Browsing by Author "Wilde, Patrick"

Now showing 1 - 5 of 5
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    Cascade Reactions in Nanozymes: Spatially Separated Active Sites inside Ag-Core−Porous-Cu-Shell Nanoparticles for Multistep Carbon Dioxide Reduction to Higher Organic Molecules
    (Journal of the American Chemical Society, 2019) O’Mara, Peter B.; Wilde, Patrick; Benedetti, Tania M.; Andrones, Corina; Cheong, Soshan; Gooding, Justin; Tilley, Richard D.; Schuhmann, Wolfgang
    Enzymes can perform complex multistep cascade reactions by linking multiple distinct catalytic sites via substrate channeling. We mimic this feature in a generalized approach with an electrocatalytic nanoparticle for the carbon dioxide reduction reaction comprising a Ag core surrounded by a porous Cu shell, providing different active sites in nanoconfined volumes. The architecture of the nanozyme provides the basis for a cascade reaction, which promotes C−C coupling reactions. The first step occurs on the Ag core, and the subsequent steps on the porous copper shell, where a sufficiently high CO concentration due to the nanoconfinement facilitates C−C bond formation. The architecture yields the formation of n-propanol and propionaldehyde at potentials as low as −0.6 V vs RHE.
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    Combining Nanoconfinement in Ag Core/Porous Cu Shell Nanoparticles with Gas Diffusion Electrodes for Improved Electrocatalytic Carbon Dioxide Reduction
    (ChemElectroChem, 2021) Junqueira, João R. C.; O’Mara, Peter B.; Wilde, Patrick; Dieckhöfer, Stefan; Benedetti, Tania M.; Andronescu, Corina; Tilley, Richard D.; Gooding, J. Justin; Schuhmann, Wolfgang
    Bimetallic silver-copper electrocatalysts are promising materials for electrochemical CO2 reduction reaction (CO2RR) to fuels and multi-carbon molecules. Here, we combine Ag core/porous Cu shell particles, which entrap reaction intermediates and thus facilitate the formation of C2+ products at low overpotentials, with gas diffusion electrodes (GDE). Mass transport plays a crucial role in the product selectivity in CO2RR. Conventional Hcell configurations suffer from limited CO2 diffusion to the reaction zone, thus decreasing the rate of the CO2RR. In contrast, in the case of GDE-based cells, the CO2RR takes place under enhanced mass transport conditions. Hence, investigation of the Ag core/porous Cu shell particles at the same potentials under different mass transport regimes reveals: (i) a variation of product distribution including C3 products, and (ii) a significant change in the local OH- activity under operation.
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    Influence of Temperature and Electrolyte Concentration on the Structure and Catalytic Oxygen Evolution Activity of NiFe LDH
    (Chemistry–A European Journal, 2018) Andronescu, Corina; Seisel, Sabine; Wilde, Patrick; Barwe, Stefan; Masa, Justus; Schuhmann, Wolfgang
    NiFe layered double hydroxide (LDH) is inarguably the most active contemporary catalyst for the oxygen evolution reaction under alkaline conditions. However, the ability to sustain unattenuated performance under challenging industrial conditions entailing high corrosivity of the electrolyte (≈30 wt. % KOH), high temperature (>80 °C) and high current densities (>500 mA cm−2) is the ultimate criterion for practical viability. This work evaluates the chemical and structural stability of NiFe LDH at conditions akin to practical electrolysis, in 30 % KOH at 80 °C, however, without electrochemical polarization, and the resulting impact on the OER performance of the catalyst. Post-analysis of the catalyst by means of XRD, TEM, FT-IR, and Raman spectroscopy after its immersion into 7.5 m KOH at 80 °C for 60 h revealed a transformation of the structure from NiFe LDH to a mixture of crystalline β-Ni(OH)2 and discrete predominantly amorphous FeOOH containing minor non-homogeneously distributed crystalline domains. These structural and compositional changes led to a drastic loss of the OER activity. It is therefore recommended to study catalyst stability at industrially relevant conditions.
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    Is Cu instability during the CO2 reduction reaction governed by the applied potential or the local CO concentration?
    (Chemical science, 2021) Wilde, Patrick; O'Mara, Peter B.; Junqueira, Joao R. C.; Tarnev, Tsvetan; Benedetti, Tania M.; Andronescu, Corina; Chen, Yen-Ting; Tilley, Richard D.; Schuhmann, Wolfgang; Gooding, J. Justin
    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 w
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    Oxygen Evolution Electrocatalysis of a Single MOF-derived Composite Nanoparticle on the tip of a Nanoelectrode
    (Angewandte Chemie International Edition, 2019) Aiyappa, Harshitha Barike; Wilde, Patrick; QuasT, Thomas; Masa, Justus; Andronescu, Corina; Schuhmann, Wolfgang
    Determination of the intrinsic electrocatalytic activity of nanomaterials by means of macroelectrode techniques is compromised by ensemble and film effects. Here, a unique “particle on a stick” approach is used to grow a single metal–organic framework (MOF; ZIF-67) nanoparticle on a nanoelectrode surface which is pyrolyzed to generate a cobalt/nitrogen-doped carbon (CoN/C) composite nanoparticle that exhibits very high catalytic activity towards the oxygen evolution reaction (OER) with a current density of up to 230 mA cm−2 at 1.77 V (vs. RHE), and a high turnover frequency (TOF) of 29.7 s−1 at 540 mV overpotential. Identical location transmission electron microscopy (IL-TEM) analysis substantiates the “self-sacrificial” template nature of the MOF, while post-electrocatalysis studies reveal agglomeration of Co centers within the CoN/C composite during the OER. “Single-entity” electrochemical analysis allows for deriving the intrinsic electrocatalytic activity and furnishes insight into the transient behavior of the electrocatalyst under reaction conditions.