Modified Floating Electrode Apparatus for Advanced Characterization of Oxygen Reduction Reaction Electrocatalysts

Herein a modified floating electrode (MFE) approach for investigating the electrochemical phenomena at a gas/electrode/liquid reaction interface is introduced. Such investigation is in sharp contrast to conventional electrochemical techniques, which measure the properties of electrode/liquid interfaces. MFE is based on an apparatus that enables electrocatalytic conversion under enhanced mass transport of reactant gas. This is enabled by the floating regime of the working electrode that presents a low mass transport barrier for the gas. The present MFE is designed to take the advantage of transmission electron microscopy (TEM) grids with a deposited electrocatalyst of choice, to be used as working electrodes. The applicability of MFE is demonstrated on the example of oxygen reduction reaction (ORR), an essential segment in the sector of electrochemical energy conversion. The approach is validated on two state-of-the-art industrial benchmarks ORR electrocatalysts, a carbon-supported platinum (Pt/C) nanoparticulated electrocatalyst and an alloyed counterpart (Pt-Co/C). It is shown that MFE enables acquisition of the two most vital catalyst features in one measurement sequence. Firstly, it allows for rapid electrochemical performance measurements of potential ORR electrocatalysts under high oxygen transport, specifically high current densities. Secondly, it enables the local characterization of nanostructural events via identical location transmission electron microscopy (IL-TEM).