Mechanistic insight into electrocatalytic glyoxal reduction on copper and its relation to CO reduction.

Copper electrodes produce several industrially relevant chemicals and fuels during the electrochemical CO reduction reaction (CORR). Knowledge about the reaction pathways can help tune the reaction selectivity toward higher-value products. To probe the uncertain role of the C molecule glyoxal, we electrochemically reduced it on polycrystalline Cu and quantified its liquid-phase products, namely, ethanol, ethylene glycol, and acetaldehyde.

Analysing the relationship between the fields of thermo- and electrocatalysis taking hydrogen peroxide as a case study.

Catalysis is inherently driven by the interaction of reactants, intermediates and formed products with the catalyst’s surface. In order to reach the desired transition state and to overcome the kinetic barrier, elevated temperatures or electrical potentials are employed to increase the rate of reaction. Despite immense efforts in the last decades, research in thermo- and electrocatalysis has often preceded in isolation, even for similar reactions.

CO Electroreduction on Silver Foams Modified by Ionic Liquids with Different Cation Side Chain Length.

Ionic liquids (ILs) are capable of tuning the kinetics of electroreduction processes by modifying a catalyst interface. In this work, a group of hydrophobic imidazolium-based ILs were immobilized on Ag foams by using a procedure known as "solid catalyst with ionic liquid layer" (SCILL). The derived electrocatalysts demonstrated altered selectivity and CO production rates for the electrochemical reduction of CO compared to the unmodified Ag foam.

Electroreductive 5-Hydroxymethylfurfural Dimerization on Carbon Electrodes.

The electrochemical conversion of biomass-based compounds to fuels and fuel precursors can aid the defossilization of the transportation sector. Herein, the electrohydrodimerization of 5-hydroxymethylfurfural (HMF) to the fuel precursor 5,5'-bis(hydroxymethyl)hydrofuroin (BHH) was investigated on different carbon electrodes. Compared to boron-doped diamond (BDD) electrodes, on glassy carbon (GC) electrodes a less negative HMF reduction onset potential and a switch in product selectivity from BHH to the electrocatalytic hydrogenation product 2,5-di(hydroxymethyl)furan (DHMF) with increasing overpotential was found.

Implementation of an enclosed ionization interface for the analysis of liquid sample streams with direct analysis in real time mass spectrometry.

Rationale: The development of an interface to analyze liquid sample streams with direct analysis in real time mass spectrometry (DART-MS) is of great interest for coupling various analytical techniques, using non-volatile salts, with MS. Therefore, we devised an enclosed ionization interface and a sample introduction system for the versatile analysis of liquid samples with DART-MS.

Methods: The sample introduction system consists of a nebulizer, a spray chamber and a transfer line, while the confined ionization interface is created by implementing a cross-shaped housing between ion source outlet and mass spectrometer inlet.

Probing CO Reduction Pathways for Copper Catalysis Using an Ionic Liquid as a Chemical Trapping Agent.

The key to fully leveraging the potential of the electrochemical CO reduction reaction (CO2RR) to achieve a sustainable solar-power-based economy is the development of high-performance electrocatalysts. The development process relies heavily on trial and error methods due to poor mechanistic understanding of the reaction. Demonstrated here is that ionic liquids (ILs) can be employed as a chemical trapping agent to probe CO2RR mechanistic pathways.

Electrochemical Oxidation of Isopropanol on Platinum-Ruthenium Nanoparticles Studied with Real-Time Product and Dissolution Analytics.

The selective electrooxidation of 2-propanol to acetone can be used in fuel cells which, when combined with the transfer hydrogenation of acetone from liquid organic hydrogen carriers, will enable the realization of hydrogen economy without using molecular hydrogen gas for storage and transportation. We study the reaction on platinum and platinum-ruthenium nanocatalysts using unique tools for the real-time characterization of reaction and dissolution products. Acetone is the primary product on all investigated catalysts, and only traces of CO form at high potentials.

Dissolution of Platinum Single Crystals in Acidic Medium.

