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Cu-based catalysts have shown structural instability during the electrochemical CO2 reduction reaction (CO2RR). However, studies on monometallic Cu catalysts do not allow a nuanced differentiation between the contribution of the applied potential and the local concentration of CO as the reaction intermediate since both are inevitably linked. We first use bimetallic Ag-core/porous Cu-shell nanoparticles, which utilise nanoconfinement to generate high local CO concentrations at the Ag core at potentials at which the Cu shell is still inactive for the CO2RR. Using operando liquid cell TEM in combination with ex situ TEM, we can unequivocally confirm that the local CO concentration is the main source for the Cu instability. The local CO concentration is then modulated by replacing the Ag-core with a Pd-core which further confirms the role of high local CO concentrations. Product quantification during CO2RR reveals an inherent trade-off between stability, selectivity and activity in both systems., The stability of bimetallic AgCu and PdCu catalysts for electrochemical CO2RR is investigated using the combination of operando and ex situ TEM. The local CO concentration is identified as the main link between activity, stability and selectivity.

Gas diffusion electrodes (GDE) obtained by sputtering metal films on polytetrafluoroethylene (PTFE) membranes are among the most performant electrodes used to electrochemically reduce CO₂. The present work reveals several essential aspects for fabricating performant PTFE-based gas diffusion electrodes (GDEs) for CO₂ electroreduction (CO₂R). We show that adding an additive layer (a mixture of carbon and Nafion™ or Nafion™ only) is required for stabilizing the metal catalyst film (Cu), deposited via sputtering on the PTFE membrane, during the CO₂R experiments. We found that the PTFE membrane thickness used in the GDE fabrication plays an essential role in electrode performance. The quantification of the products formed during the CO₂R conducted in a flow-cell electrolyzer revealed that on thinner membranes, CO₂R is the dominant process while on thicker ones, the H₂ formation is promoted. Thus, the PTFE membrane influences the CO₂ transport to the catalyst layer and can be used to promote the CO₂R while maintaining a minimum H₂ production.

Mitigating high energy costs related to sustainable H₂ production via water electrolysis is important to make this process commercially viable. Possible approaches are the investigation of low-cost, highly active oxygen evolution reaction (OER) catalysts and the exploration of alternative anode reactions, such as the electrocatalytic isopropanol oxidation reaction (iPOR) or the glycerol oxidation reaction (GOR), offering the possibility of simultaneously lowering the anodic overpotential and generating value-added products. A suitable class of catalysts are non-noble metal-based perovskites with the general formula ABO₃, featuring rare-earth metal cations at the A- and transition metals at the B-site. We synthesised a series of LaFe₁₋ₓCoₓO₃ materials with x=0–0.70 by automated co-precipitation at constant pH and subsequent calcination at 800 °C. X-ray diffraction studies revealed that the phase purity was preserved in samples with x≤0.3. The activity towards the OER, iPOR, and GOR was investigated by rotating disk electrode voltammetry, showing a relation between structure and metal composition with the activity trends observed for the three reactions. Additionally, GOR product analysis via high-performance liquid chromatography (HPLC) was conducted after 24 and 48 h electrolysis in a circular flow-through cell setup, pointing out a trade-off between activity and selectivity.

Gas diffusion electrodes (GDE) obtained by sputtering metal films on polytetrafluoroethylene (PTFE) membranes are among the most performant electrodes used to electrochemically reduce CO2. The present work reveals several essential aspects for fabricating performant PTFE-based gas diffusion electrodes (GDEs) for CO2 electroreduction (CO2R). We show that adding an additive layer (a mixture of carbon and Nafion™or Nafion™ only) is required for stabilizing the metal catalyst film (Cu), deposited via sputtering on the PTFE membrane, during the CO2R experiments. We found that the PTFE membrane thickness used in the GDE fabrication plays an essential role in electrode performance. The quantification of the products formed during the CO2R conducted in a flow-cell electrolyzer revealed that on thinner membranes, CO2R is the dominant process while on thicker ones, the H2 formation is promoted. Thus, the PTFE membrane influences the CO2 transport to the catalyst layer and can be used to promote the CO2R while maintaining a minimum H2 production.

