV/K without phase transition. This discovery provides valuable insights into enhancing electrochemical thermopower for improved efficiency, underscoring the importance of mechanisms that facilitate entropy exchange, as demonstrated by the phase transformations.

Correlating the structure of quinone-functionalized carbons with electrochemical CO2 capture performance

Electrochemical carbon dioxide capture is emerging as an energy-efficient alternative to traditional carbon capture technology. In particular, redox-active molecules that can capture carbon dioxide when electrochemically reduced and release carbon dioxide when electrochemically re-oxidized are under active development. To prepare a carbon capture device, these molecules can be incorporated into a solid electrode in a battery-like cell. In this work, we explore the scope of a recently developed method where anthraquinones are covalently attached to porous carbon supports to obtain electrodes for electrochemical carbon dioxide capture. We functionalize four different porous carbon materials with varying porosities and surface chemistries, and use gas sorption analysis and solid-state NMR spectroscopy to probe the location of the grafted anthraquinones. All four functionalized materials show electrochemically mediated capture and release of carbon dioxide, and we explore the factors that determine their performance. While the anthraquinone-functionalized mesoporous carbon, f-CMK-3, showed the highest quinone loading, it showed poor quinone utilization for CO2 capture and poor long-term cycling stability. In contrast, the predominantly microporous functionalized carbon, f-YP-80F, showed a higher quinone utilization and improved cycling stability. This work can guide the design of functionalized carbon electrodes for electrochemical carbon dioxide capture.

Carbon Steel Corrosion Induced by Sulfate-Reducing Bacteria: A Review of Electrochemical Mechanisms and Pathways in Biofilms

Microbial metal corrosion has become an important topic in metal research, which is one of the main causes of equipment damage, energy loss, and economic loss. At present, the research on microbial metal corrosion focuses on the characteristics of corrosion products, the environmental conditions affecting corrosion, and the measures and means of corrosion prevention, etc. In contrast, the main microbial taxa involved in metal corrosion, their specific role in the corrosion process, and the electron transfer pathway research are relatively small. This paper summarizes the mechanism of microbial carbon steel corrosion caused by SRB, including the cathodic depolarization theory, acid metabolite corrosion theory, and the biocatalytic cathodic sulfate reduction mechanism. Based on the reversible nature of electron transfer in biofilms and the fact that electrons must pass through the extracellular polymers layer between the solid electrode and the cell, this paper focuses on three types of electrochemical mechanisms and electron transfer modes of extracellular electron transfer occurring in microbial fuel cells, including direct-contact electron transfer, electron transfer by conductive bacterial hair proteins or nanowires, and electron shuttling mediated by the use of soluble electron mediators. Finally, a more complete pathway of electron transfer in microbial carbon steel corrosion due to SRB is presented: an electron goes from the metal anode, through the extracellular polymer layer, the extracellular membrane, the periplasm, and the intracellular membrane, to reach the cytoplasm for sulfate allosteric reduction. This article also focuses on a variety of complex components in the extracellular polymer layer, such as extracellular DNA, quinoline humic acid, iron sulfide (FeSX), Fe3+, etc., which may act as an extracellular electron donor to provide electrons for the SRB intracellular electron transfer chain; the bioinduced mineralization that occurs in the SRB biofilm can inhibit metal corrosion, and it can be used for the development of green corrosion inhibitors. This provides theoretical guidance for the diagnosis, prediction, and prevention of microbial metal corrosion.

Impact of functional groups on lithium salt dispersion and mobility in polymer electrolytes

AbstractSolid Polymer electrolytes are versatile, highly processible and electrochemically compatible with solid electrode materials. The versatility of these materials is a result of the existence of many possible conductive polymer‐salt, polymer‐polymer and salt‐salt combinations. Despite the wide array of available lithium salts, most polymer electrolyte materials are made using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) due to its long history of achieving relatively high ionic conductivities in polymer electrolyte systems with the most famous being poly(ethylene oxide) (PEO). It is however possible that better ionic conductivities can be achieved with different salts and/or in polymer matrices containing different functional groups. This is because ionic conductivity in polymer electrolytes is partially based on the ability of the polymer matrix to dissolve and bond to the salt. These interactions impact local‐scale ion mobility which can be measured via NMR spectroscopy using pulsed field gradient experiments. In this work, polymer electrolytes are prepared using PEO, hydrogenated nitrile butadiene rubber and poly(propylene) carbonate. Ion mobility, lithium conductivity and salt‐polymer interactions are investigated to compare interactions between LiTFSI and lithium cyano(trifluorosulfonyl)imide in polymers with common salt‐dissociating functional groups such as ethyl, nitrile and carbonate to determine the impact of these interactions on ionic conductivity.

