Stability of Bimetallic PtRu - From Model Surfaces to Nanoparticulate Electrocatalysts.

Fundamental research campaigns in electrocatalysis often involve the use of model systems, such as single crystals or magnetron-sputtered thin films (single metals or metal alloys). The downsides of these approaches are that oftentimes only a limited number of compositions are picked and tested (guided by chemical intuition) and that the validity of trends is not verified under operating conditions typically present in real devices. These together can lead to deficient conclusions, hampering the direct application of newly discovered systems in real devices.

Stable Operation of Paired CO Reduction/Glycerol Oxidation at High Current Density.

Despite the considerable efforts made by the community, the high operation cell voltage of CO electrolyzers is still to be decreased to move toward commercialization. This is mostly due to the high energy need of the oxygen evolution reaction (OER), which is the most often used anodic pair for CO reduction. In this study, OER was replaced by the electrocatalytic oxidation of glycerol using carbon-supported Pt nanoparticles as an anode catalyst.

One-step electrodeposition of binder-containing Cu nanocube catalyst layers for carbon dioxide reduction.

To reach industrially relevant current densities in the electrochemical reduction of carbon dioxide, this process must be performed in continuous-flow electrolyzer cells, applying gas diffusion electrodes. Beyond the chemical composition of the catalyst, both its morphology and the overall structure of the catalyst layer are decisive in terms of reaction rate and product selectivity. We present an electrodeposition method for preparing coherent copper nanocube catalyst layers on hydrophobic carbon paper, hence forming gas diffusion electrodes with high coverage in a single step.

Stability of high-entropy alloys under electrocatalytic conditions.

High-entropy alloys are claimed to possess superior stability due to thermodynamic contributions. However, this statement mostly lies on a hypothetical basis. In this study, we use on-line inductively coupled plasma mass spectrometer to investigate the dissolution of five representative electrocatalysts in acidic and alkaline media and a wide potential window targeting the most important applications.

Local hydrophobicity allows high-performance electrochemical carbon monoxide reduction to C products.

While CO can already be produced at industrially relevant current densities CO electrolysis, the selective formation of C products seems challenging. CO electrolysis, in principle, can overcome this barrier, hence forming valuable chemicals from CO in two steps. Here we demonstrate that a mass-produced, commercially available polymeric pore sealer can be used as a catalyst binder, ensuring high rate and selective CO reduction.

Electrolyte Engineering Stabilizes Photoanodes Decorated with Molecular Catalysts.

Invited for this month's cover is the group of Dunwei Wang from Boston College and Serhiy Cherevko from the Helmholtz Institute Erlangen-Nürnberg for Renewable Energy. The image illustrates the impact of different electrolyte environments on the stability of hematite decorated with an iridium molecular catalyst used for solar water splitting. The Research Article itself is available at 10.

Electrolyte Engineering Stabilizes Photoanodes Decorated with Molecular Catalysts.

Molecular catalysts are promising oxygen evolution promoters in conjunction with photoanodes for solar water splitting. Maintaining the stability of both photoabsorber and cocatalyst is still a prime challenge, with many efforts tackling this issue through sophisticated material designs. Such approaches often mask the importance of the electrode-electrolyte interface and overlook easily tunable system parameters, such as the electrolyte environment, to improve efficiency.

High-throughput exploration of activity and stability for identifying photoelectrochemical water splitting materials.

The experimental high-throughput (HT) exploration for a suitable solar water splitting photoanode has greatly relied on photoactivity as the sole descriptor to identify a promising region within the searched composition space. Although activity is essential, it is not sufficient for describing the overall performance and excludes other pertinent criteria for photoelectrochemical (PEC) water splitting. Photostability in the form of (photo)electrocatalyst dissolution must be tracked to illustrate the intricate relation between activity and stability for multinary photoelectrocatalysts.

Atomistic Insights into Activation and Degradation of LaSrCoO Electrocatalysts under Oxygen Evolution Conditions.

The stability of perovskite oxide catalysts for the oxygen evolution reaction (OER) plays a critical role in their applicability in water splitting concepts. Decomposition of perovskite oxides under applied potential is typically linked to cation leaching and amorphization of the material. However, structural changes and phase transformations at the catalyst surface were also shown to govern the activity of several perovskite electrocatalysts under applied potential.

On the electrocatalytical oxygen reduction reaction activity and stability of quaternary RhMo-doped PtNi/C octahedral nanocrystals.

Recently proposed bimetallic octahedral Pt-Ni electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC) cathodes suffer from particle instabilities in the form of Ni corrosion and shape degradation. Advanced trimetallic Pt-based electrocatalysts have contributed to their catalytic performance and stability. In this work, we propose and analyse a novel quaternary octahedral (oh-)Pt nanoalloy concept with two distinct metals serving as stabilizing surface dopants.

Intermittent Operation of CO Electrolyzers at Industrially Relevant Current Densities.

We demonstrate the dynamic operation of CO electrolyzer cells, with a power input mimicking the output of a solar photovoltaic power plant. The zero-gap design ensured efficient intermittent operation for a week, while avoiding significant performance loss.

Anode Catalysts in CO Electrolysis: Challenges and Untapped Opportunities.

The field of electrochemical carbon dioxide reduction has developed rapidly during recent years. At the same time, the role of the anodic half-reaction has received considerably less attention. In this Perspective, we scrutinize the reports on the best-performing CO electrolyzer cells from the past 5 years, to shed light on the role of the anodic oxygen evolution catalyst.

Local Chemical Environment Governs Anode Processes in CO Electrolyzers.