Platinum single crystal basal planes consisting of Pt(111), Pt(100), Pt(110) and reference polycrystalline platinum Pt(poly) were subjected to various potentiodynamic and potentiostatic electrochemical treatments in 0.1 M HClO . Using the scanning flow cell coupled to an inductively coupled plasma mass spectrometer (SFC-ICP-MS) the transient dissolution was detected on-line.

Electrochemical Real-Time Mass Spectrometry (EC-RTMS): Monitoring Electrochemical Reaction Products in Real Time.

Methods that provide real-time information are essential to resolve transients occurring at dynamic interfaces. Now a powerful method is presented that enables the time- and potential-resolved characterization of liquid and gaseous products of electrochemical reactions shortly after their formation. To demonstrate its extraordinary potential, the electrochemical real time mass spectrometry (EC-RTMS) approach is used to determine the products of the CO reduction reaction (CO RR) during potential step or sweep experiments on pristine and in situ anodized copper.

Atomically-defined model catalysts in ultrahigh vacuum and in liquid electrolytes: particle size-dependent CO adsorption on Pt nanoparticles on ordered CoO(111) films.

We have studied particle size effects on atomically-defined model catalysts both in ultrahigh vacuum (UHV) and under electrochemical (EC) conditions in liquid electrolytes. The model catalysts were prepared in UHV by physical vapour deposition (PVD) of Pt onto an ordered Co3O4(111) film on Ir(100), yielding nanoparticles (NPs) with an average size from 10 to 500 atoms per particle (0.8 to 3 nm).

Evidence for Decoupled Electron and Proton Transfer in the Electrochemical Oxidation of Ammonia on Pt(100).

The two traditional mechanisms of the electrochemical ammonia oxidation consider only concerted proton-electron transfer elementary steps and thus they predict that the rate-potential relationship is independent of the pH on the pH-corrected RHE potential scale. In this letter we show that this is not the case: the increase of the solution pH shifts the onset of the NH3-to-N2 oxidation on Pt(100) to lower potentials and also leads to higher surface concentration of formed NOad before the latter is oxidized to nitrite. Therefore, we present a new mechanism for the ammonia oxidation that incorporates a deprotonation step occurring prior to the electron transfer.

Design criteria for stable Pt/C fuel cell catalysts.

Platinum and Pt alloy nanoparticles supported on carbon are the state of the art electrocatalysts in proton exchange membrane fuel cells. To develop a better understanding on how material design can influence the degradation processes on the nanoscale, three specific Pt/C catalysts with different structural characteristics were investigated in depth: a conventional Pt/Vulcan catalyst with a particle size of 3-4 nm and two Pt@HGS catalysts with different particle size, 1-2 nm and 3-4 nm. Specifically, Pt@HGS corresponds to platinum nanoparticles incorporated and confined within the pore structure of the nanostructured carbon support, i.

Oxygen electrochemistry as a cornerstone for sustainable energy conversion.

Electrochemistry will play a vital role in creating sustainable energy solutions in the future, particularly for the conversion and storage of electrical into chemical energy in electrolysis cells, and the reverse conversion and utilization of the stored energy in galvanic cells. The common challenge in both processes is the development of-preferably abundant-nanostructured materials that can catalyze the electrochemical reactions of interest with a high rate over a sufficiently long period of time. An overall understanding of the related processes and mechanisms occurring under the operation conditions is a necessity for the rational design of materials that meet these requirements.

Influence of the electrode and the pH on the rate and the product distribution of the electrochemical removal of nitrate.

The effect of the nature of six metal electrodes (Sn, Bi, Pb, Al, Zn, In) on the rate and the distribution of the products of the electrochemical reduction of nitrate was studied. The product distribution depends on the nature of the metal only quantitatively, while the rate of the reduction was found to be about the same on all metals when the electrolysis was performed at the same rational potential (E(r)), which is the difference between the applied potential and the potential of zero charge of each metal. Based on these results it was concluded that the mechanism of nitrate reduction is the same for all cathodes studied.

The impact of spectator species on the interaction of H2O2 with platinum--implications for the oxygen reduction reaction pathways.

