As a promising chemical storage medium for hydrogen, the thermal decomposition of ammonia using non-precious metal catalysts, such as Co, Ni, and Fe, has recently gained significant attention. In our work, we are exploring new avenues for the synthesis of such catalysts. We prepare nanostructured oxide precursors that contain both the active element and potential promoters in their crystal...
In the pursuit of carbon neutrality, the catalytic hydrogenation of CO₂ using renewable H₂ is considered a promising route for the production of fuels and chemicals, while its integration with carbon capture and utilization processes (ICCU) provides an alternative and innovative approach for the synthesis of value-added products.¹ Even though the formation of C₁ molecules by CO/CO₂...
CO2 hydrogenation is a kinetically limited reaction, occurring exclusively at the catalyst surface. To achieve satisfactory catalytic conversions, it is essential to form a reactive interface that facilitates the adsorption of CO2 and its subsequent conversion to the desired products, i.e., methanol. The industrially established system for methanol production via CO2 hydrogenation is Cu/ZnO,...
CO2 reduction should minimize hydrogen use while co-producing base chemicals. Plasma pyrolysis generates black carbon along with ethylene and acetylene1. Due to operational hazards, concentrated acetylene must be selectively hydrogenated into valuable ethylene. Pd-based catalysts are commonly used for this reaction. However, the surface and subsurface dynamics of active...
Abstract
Ammonia is industrially produced by the Haber-Bosch process over a fused, multi-promoted iron-based catalyst [1]. Current knowledge about this reaction has been derived from model systems with less structural complexity impeding a clear-cut structure-activity correlation [1,2]. Here, we explore the real structure and its structural evolution of complex, technical,...
Solid oxide cells (SOCs) are highly efficient electrochemical devices that convert electrical energy into chemical fuels, offering a versatile solution for energy storage to mitigate the intermittency of renewable energy sources in modern power systems. Operating at elevated temperatures, typically above 600 °C, SOCs benefit from favorable thermodynamic and kinetic efficiencies. However, these...
In recent years, nickel-oxyhydroxide has come into focus as a low-cost and efficient material in the Oxygen Evolution Reaction (OER) via electrochemical water splitting. It is a prototypical active and stable catalyst for alkaline OER, however, its precise reaction mechanism is not yet fully understood. We coupled pulse voltammetry, operando X-ray absorption spectroscopy (XAS) and density...
Cobalt-based oxides are excellent catalysts for oxidation reactions, both in thermal catalysis1 and in electrocatalysis.2 Here, we present an overview of combined operando X-ray spectroscopic and operando transmission electron microscopic studies of cobalt spinel oxides (Co3O4) and perovksites (LaCoxFe1-xO3) in...
CO₂ electrocatalytic reduction reaction allows to convert environmentally harmful CO₂ into useful chemicals. To this aim, Cu stands out as the only catalyst capable of producing valuable hydrocarbons and alcohols, such as ethylene and ethanol.1-2
The catalyst surface structure plays a key role in determining the selectivity towards certain carbon products; in particular, vicinal...
The electrocatalytic reduction of nitrate (NO3RR) presents a promising approach for decentralized clean ammonia (NH3) production, while simultaneously mitigating environmental pollution caused by toxic and carcinogenic nitrate-laden wastewater.[1] Copper-based materials are attractive NO3RR catalysts due to their affordability and high NH3 selectivity.[2] However, the mismatch in adsorption...
Electrocatalytic water splitting is one of the most promising technologies for producing green hydrogen from renewable resources. However, the anodic oxygen evolution reaction (OER) remains the bottleneck of this process due to its sluggish kinetics. In alkaline water electrolysis, nanocrystalline spinel-type Co3O4 is a highly attractive anode material due to its low...
This study explores the epitaxial growth of cobalt oxide (Co₃O₄) thin films on platinum (Pt(100)) single crystals, focusing on the interfacial phenomena that drive the Oxygen Evolution Reaction (OER) in electrochemical water-splitting.1 By systematically varying film thickness, we uncover the delicate interplay between interfacial charge transfer and surface polarization, both...
Various electrocatalytic reactions are influenced by cationic species in the electrolyte, although their exact role is often debated.1 Resolving the electrochemical interface is thus essential for comprehending the interaction of electrolyte species with electrode surfaces and designing improved catalytic systems. Surface X-ray Diffraction (SXRD) has been shown to be a powerful technique for...
The hydrogen evolution reaction (HER) is the most prominent electrocatalytic reaction. It is needed to generate green hydrogen from water and simultaneously serves as the test reaction for general electrocatalyst function in aqueous media. Despite this, it remains poorly understood. Attempts have been made to describe HER kinetics according to Brønsted-Evans-Polanyi relationships for which the...
