Photonic Curing: Activation and Stabilization of MetalMembrane Catalysts (MMCs) for the Electrochemical Reduction of CO 2

Photonic curing, an exposure of matter to intense and short (mu s) light pulses, is herein demonstrated as an effective and versatile method to activate and stabilize electrocatalysts for the electrochemical reduction of CO2. Catalyst preparation by colloidal synthesis often makes use of surfactants (capping agents) that control the size and morphology of target nano objects during and after their synthesis. However, this approach can severely compromise the catalytic properties of the as-synthesized nanomaterials. Photonic curing is suitable to gently remove surfactants from the catalyst surface without severely altering its overall structural properties (e.g., surface faceting), thereby increasing the abundance of these surface active sites that can participate in the desired (electro)catalytic reaction. This catalyst activation is exemplarily demonstrated on the basis of Cu nanowire (Cu-NW) catalysts synthesized by an oleylamine route and transferred to a glassy carbon (GC) support electrode. Although the 3D networks of the as-synthesized Cu-NW catalysts predominantly produce hydrogen as the product of the electrolysis reaction, photonically cured Cu-NAATs, denoted hereinafter as Cu metal membrane catalysts (MMCs), show a high selectivity toward ethylene formation, reaching a Faradaic efficiency of FEC2H4 = 42.4% (J(C2H4) = -7.8 mA cm(-2), E = -1.1 V vs RHE). This high ethylene yield can even be maintained during prolonged electrolysis of 110 h. A further beneficial effect of the photonic curing treatment is related to the substantially increased mechanical stabilization of the Cu-NW film on the support electrode induced by a "mild" sintering of Cu-NWs, which remains locally confined to their points of contact. A loss of catalyst material or a delamination of the catalyst film from the support electrode during massive gas evolution can thus be prevented.