The impact of electrolyte constituents on the interaction of hydrogen peroxide with polycrystalline platinum is decisive for the understanding of the selectivity of the oxygen reduction reaction (ORR). Hydrodynamic voltammetry measurements show that while the hydrogen peroxide reduction (PRR) is diffusion-limited in perchlorate- or fluoride-containing solutions, kinetic limitations are introduced by the addition of more strongly adsorbing anions. The strength of the inhibition of the PRR increases in the order ClO4(-)≈ F(-) < HSO4(-) < Cl(-) < Br(-) < I(-) as well as with the increase of the concentration of the strongly adsorbing anions.

Toward highly stable electrocatalysts via nanoparticle pore confinement.

The durability of electrode materials is a limiting parameter for many electrochemical energy conversion systems. In particular, electrocatalysts for the essential oxygen reduction reaction (ORR) present some of the most challenging instability issues shortening their practical lifetime. Here, we report a mesostructured graphitic carbon support, Hollow Graphitic Spheres (HGS) with a specific surface area exceeding 1000 m(2) g(-1) and precisely controlled pore structure, that was specifically developed to overcome the long-term catalyst degradation, while still sustaining high activity.

Dissolution of platinum: limits for the deployment of electrochemical energy conversion?

Platinum stability: Dissolution of Pt, which is one major degradation mechanism in, for example, hydrogen/air fuel cells, was monitored under potentiodynamic and potentiostatic conditions. The highly sensitive and time-resolving dissolution monitoring enables the distinction between anodic and cathodic dissolution processes during potential transient and chronoamperometric experiments, and the precise quantification of the amount of dissolved Pt.

The influence of non-covalent interactions on the hydrogen peroxide electrochemistry on platinum in alkaline electrolytes.

The potential range of the transition region between the diffusion-limited reduction to oxidation of hydrogen peroxide depends strongly on the nature of the cation of the supporting alkaline electrolyte. Non-covalent interactions between the hydrated alkali metal cations and chemisorbed OH species on platinum influence the potential-dependent reaction kinetics.

Hydrogen peroxide electrochemistry on platinum: towards understanding the oxygen reduction reaction mechanism.

Understanding the hydrogen peroxide electrochemistry on platinum can provide information about the oxygen reduction reaction mechanism, whether H(2)O(2) participates as an intermediate or not. The H(2)O(2) oxidation and reduction reaction on polycrystalline platinum is a diffusion-limited reaction in 0.1 M HClO(4).

Development and integration of a LabVIEW-based modular architecture for automated execution of electrochemical catalyst testing.

This paper describes a system for performing electrochemical catalyst testing where all hardware components are controlled simultaneously using a single LabVIEW-based software application. The software that we developed can be operated in both manual mode for exploratory investigations and automatic mode for routine measurements, by using predefined execution procedures. The latter enables the execution of high-throughput or combinatorial investigations, which decrease substantially the time and cost for catalyst testing.

The particle size effect on the oxygen reduction reaction activity of Pt catalysts: influence of electrolyte and relation to single crystal models.

The influence of particle size on the oxygen reduction reaction (ORR) activity of Pt was examined in three different electrolytes: two acidic solutions, with varying anionic adsorption strength (HClO(4) < H(2)SO(4)); and an alkaline solution (KOH). The experiments show that the absolute ORR rate is dependent on the supporting electrolyte; however, the relationship between activity and particle size is rather independent of the supporting electrolyte. The specific activity (SA) toward the ORR rapidly decreases in the order of polycrystalline Pt > unsupported Pt black particles (~30 nm) > high surface area (HSA) carbon supported Pt nanoparticle catalysts (of various size between 1 and 5 nm).

Near-surface ion distribution and buffer effects during electrochemical reactions.

The near-surface ion distribution at the solid-liquid interface during the Hydrogen Oxidation Reaction (HOR)/Hydrogen Evolution Reaction (HER) on a rotating platinum disc electrode is demonstrated in this work. The relation between reaction rate, mass transport and the resulting surface pH-value is used to theoretically predict cyclic voltammetry behaviour using only thermodynamic and diffusion data obtained from the literature, which were confirmed by experimental measurements. The effect of buffer addition on the current signal, the surface pH and the ion distribution is quantitatively described by analytical solutions and the fragility of the surface pH during reactions that form or consume H(+) in near-neutral unbuffered solutions or poorly buffered media is highlighted.