Room-Temperature Deposition of δ-NiGa Thin Films and Nanoparticles via Magnetron Sputtering.

Magnetron sputtering is a versatile method for investigating model system catalysts thanks to its simplicity, reproducibility, and chemical-free synthesis process. It has recently emerged as a promising technique for synthesizing δ-NiGa thin films. Physically deposited thin films have significant potential to clarify certain aspects of catalysts by eliminating parameters such as particle size dependence, metal-support interactions, and the presence of surface ligands.

Magnetron Sputtering of Pure δ-NiGa Thin Films for CO Hydrogenation.

Previous studies have identified δ-NiGa as a promising catalyst for the hydrogenation of CO to methanol at atmospheric pressure. Given its recent discovery, the current understanding of this catalyst is very limited. Additionally, the presence of multiple thermodynamically stable crystal phases in the Ni/Ga system complicates the experiments and their interpretation.

An experimental perspective on nanoparticle electrochemistry.

While model studies with small nanoparticles offer a bridge between applied experiments and theoretical calculations, the intricacies of working with well-defined nanoparticles in electrochemistry pose challenges for experimental researchers. This perspective dives into nanoparticle electrochemistry, provides experimental insights to uncover their intrinsic catalytic activity and draws conclusions about the effects of altering their size, composition, or loading. Our goal is to help uncover unexpected contamination sources and establish a robust experimental methodology, which eliminates external parameters that can overshadow the intrinsic activity of the nanoparticles.

Spin-mediated promotion of Co catalysts for ammonia synthesis.

Over the past two decades, there has been growing interest in developing catalysts to enable Haber-Bosch ammonia synthesis under milder conditions than currently pertain. Rational catalyst design requires theoretical guidance and clear mechanistic understanding. Recently, a spin-mediated promotion mechanism was proposed to activate traditionally unreactive magnetic materials such as cobalt (Co) for ammonia synthesis by introducing hetero metal atoms bound to the active site of the catalyst surface.

Long-term continuous ammonia electrosynthesis.

Ammonia is crucial as a fertilizer and in the chemical industry and is considered to be a carbon-free fuel. Ammonia electrosynthesis from nitrogen under ambient conditions offers an attractive alternative to the Haber-Bosch process, and lithium-mediated nitrogen reduction represents a promising approach to continuous-flow ammonia electrosynthesis, coupling nitrogen reduction with hydrogen oxidation. However, tetrahydrofuran, which is commonly used as a solvent, impedes long-term ammonia production owing to polymerization and volatility problems.

Phenol as proton shuttle and buffer for lithium-mediated ammonia electrosynthesis.

Ammonia is a crucial component in the production of fertilizers and various nitrogen-based compounds. Now, the lithium-mediated nitrogen reduction reaction (Li-NRR) has emerged as a promising approach for ammonia synthesis at ambient conditions. The proton shuttle plays a critical role in the proton transfer process during Li-NRR.

Stable mass-selected AuTiO nanoparticles for CO oxidation.

Stability under reactive conditions poses a common challenge for cluster- and nanoparticle-based catalysts. Since the catalytic properties of <5 nm gold nanoparticles were first uncovered, optimizing their stability at elevated temperatures for CO oxidation has been a central theme. Here we report direct observations of improved stability of AuTiO alloy nanoparticles for CO oxidation compared with pure Au nanoparticles on TiO.

Tailoring the facet distribution on copper with chloride.

Electrocatalytic reactions are sensitive to the catalyst surface structure. Therefore, finding methods to determine active surface sites with different geometry is essential to address the structure-electrocatalytic performance relationships. In this work, we propose a simple methodology to tune and quantify the surface structure on copper catalysts.

Unraveling the rate-determining step of C products during electrochemical CO reduction.

The electrochemical reduction of CO has drawn a large amount of attention due to its potential to produce sustainable fuels and chemicals by using renewable energy. However, the reaction's mechanism is not yet well understood. A major debate is whether the rate-determining step for the generation of multi-carbon products is C-C coupling or CO hydrogenation.

Gold Nanoparticles for CO Electroreduction: An Optimum Defined by Size and Shape.

Understanding the size-dependent behavior of nanoparticles is crucial for optimizing catalytic performance. We investigate the differences in selectivity of size-selected gold nanoparticles for CO electroreduction with sizes ranging from 1.5 to 6.

Calcium-mediated nitrogen reduction for electrochemical ammonia synthesis.

Ammonia (NH) is a key commodity chemical for the agricultural, textile and pharmaceutical industries, but its production via the Haber-Bosch process is carbon-intensive and centralized. Alternatively, an electrochemical method could enable decentralized, ambient NH production that can be paired with renewable energy. The first verified electrochemical method for NH synthesis was a process mediated by lithium (Li) in organic electrolytes.

Impact of Anodic Oxidation Reactions in the Performance Evaluation of High-Rate CO /CO Electrolysis.

The membrane-electrode assembly (MEA) approach appears to be the most promising technique to realize the high-rate CO /CO electrolysis, however there are major challenges related to the crossover of ions and liquid products from cathode to anode via the membrane and the concomitant anodic oxidation reactions (AORs). In this perspective, by combining experimental and theoretical analyses, several impacts of anodic oxidation of liquid products in terms of performance evaluation are investigated. First, the crossover behavior of several typical liquid products through an anion-exchange membrane is analyzed.

Retrofittable plug-flow reactor for in situ high-temperature vibrating sample magnetometry with well-controlled gas atmospheres.