Developing highly efficient and selective electrocatalysts for the CO2 reduction reaction to produce value-added chemicals has been intensively pursued. We report a series of CuxOyCz nanostructured electrocatalysts derived from a Cu-based MOF as porous self-sacrificial template. Blending catalysts with polytetrafluoroethylene (PTFE) on gasdiffusion electrodes (GDEs) suppressed the competitive hydrogen evolution reaction. 25 to 50 wt % teflonized GDEs exhibited a Faradaic efficiency of & 54 % for C2+ products at -80 mAcm-2. The local OH- ions activity of PTFE-modified GDEs was assessed by means of closely positioning a Pt-nanoelectrode. A substantial increase in the OH-/H2O activity ratio due to the locally generated OH@ ions at increasing current densities was determined irrespective of the PTFE amount.

Die Entwicklung hocheffizienter und selektiver Elektrokatalysatoren für die CO2-Reduktionsreaktion zur Herstellung von Chemikalien mit hohem Mehrwert wird intensiv untersucht. Wir berichten über eine Reihe von CuxOyCz nanostrukturierten Elektrokatalysatoren, die von einem MOF auf Cu-Basis als poröses selbstopferndes Templat abgeleitet sind. Die Mischung der Katalysatoren mit Polytetrafluorethylen (PTFE) auf Gasdiffusionselektroden (GDEs) unterdrückte die konkurrierende Wasserstoffentwicklungsreaktion. Mit 25 bis 50 Gew.-% teflonisierter GDEs wurde bei einer Stromdichte von 80 mAcm-2 eine Faradayeffizienz von ~54% für C2+ Produkte erzielt. Die lokale OH--Ionenaktivität der PTFE-modifizierten GDEs wurde durch die Positionierung einer Pt-Nanoelektrode in unmittelbarer Nähe der GDE bestimmt. Unabhängig von der PTFE-Menge wurde ein erheblicher Anstieg des OH-/H2O-Aktivitätsverhältnisses aufgrund der lokal erzeugten OH--Ionen bei steigenden Stromdichten festgestellt.

Co3O4 nanocubes are evaluated concerning their intrinsic electrocatalytic activity towards the oxygen evolution reaction (OER) by means of single-entity electrochemistry. Scanning electrochemical cell microscopy (SECCM) provides data on the electrocatalytic OER activity from several individual measurement areas covering one Co3O4 nanocube of a comparatively high number of individual particles with sufficient statistical reproducibility. Single-particle-on-nano-electrode measurements of Co3O4 nanocubes provide an accelerated stress test at highly alkaline conditions with current densities of up to 5.5 Acm-2, and allows to derive TOF values of up to 2.8 X104 s-1 at 1.92 V vs. RHE for surface Co atoms of a single cubic nanoparticle. Obtaining such high current densities combined with identical-location transmission electron microscopy allows monitoring the formation of an oxy(hydroxide) surface layer during electrocatalysis. Combining two independent single-entity electrochemistry techniques provides the basis for elucidating structure–activity relations of single electrocatalyst nanoparticles with well-defined surface structure.

Electroreduction of CO2 to multi‐carbon products has attracted considerable attention as it provides an avenue to high‐density renewable energy storage. However, the selectivity and stability under high current densities are rarely reported. Herein, B‐doped Cu (B‐Cu) and B‐Cu‐Zn gas diffusion electrodes (GDE) were developed for highly selective and stable CO2 conversion to C2+ products at industrially relevant current densities. The B‐Cu GDE exhibited a high Faradaic efficiency of 79 % for C2+ products formation at a current density of −200 mA cm−2 and a potential of −0.45 V vs. RHE. The long‐term stability for C2+ formation was substantially improved by incorporating an optimal amount of Zn. Operando Raman spectra confirm the retained Cu+ species under CO2 reduction conditions and the lower overpotential for *OCO formation upon incorporation of Zn, which lead to the excellent conversion of CO2 to C2+ products on B‐Cu‐Zn GDEs.