A Transparent, Patternable, and Stretchable Conducting Polymer Solid Electrode for Dielectric Elastomer Actuators

AbstractDielectric elastomer actuators (DEAs) offer versatile applications including haptics, soft robotics and smart lenses. However, due to the lack of conductive electrodes with low modulus and high stretchability, their use is limited by nonsolid electrodes, hindering integration with other systems. In this study, transparent and patternable solid electrodes, achieving actuation performance comparable to a commonly used non‐solid counterpart (e.g., carbon grease), with a stretchable and patternable conducting polymer composed of PEDOT:PSS and PEG‐PPG‐PEG diacrylate (P123DA) are reported. Varying the ratio of P123DA to PEDOT:PSS enables optimization of electrical and mechanical properties to achieve compliant solid electrodes in static and dynamic actuation. The ratio of P123DA to PEDOT:PSS is found to impact PEDOT:PSS nanofiber formation and the associated electrical and mechanical properties. Moreover, the resulting P123DA/PEDOT:PSS‐based solid electrode shows excellent optical transmittance exceeding 95%. This work highlights the potential of tuning different solid electrode properties to realize transparent, patternable, and stretchable solid electrodes, enhancing their applicability in diverse fields.

Synthesis of Porous Carbon Honeycomb Structures Derived from Hemp for Hybrid Supercapacitors with Improved Electrochemistry.

Energy storage in electrochemical hybrid capacitors involves fast faradaic reactions such as an intercalation, or redox process occurring at a solid electrode surface at an appropriate potential. Hybrid sodium-ion electrochemical capacitors bring the advantages of both the high specific power of capacitors and the high specific energy of batteries, where activated carbon serves as a critical electrode material. Herein, we have demonstrated that a porous honeycomb structure activated carbon derived from Australian hemp hurd (Cannabis sativa L.) in aqueous Na2SO4 electrolyte showed a specific capacitance of 240 F/g at 1 A/g.The hybrid sodium-ion device employing hemp-derived activated carbon (HAC) coupled with electrolytic manganese dioxide (EMD) in an aqueous Na2SO4 electrolyte showed a specific capacitance of 95 F/g at 1 A/g having a capacitance retention of 90%. The hybrid device (HAC||EMD) can possess excellent electrochemical performance metrics, having a high energy density of 38 Wh/kg at a power density of 761 W/kg. Overall, this study provides insights into the influence of the activation temperature and the KOH impregnation ratio on morphology, porosity distribution, and the activated carbon's electrochemical properties with faster kinetics. The high cell voltage for the device is devoted to the EMD electrode.

Experimental study of ECDM using a porous electrode containing internal micropores

ABSTRACT In electrochemical discharge machining (ECDM), continuous renewal of electrolyte between the tool electrode and the workpiece guarantees stable discharge machining. Proposed in this paper is Porous-electrode ECDM (p-ECDM) using a tool electrode made of porous material containing micrometer pores. The rough surface of the porous electrode promotes electrolyte regeneration between the electrodes to produce a stable and relatively thin gas film. At the same time, the internal connected micropores are used to provide controlled gas flow to the processing area, reduce the energy consumption of electrolytic bubbles, and improve the discharge energy to achieve efficient ECDM processing. Experimental results indicate that compared with a solid electrode, the porous electrode has faster electrolyte renewal, smaller bubble volume, more-stable voltage characteristics, 22.55% less overcut, a 4.7% smaller heat-affected zone, and better deep hole processing ability. Experimental results for p-ECDM assisted by controlled airflow demonstrate a 54.23% increase in the material removal rate.

The rise of electrochemical surface science: From in situ interface structure to operando dynamics

Surface science studies of electrochemical interfaces and processes have gained increasing popularity in the last decades, owning to the increasing importance of electrochemistry for key technologies of the 21th century, especially in electric energy storage and conversion. In situ and operando surface-sensitive methods, such as scanning probe microscopy and surface X-ray diffraction, as well as complementary ab initio theory can provide atomic-scale information on solid electrode surface in contact with liquid electrolytes, including structural changes under reaction conditions. The level of detail obtainable by these approaches is illustrated in this short review for selected examples. These include the adsorption of sulfate and other oxyanions, where a crucial role of coadsorbed water is found, the restructuring of Cu electrode surfaces under hydrogen evolution and CO2 reduction conditions, and the mechanisms of electrochemical Pt oxidation and its correlation with Pt dissolution.