Mechanistic Insights and Technical Challenges in Sulfur-Based Batteries: A Comprehensive / Monitoring Toolbox.

Batteries based on sulfur cathodes offer a promising energy storage solution due to their potential for high performance, cost-effectiveness, and sustainability. However, commercial viability is challenged by issues such as polysulfide migration, volume changes, uneven phase nucleation, limited ion transport, and sluggish sulfur redox kinetics. Addressing these challenges requires insights into the structural, morphological, and chemical evolution of phases, the associated volume changes and internal stresses, and ion and polysulfide diffusion within the battery.

Soft X-ray Induced Radiation Damage in Dip-and-Pull Photon Absorption and Photoelectron Emission Experiments.

X-ray irradiation can induce chemical reactions on surfaces. In X-ray spectroscopic experiments, such reactions may result in spectrum distortion and are termed radiation damage. In this study, we investigate the X-ray-induced chemical reaction at the partially oxidized copper surface in the settings of the dip-and-pull experiment, a method that generates liquid-solid interfaces for in situ X-ray photoelectron spectroscopy (XPS) studies.

On the Operando Structure of Ruthenium Oxides during the Oxygen Evolution Reaction in Acidic Media.

In the search for rational design strategies for oxygen evolution reaction (OER) catalysts, linking the catalyst structure to activity and stability is key. However, highly active catalysts such as IrO and RuO undergo structural changes under OER conditions, and hence, structure-activity-stability relationships need to take into account the operando structure of the catalyst. Under the highly anodic conditions of the oxygen evolution reaction (OER), electrocatalysts are often converted into an active form.

Interfacial Chemistry in the Electrocatalytic Hydrogenation of CO over C-Supported Cu-Based Systems.

Operando soft and hard X-ray spectroscopic techniques were used in combination with plane-wave density functional theory (DFT) simulations to rationalize the enhanced activities of Zn-containing Cu nanostructured electrocatalysts in the electrocatalytic CO hydrogenation reaction. We show that at a potential for CO hydrogenation, Zn is alloyed with Cu in the bulk of the nanoparticles with no metallic Zn segregated; at the interface, low reducible Cu(I)-O species are consumed. Additional spectroscopic features are observed, which are identified as various surface Cu(I) ligated species; these respond to the potential, revealing characteristic interfacial dynamics.

Dynamics over a Cu-graphite electrode during the gas-phase CO reduction investigated by APXPS.

The electrocatalytic conversion of CO to fuels and chemicals using renewable energy is a key decarbonization technology. From a technological viewpoint, the realization of such process in the gas phase and at room temperature is considered advantageous as it allows one to circumvent the limited CO solubility in liquid electrolytes and CO transport across the electrical double layer. Yet, electrocatalysts' performances reported so far are promising but not satisfactory.

Surface Electron-Hole Rich Species Active in the Electrocatalytic Water Oxidation.

Iridium and ruthenium and their oxides/hydroxides are the best candidates for the oxygen evolution reaction under harsh acidic conditions owing to the low overpotentials observed for Ru- and Ir-based anodes and the high corrosion resistance of Ir-oxides. Herein, by means of cutting edge surface and bulk sensitive X-ray spectroscopy techniques, specifically designed electrode nanofabrication and DFT calculations, we were able to reveal the electronic structure of the active IrO centers (i.e.

AgCu Bimetallic Electrocatalysts for the Reduction of Biomass-Derived Compounds.

The electrochemical transformation of biomass-derived compounds (e.g., aldehyde electroreduction to alcohols) is gaining increasing interest due to the sustainability of this process that can be exploited to produce value-added products from biowastes and renewable electricity.

The Electrophilicity of Surface Carbon Species in the Redox Reactions of CuO-CeO Catalysts.

Electronic metal-support interactions (EMSI) describe the electron flow between metal sites and a metal oxide support. It is generally used to follow the mechanism of redox reactions. In this study of CuO-CeO redox, an additional flow of electrons from metallic Cu to surface carbon species is observed via a combination of operando X-ray absorption spectroscopy, synchrotron X-ray powder diffraction, near ambient pressure near edge X-ray absorption fine structure spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy.

On the Activity/Selectivity and Phase Stability of Thermally Grown Copper Oxides during the Electrocatalytic Reduction of CO.

Revealing the active nature of oxide-derived copper is of key importance to understand its remarkable catalytic performance during the cathodic CO reduction reaction (CORR) to produce valuable hydrocarbons. Using advanced spectroscopy, electron microscopy, and electrochemically active surface area characterization techniques, the electronic structure and the changes in the morphology/roughness of thermally oxidized copper thin films were revealed during CORR. For this purpose, we developed an in situ cell for X-ray spectroscopy that could be operated accurately in the presence of gases or liquids to clarify the role of the initial thermal oxide phase and its active phase during the electrocatalytic reduction of CO.

Adsorption and activation of molecular oxygen over atomic copper(I/II) site on ceria.

Supported atomic metal sites have discrete molecular orbitals. Precise control over the energies of these sites is key to achieving novel reaction pathways with superior selectivity. Here, we achieve selective oxygen (O) activation by utilising a framework of cerium (Ce) cations to reduce the energy of 3d orbitals of isolated copper (Cu) sites.