Cu-based catalysts have shown structural instability during the electrochemical CO₂reduction reaction (CO₂RR). However, studies on monometallic Cu catalysts do not allow a nuanced differentiation between the contribution of the applied potential and the local concentration of CO as the reaction intermediate since both are inevitably linked. We first use bimetallic Ag-core/porous Cu-shell nanoparticles, which utilise nanoconfinement to generate high local CO concentrations at the Ag core at potentials at which the Cu shell is still inactive for the CO₂RR. Usingoperandoliquid cell TEM in combination withex situTEM, we can unequivocally confirm that the local CO concentration is the main source for the Cu instability. The local CO concentration is then modulated by replacing the Ag-core with a Pd-core which further confirms the role of high local CO concentrations. Product quantification during CO₂RR reveals an inherent trade-off between stability, selectivity and activity in both systems. OA platinum

Nur die Bestimmung der intrinsischen elektrokatalytischen Aktivität einzelner Katalysatorpartikel liefert die grundlegenden Erkenntnisse, neue und hochaktive Katalysatormaterialien auf Basis gut verfügbarer Materialien mit guter Stabilität zu entdecken. Die hier vorgestellten Methoden sind unabdingbar, um Struktur-Aktivitäts-Beziehungen aufzuklären und so die Basis für das rationale Design geeigneter Katalysatormaterialien aufzubauen., UNIKATE: Berichte aus Forschung und Lehre, no. 57Katalyse: Alles andere als oberflächlich, p. 73

The use of renewable energy by means of electrochemical techniques by converting H\(_2\)O, CO\(_2\) and N\(_2\) into chemical energy sources and raw materials, is the basis for securing a future sustainable "green" energy supply. Some weaknesses and inconsistencies in the practice of determining the electrocatalytic performance, which prevents a rational bottom-up catalyst design, are discussed. Large discrepancies in material properties as well as in electrocatalytic activity and stability become obvious when materials are tested under the conditions of their intended use as opposed to the usual laboratory conditions. They advocate for uniform activity/stability correlations under application-relevant conditions, and the need for a clear representation of electrocatalytic performance by contextualization in terms of functional investigation or progress towards application is emphasized.

Carbon is a frequently used electrode material and an important additive in catalyst films. Its corrosion is often reported during electrocatalysis at high anodic potentials, especially in acidic electrolyte. Investigation of the carbon corrosion in alkaline environment is difficult due to the CO2/CO3 2- equilibrium. We report the on-line determination of electrolysis products generated on NixB/C hybrid electrocatalysts in alkaline electrolyte at anodic potentials using differential electrochemical mass spectrometry (DEMS). NixB/C catalyst films were obtained from mixtures containing different ratios of NixB and benzoxazine monomers followed by polymerization and pyrolysis. The impact of the composition of the electrocatalyst on the dominant electrolysis process allows to distinguish between the oxygen evolution reaction and carbon corrosion using DEMS results as well as the catalyst surface composition evaluated from X-ray photoelectron spectra. At the imposed highly oxidative conditions, an increasing amount of NixB in the electrocatalyst leads to a suppression of carbon corrosion.

Owing to their intrinsic amplifying effect together with their temporal resolution, field‐effect transistors (FETs) are gaining momentum for the detection of different biomolecules at ultra‐low concentration levels such as, for example, neurotransmitters, particularly if the concentration level of the analyte is below the detection limit of commonly used electrochemical sensing methods. We demonstrate the fabrication of a spearhead reduced graphene oxide (rGO)‐based FET. The fabrication of the rGO‐based FET by means of an electrochemical pulse deposition technique enables a controllable process including both the deposition and reduction of the deposited graphene oxide between two carbon nanoelectrodes to form the channel of the rGO‐based FET. While using double‐barrel carbon nanoelectrodes, the as‐produced FETs offer new possibilities in terms of their applicability in very small volumes as well as the option of being positioned close to the desired measurement region. The fabrication process was evaluated and optimized to obtain rGO‐based FETs with high performance. The as‐fabricated devices were evaluated in terms of sensitivity and selectivity towards dopamine. The tested devices not only showed high sensitivity towards dopamine with a linear response ranging from 1 nM to 1 \(\mu\)M, but also maintained a similar sensing performance in the presence of 500 \(\mu\)M ascorbic acid.