The oxygen reduction reaction (ORR) is a key reaction in fuel cells and Li-air batteries. Despite this, the fundamental reaction mechanism is still not understood. Frequently, kinetics are described with Butler-Volmer type theory, assuming that the electric bias is completely translated in reducing the activation enthalpy (activation energy). However, at solid-electrolyte interfaces, the bias...
Electrocatalysts exist within a complex liquid reaction environment and experience (electro)chemical driving force that can change their structural and composition from the as-synthesized state. It is, therefore, crucial that we have insight into the working state of the catalyst if we are to reliably relate the catalyst morphologies with this associated catalytic performance. Even though this...
One of the most important aspects of rational catalyst design is controlling the environment of active sites. In electrocatalysis, the use of organic ligands has emerged as a promising strategy to tune the activity and selectivity of the catalyst. In particular, Arduengo-type N-heterocyclic carbenes (NHCs) and the closely related N-heterocyclic olefins (NHO) have emerged as promising ligands...
Carbon capture and reutilization is a necessity for transitioning towards a sustainable society. Electrocatalytic carbon dioxide reduction reactions (CO2RR) to hydrocarbons at copper cathodes is one promising route, where the selectivity and activity are dictated by a complex interplay of copper oxidation state, structure, and oxygen content at the (sub)surface.[1] Stabilization of these...
Transition metal-nitrogen-doped carbons (TM-N-C) are promising catalysts for several important electrochemical processes, including CO$_{2}$ electrocatalytic reduction (CO$_{2}$RR) [1]. In these catalysts, nitrogen is incorporated into a carbon matrix, creating binding sites for metal species. The latter are believed to be the active sites for CO$_{2}$RR. Among different TM-N-Cs, Ni-N-C is...
Catalysts evolve dynamically under operating conditions. From atomic-scale restructuring to severe coke formation, the dynamic evolution of the catalyst structure is closely linked to changes in catalytic performance. Operando X-ray absorption spectroscopy (XAS) is a well-suited technique to probe the dynamic structural changes under realistic reaction conditions and to correlate rich...
The implementation of single atom catalysts (SACs) critically depends on the stability of single atoms towards sintering. We have recently shown that the catalyst pre-treatment with oxygen plasma improves stability and reactivity of Pt/CeO2 SACs in CO oxidation.1 Here we focused on employing “cold” plasma to SACs for reactions under the reducing (H2 containing) atmosphere. In this work, we...
The hydrogenation of CO$_2$ to methanol occurs with high efficiency on Cu/ZnO-based catalysts. However, the nature of the Cu−Zn interaction and especially the role of Zn in Cu/ZnO catalysts are still not fully understood. In the industrial Cu/ZnO/Al$_2$O$_3$ catalyst, Zn was found to migrate onto the Cu surface during the reaction, thus forming a Cu−ZnO interface that is crucial for a high...
Indium oxide (In2O3) has recently received considerable attention in the catalysis community due to its unexpectedly high selectivity in the hydrogenation of CO2 to methanol.1 Metal deposition onto In2O3 substantially promotes the activity, while the selectivity remains close to that of bare In2O3 independent of the metal used.2,3 To get insight into the metal/In2O3 interaction and the role of...
Copper (Cu) is a leading catalyst for CO$_2$ electroreduction (CO2RR) to multi-carbon products, though its structure sensitivity and stability remain debated. This study reveals that CO2RR does not occur on perfect Cu(111) and Cu(100) surfaces but rather on defect sites, such as steps and kinks [1,2]. Under reaction conditions, these planar surfaces restructure into more active stepped...
CuNi nanoparticles have been successfully employed as catalysts in many chemical reactions. Depending on reaction conditions changes in their surface composition are observed, due to the adsorption of molecules. Here, we studied the Ni/Cu(100) single crystal surface as a model system for CO2 hydrogenation to explore the segregation trends under different reaction atmospheres. Exposure to an...
Methane dry reforming (MDR, CH₄ + CO₂ → 2CO + 2H₂) is a promising pathway to produce syngas while reducing the net emission of two of the most harmful greenhouse gases. The industrially relevant catalyst, Ni, suffers from major drawbacks, such as carbon deposition and sintering at high reaction temperatures1.
One alternative to address these issues is the use of bimetallic catalysts2. The...
The structure of interfacial hydration layers plays a crucial role in energy and chemical conversion processes, impacting the kinetics of electrocatalytic reactions such as CO2 electroreduction (CO2RR) and hydrogen evolution (HER). We reveal the intricate interplay between carbon and proton sources within the microenvironment of bicarbonate electrolytes and highlight the...
