Activation Matters: Hysteresis Effects during Electrochemical Looping of Colloidal Ag Nanowire Catalysts

Abstract

Colloidal electrocatalysts are commonly synthesized using organic capping agents (surfactants), which control the size distribution and shape of the resulting nano-objects and prevent them from agglomerating during and after synthesis. However, the presence of a surfactant shell on the catalyst is detrimental, as the resulting performance of the electrocatalyst depends crucially on the ability of reactants to access active surface sites. Techniques for post-synthesis deprotection are therefore mandatory for removing the capping agents from the otherwise blocked reactions sites without compromising the structural integrity of the nano-catalysts. Herein, we present silver nanowires (Ag-NWs) -produced via PVP-assisted polyol synthesis -as effective catalysts for the electrochemical CO2 reduction reaction (ec-CO2RR), which reach Faradaic efficiencies close to 100% for CO formation after deprotection by a so-called 'electrochemical looping' (ec-l) pretreatment.Electrochemical looping refers to a sequence of potentiostatic CO electrolysis experiments that exhibit well-defined starting (Estart), vertex (Evertex), and end potentials (Eend). The resulting product distribution undergoes a profound hysteresis in the forward and corresponding backward run of the electrochemical looping experiment, thus pointing to an effective deprotection of the catalyst as evidenced by post-electrolysis XPS inspection. These results can be considered as prime example demonstrating the importance of the catalyst's 'history' for the resulting ec-CO2RR performance.These transient (non-steady-state) effects are crucial in particular for the initial stage of the CO2 electrolysis reaction and for catalyst screening approaches carried out on the time scale of hours.

Metal‐Organic Framework Hybrids Aid Metabolic Profiling for Colorectal Cancer

“…The successful reduction by PVP was attributed to its strong capping capability and surface arrangement improvement, during the nucleation and growth of Pt nanoparticles. [ 33 ] Therefore, we concluded that the PVP and silica intermediates were critical for the structural conservation and facile functionalization during the layer‐by‐layer assembling.…”

Visualisation and quantification of flooding phenomena in gas diffusion electrodes (GDEs) used for electrochemical CO2 reduction: A combined EDX/ICP–MS approach

“…To prepare a catalyst ink, 4.5 mg of silver nanowires (Ag NWs, prepared as described in [31]) 0.8 mg of carbon black (VULCAN™ VXC72R, Cabot) were separately dispersed in 20 cm 3 isopropanol (BASF SE, assay ≥ 99.0%) by half hour of sonication. Both suspensions were intermixed and sonicated for an additional half hour, then dried by a rotary evaporator (Büchi R210, 40 ºC, 65 mbar).…”

Graphdiyne‐Stabilized Silver Nanoparticles as an Efficient Electrocatalyst for CO2 Reduction

“…[ 18–20 ] A series of Ag‐based nanowires (Ag‐NWs) has been prepared as electrocatalysts for CO 2 ‐to‐CO reduction, which achieved high Faradaic efficiencies (FEs), mostly due to the increased electrochemically active surface area. [ 21–23 ] Mauzeroll and coworkers biosynthesized Ag‐based nanorings (Ag‐NRs), which could reach an FE of 95.0% for the conversion of CO 2 to CO. [ 24 ] Polyansky's group reported a Ag nanocoral catalyst with a high surface area, displaying a low overpotential of 0.37 V and high current efficiency of 95% for CO 2 ‐to‐CO reduction catalysis. [ 25 ] In addition, some other nanoporous Ag‐based (np‐Ag) catalysts with diverse nanostructures have also been investigated for electrochemically reducing CO 2 to CO with significantly enhanced catalytic efficiency.…”

“…The (111) plane of AgNPs is regarded as the most promising plane for reducing CO 2 . [ 21,26,28 ] The in situ anchoring of AgNPs onto the GDY template with intimate contact can highly increase the exposure of the Ag (111) plane of the AgNPs and fully increase the surface charge density of AgNPs, thus tremendously enhancing its performance for the electrocatalytic reduction of CO 2 to CO.…”