Screening of Oxygen Evolution Electrocatalysts by Scanning Electrochemical Microscopy Using a Shielded Tip Approach

Abstract

Oxygen evolution electrocatalysts in acidic media were studied by scanning electrochemical microscopy (SECM) in the substrate generation-tip collection (SG-TC) imaging mode with a 100 microm diam tip. Pure IrO2 and Sn(1-x)Ir(x)O2 combinatorial mixtures were prepared by a sol-gel route to form arrays of electrocatalyst spots. The experimental setup has been developed to optimize screening of electrocatalyst libraries under conditions where the entire array is capable of the oxygen evolution reaction (OER). The activity of individual spots was determined by reducing the interference from the reaction products of neighboring spots diffusing to the tip over the spot of interest. A gold layer deposited on the external wall of the SECM tip was used as a tip shield. In this study the shield was kept at a constant potential to reduce oxygen under mass transfer controlled conditions. The tip shield consumes oxygen coming from the neighbor spots in the array and enables the tip to correctly detect the activity of the spot below the tip. Simulations and experimental results are shown, demonstrating the effectiveness of the tip shield with the SG-TC setup in determining the properties of the composite materials and imaging arrays.

Discovering Ce-rich oxygen evolution catalysts, from high throughput screening to water electrolysis

“…[4][5][6][7][8][9][10][11] Ideally, the newly discovered materials will not only perform better under operational conditions, but display unique behaviors that contribute to the fundamental understanding of these complex reactions. Combinatorial methods have previously been used to search pseudoternary spaces for improved OER catalysts.…”

Rapid Characterization of Oxygen-Evolving Electrocatalyst Spot Arrays by the Substrate Generation/Tip Collection Mode of Scanning Electrochemical Microscopy with Decreased O2 Diffusion Layer Overlap

“…16−19 Here, we will focus on the SG/TC mode, which has been applied extensively to the quantification of H 2 O 2 from catalytic and electrocatalytic systems 16,19−24 and for gas-evolving reactions 25 such as the chlorine evolution reaction 6,26 and the oxygen evolution reaction. 27,28 In the SG/TC mode applied to the oxygen evolution reaction, the spots of the array are biased at a potential where water is oxidized at a steady state. The SECM tip acts as an amperometric sensor that collects the O 2 generated from each spot as the tip is moved in the XY plane.…”

Rapid Characterization of Hydrogen Evolution Electrocatalyst Spot Arrays by the Pulsed-Potential Substrate Generation/Tip Collection Mode of Scanning Electrochemical Microscopy

“…However, a problem arises here is the overlap of diffusion profiles of neighboring spots in the array [11,12]. A problem has been solved by developing a tipshielding layer (Au) outside the traditional SECM tip in order to consume diffused products coming from the neighbor spots in the array [13]. However, this method is time-consuming and requires preparing the particular tip, thus could not be extended to other research systems.…”