Graphene-Capped Liquid Thin Films for Electrochemical Operando X-ray Spectroscopy and Scanning Electron Microscopy.

Electrochemistry is a promising building block for the global transition to a sustainable energy market. Particularly the electroreduction of CO and the electrolysis of water might be strategic elements for chemical energy conversion. The reactions of interest are inner-sphere reactions, which occur on the surface of the electrode, and the biased interface between the electrode surface and the electrolyte is of central importance to the reactivity of an electrode.

Revealing the Active Phase of Copper during the Electroreduction of CO in Aqueous Electrolyte by Correlating X-ray Spectroscopy and Electron Microscopy.

The variation in the morphology and electronic structure of copper during the electroreduction of CO into valuable hydrocarbons and alcohols was revealed by combining surface- and bulk-sensitive X-ray spectroscopies with electrochemical scanning electron microscopy. These experiments proved that the electrified interface surface and near-surface are dominated by reduced copper. The selectivity to the formation of the key C-C bond is enhanced at higher cathodic potentials as a consequence of increased copper metallicity.

Controlling the Oxidation State of the Cu Electrode and Reaction Intermediates for Electrochemical CO Reduction to Ethylene.

Understanding the role of the oxidation state of the Cu surface and surface-adsorbed intermediate species in electrochemical CO reduction is crucial for the development of selective CO-to-fuel electrocatalysts. In this study, the electrochemical CO reduction mechanism over the Cu catalysts with various oxidation states was studied by using in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), in situ soft X-ray absorption spectroscopy (Cu L-edge), and online gas chromatography measurements. The atop-adsorbed CO (CO) intermediate is obtained on the electrodeposited Cu surface which primarily has the oxidation state of Cu(I).

The Oxidation of Platinum under Wet Conditions Observed by Electrochemical X-ray Photoelectron Spectroscopy.

During the electrochemical reduction of oxygen, platinum catalysts are often (partially) oxidized. While these platinum oxides are thought to play a crucial role in fuel cell degradation, their nature remains unclear. Here, we studied the electrochemical oxidation of Pt nanoparticles using in situ XPS.

Operando spectroscopy study of the carbon dioxide electro-reduction by iron species on nitrogen-doped carbon.

The carbon-carbon coupling via electrochemical reduction of carbon dioxide represents the biggest challenge for using this route as platform for chemicals synthesis. Here we show that nanostructured iron (III) oxyhydroxide on nitrogen-doped carbon enables high Faraday efficiency (97.4%) and selectivity to acetic acid (61%) at very-low potential (-0.

The Role of Adsorbed and Subsurface Carbon Species for the Selective Alkyne Hydrogenation Over a Pd-Black Catalyst: An Study of Bulk and Surface.

The selective hydrogenation of propyne over a Pd-black model catalyst was investigated under conditions at 1 bar making use of advanced X-ray diffraction (bulk sensitive) and photo-electron spectroscopy (surface sensitive) techniques. It was found that the population of subsurface species controls the selective catalytic semi-hydrogenation of propyne to propylene due to the formation of surface and near-surface PdC that inhibits the participation of more reactive bulk hydrogen in the hydrogenation reaction. However, increasing the partial pressure of hydrogen reduces the population of PdC with the concomitant formation of a β-PdH phase up to the surface, which is accompanied by a lattice expansion, allowing the participation of more active bulk hydrogen which is responsible for the unselective total alkyne hydrogenation.

The Electro-Deposition/Dissolution of CuSO Aqueous Electrolyte Investigated by In Situ Soft X-ray Absorption Spectroscopy.

The electrodeposition nature of copper on a gold electrode in a 4.8 pH CuSO solution was inquired using X-ray absorption spectroscopy, electrochemical quartz crystal microbalance, and thermal desorption spectroscopy techniques. Our results point out that the electrodeposition of copper prompts the formation of stable oxi-hydroxide species with a formal oxidation state Cu without the evidence of metallic copper formation (Cu).

Bulk-Sensitive Detection of the Total Ion Yield for X-ray Absorption Spectroscopy in Liquid Cells.

Detection of ionic current with two electrodes installed in a liquid cell has been established previously as an effective method, termed as total ion yield (TIY), to acquire X-ray absorption (XA) spectra of liquid solutions behind a membrane. In this study, the exact locations where TIY signals are generated are further investigated and unequivocally identified. The detected ionic current stems dominantly from the bulk solution species while only marginally from the species located at the membrane-solution interface.

observation of reactive oxygen species forming on oxygen-evolving iridium surfaces.

Water splitting performed in acidic media relies on the exceptional performance of iridium-based materials to catalyze the oxygen evolution reaction (OER). In the present work, we use X-ray photoemission and absorption spectroscopy to resolve the long-standing debate about surface species present in iridium-based catalysts during the OER. We find that the surface of an initially metallic iridium model electrode converts into a mixed-valent, conductive iridium oxide matrix during the OER, which contains O and electrophilic O species.