A major goal within the CO electrolysis community is to replace the generally used Ir anode catalyst with a more abundant material, which is stable and active for water oxidation under process conditions. Ni is widely applied in alkaline water electrolysis, and it has been considered as a potential anode catalyst in CO electrolysis. Here we compare the operation of electrolyzer cells with Ir and Ni anodes and demonstrate that, while Ir is stable under process conditions, the degradation of Ni leads to a rapid cell failure.

Performance of Quaternized Polybenzimidazole-Cross-Linked Poly(vinylbenzyl chloride) Membranes in HT-PEMFCs.

High-temperature proton-exchange membrane fuel cells (HT-PEMFCs) are mostly based on acid-doped membranes composed of polybenzimidazole (PBI). A severe drawback of acid-doped membranes is the deterioration of mechanical properties upon increasing acid-doping levels. Cross-linking of different polymers is a way to mitigate stability issues.

Accessing In Situ Photocorrosion under Realistic Light Conditions: Photoelectrochemical Scanning Flow Cell Coupled to Online ICP-MS.

High-impact photoelectrode materials for photoelectrochemical (PEC) water splitting are distinguished by synergistically attaining high photoactivity and stability at the same time. With numerous efforts toward optimizing the activity, the bigger challenge of tailoring the durability of photoelectrodes to meet industrially relevant levels remains. In situ photostability measurements hold great promise in understanding stability-related properties.

Photocorrosion of WO Photoanodes in Different Electrolytes.

Photocorrosion of an n-type semiconductor is anticipated to be unfavorable if its decomposition potential is situated below its valence band-edge position. Tungsten trioxide (WO) is generally considered as a stable photoanode for different photoelectrochemical (PEC) applications. Such oversimplified considerations ignore reactions with electrolytes added to the solvent.

Hybrid FeNiOOH/α-FeO/Graphene Photoelectrodes with Advanced Water Oxidation Performance.

In this study, the photoelectrochemical behavior of electrodeposited FeNiOOH/FeO/graphene nanohybrid electrodes is investigated, which has precisely controlled structure and composition. The photoelectrode assembly is designed in a bioinspired manner where each component has its own function: FeO is responsible for the absorption of light, the graphene framework for proper charge carrier transport, while the FeNiOOH overlayer for facile water oxidation. The effect of each component on the photoelectrochemical behavior is studied by linear sweep photovoltammetry, incident photon-to-charge carrier conversion efficiency measurements, and long-term photoelectrolysis.

Electrodeposition of Silver Vanadate Films: A Tale of Two Polymorphs.

Two polymorphs of AgVO , namely the α- and β- forms, were prepared and their physical, structural, optical, electrochemical, and photoelectrochemical characteristics were compared using a battery of experimental and theoretical tools. A two-step method, previously developed in the our laboratory for the electrodeposition of inorganic semiconductor films, was applied to the electrosynthesis of silver vanadate (AgVO ) films on transparent, conducting oxide surfaces. In the first step, silver was cathodically deposited from a non-aqueous bath containing silver nitrate.

Role of f Electrons in the Optical and Photoelectrochemical Behavior of Ca(LaCe )S (0 ≤ x ≤ 1).

This study focuses on a solid solution series, Ca(LaCe )S (0 ≤ x ≤ 1), where the f electron density is absent in CaLaS and is progressively increased until it is maximized in CaCeS. Correspondingly, these samples, synthesized by a sealed ampule method, showed progressive variations in color ranging from gray for CaLaS to orange-red for CaCeS. The crystal structural nuances of both the end members and three solid solutions with x = 0.

Photoelectrochemical Behavior of PEDOT/Nanocarbon Electrodes: Fundamentals and Structure-Property Relationships.

In this study, we investigated the photoelectrochemical behavior of poly(3,4-ethylenedioxythiophene) (PEDOT)/carbon nanotube (CNT) and PEDOT/graphene nanocomposite photoelectrodes for the first time. Electrodeposition allowed control of both the composition and the morphology (as demonstrated by both transmission and scanning electron microscopy images) and also ensured an intimate contact between the PEDOT film and the nanocarbon scaffold. The effect of CNT and graphene on the photoelectrochemical behavior of the nanocomposite samples was studied by linear sweep photovoltammetry, incident photon-to-charge-carrier conversion efficiency measurements, and long-term photoelectrolysis coupled with gas-chromatographic product analysis.

Polyaniline films photoelectrochemically reduce CO2 to alcohols.

In this communication, we demonstrate that polyaniline, the very first example of an organic semiconductor, is a promising photocathode material for the conversion of carbon dioxide (CO2) to alcohol fuels. CO2 is a greenhouse gas; thus using solar energy to convert CO2 to transportation fuels (such as methanol or ethanol) is a value-added approach to simultaneous generation of alternative fuels and environmental remediation of carbon emissions. Insights into its unique behavior obtained from photoelectrochemical measurements and adsorption studies, together with spectroscopic data, are presented.

Flavin Derivatives with Tailored Redox Properties: Synthesis, Characterization, and Electrochemical Behavior.

This study establishes structure-property relationships for four synthetic flavin molecules as bioinspired redox mediators in electro- and photocatalysis applications. The studied flavin compounds were disubstituted with polar substituents at the N1 and N3 positions (alloxazine) or at the N3 and N10 positions (isoalloxazines). The electrochemical behavior of one such synthetic flavin analogue was examined in detail in aqueous solutions of varying pH in the range from 1 to 10.

Controlled Photocatalytic Synthesis of Core-Shell SiC/Polyaniline Hybrid Nanostructures.

Hybrid materials of electrically conducting polymers and inorganic semiconductors form an exciting class of functional materials. To fully exploit the potential synergies of the hybrid formation, however, sophisticated synthetic methods are required that allow for the fine-tuning of the nanoscale structure of the organic/inorganic interface. Here we present the photocatalytic deposition of a conducting polymer (polyaniline) on the surface of silicon carbide (SiC) nanoparticles.