We have developed an in situ sample-holder-akin to a quartz-based plug-flow reactor-for vibrating sample magnetometry (VSM) in gas-controlled environments at ambient pressure and temperatures up to ∼1000 °C. The holder matches onto a specific type of vibrating sample magnetometer (Lake Shore model 7404-S), but the principles are applicable to other types of VSM. The holder has been tested on powder samples of Co particles on a MgAl2O4 support in both reducing and oxidizing atmospheres.

Is Ethanol Essential for the Lithium-Mediated Nitrogen Reduction Reaction?

The lithium-mediated nitrogen reduction reaction (Li-NRR) is a promising method for decentralized ammonia synthesis using renewable energy. An organic electrolyte is utilized to combat the competing hydrogen evolution reaction, and lithium is plated to activate the inert N molecule. Ethanol is commonly used as a proton shuttle to provide hydrogen to the activated nitrogen.

A re-useable microreactor for dynamic and sensitive photocatalytic measurements: Exemplified by the photoconversion of ethanol on Pt-loaded titania P25.

Despite numerous advancements in synthesizing photoactive materials, the evaluation of their catalytic performance remains challenging since their fabrication often involves tedious strategies, yielding only low quantities in the μ-gram scale. In addition, these model catalysts exhibit different forms, such as powders or film(-like) structures grown on various supporting materials. Herein, we present a versatile gas phase μ-photoreactor, compatible with different catalyst morphologies, which is, in contrast to existing systems, re-openable and -useable, allowing not only post-characterization of the photocatalytic material but also enabling catalyst screening studies in short experimental time intervals.

Catalyst Stability Considerations for Electrochemical Energy Conversion with Non-Noble Metals: Do We Measure on What We Synthesized?

Working with non-noble electrocatalysts poses significant experimental challenges to unambiguously evaluate their intrinsic activity and characterize their working state and possible structural and compositional changes before, during, and after activity testing. Despite the vast number of studies on non-noble catalysts, these issues are still not addressed sufficiently-hindering significant progress in the field. In this Perspective, we present pitfalls and challenges when working with non-noble-metal-based electrocatalysts from catalyst synthesis, over electrochemical testing, to post-reaction characterization, and suggest potential solutions to overcome these difficulties.

Enriching Surface-Accessible CO in the Zero-Gap Anion-Exchange-Membrane-Based CO Electrolyzer.

Zero-gap anion exchange membrane (AEM)-based CO electrolysis is a promising technology for CO production, however, their performance at elevated current densities still suffers from the low local CO concentration due to heavy CO neutralization. Herein, via modulating the CO feed mode and quantitative analyzing CO utilization with the aid of mass transport modeling, we develop a descriptor denoted as the surface-accessible CO concentration ([CO ] ), which enables us to indicate the transient state of the local [CO ]/[OH ] ratio and helps define the limits of CO -to-CO conversion. To enrich the [CO ] , we developed three general strategies: (1) increasing catalyst layer thickness, (2) elevating CO pressure, and (3) applying a pulsed electrochemical (PE) method.

Electrosynthesis of ammonia with high selectivity and high rates via engineering of the solid-electrolyte interphase.

Ammonia is a large-scale commodity essential to fertilizer production, but the Haber-Bosch process leads to massive emissions of carbon dioxide. Electrochemical ammonia synthesis is an attractive alternative pathway, but the process is still limited by low ammonia production rate and faradaic efficiency. Herein, guided by our theoretical model, we present a highly efficient lithium-mediated process enabled by using different lithium salts, leading to the formation of a uniform solid-electrolyte interphase (SEI) layer on a porous copper electrode.

The low overpotential regime of acidic water oxidation part I: the importance of O detection.

The high overpotential required for the oxygen evolution reaction (OER) represents a significant barrier for the production of closed-cycle renewable fuels and chemicals. Ruthenium dioxide is among the most active catalysts for OER in acid, but the activity at low overpotentials can be difficult to measure due to high capacitance. In this work, we use electrochemistry - mass spectrometry to obtain accurate OER activity measurements spanning six orders of magnitude on a model series of ruthenium-based catalysts in acidic electrolyte, quantifying electrocatalytic O production at potential as low as 1.

The low overpotential regime of acidic water oxidation part II: trends in metal and oxygen stability numbers.

The operating conditions of low pH and high potential at the anodes of polymer electrolyte membrane electrolysers restrict the choice of catalysts for the oxygen evolution reaction (OER) to oxides based on the rare metals iridium or ruthenium. In this work, we investigate the stability of both the metal atoms and, by quantitative and highly sensitive O isotope labelling experiments, the oxygen atoms in a series of RuO and IrO electrocatalysts during the OER in the mechanistically interesting low overpotential regime. We show that materials based on RuO have a higher dissolution rate than the rate of incorporation of labelled oxygen from the catalyst into the O evolved ("labelled OER"), while for IrO -based catalysts the two rates are comparable.

Oxygen-Enhanced Chemical Stability of Lithium-Mediated Electrochemical Ammonia Synthesis.

Although oxygen added to nonaqueous lithium-mediated electrochemical ammonia synthesis (LiMEAS) enhances Faradaic efficiency, its effect on chemical stability and byproducts requires understanding. Therefore, standardized high-resolution gas chromatography-mass spectrometry and nuclear magnetic resonance were employed. Different volatile degradation products have been qualitatively analyzed and quantified in tetrahydrofuran electrolyte by adding some oxygen to LiMEAS.