Rapid Screening of Bimetallic Electrocatalysts for Oxygen Reduction in Acidic Media by Scanning Electrochemical Microscopy

Abstract

Additional bimetallic electrocatalysts for the oxygen reduction reaction ͑ORR͒ in acidic media were designed using a previously reported thermodynamic selection guide. The electrocatalyst mixtures were prepared in large arrays on glassy carbon substrates and the electrocatalytic activity was screened using scanning electrochemical microscopy ͑SECM͒. Activities were measured for a range of bimetallic combinations that showed a synergetic electrocatalytic effect during screening, including Au-V, Ag-V, Pd-Mn, and Pd-V. Upon initial screening, a highly active electrocatalytic combination consisting of 60:40 Pd-V was identified. Using rotating disk electrode ͑RDE͒ experiments, the high activity of this combination for the ORR in acidic media was confirmed when the electrocatalysts were supported on Vulcan carbon. The electrocatalytic activity of Pd-V was close to that exhibited by Pt, the electrocatalyst of choice for the ORR in acidic media, and thus is another example of a nonplatinum catalyst with high activity that follows the previous strategy for catalyst design.

In situ scanning electrochemical probe microscopy for energy applications

“…It was found that while not all combinations showed synergistic effects, several came close in performance to a conventional Pt electrode. 18,19 Similarly, Herrero et al studied the ORR at shape-controlled gold nanoparticles (NPs) and found that cubic NPs, which have a high abundance of (100) facets, were the most active, consistent with results obtained on macroscopic Au(100). 20,21 SECM has also been employed by Bard's group to study photocatalysts 22,23 for the conversion of solar energy to electricity or fuels and to screen porphyrins for use as Ru-free sensitizers for dye-sensitized solar cells (or Grätzel cells).…”

“…introduced the tip generation/substrate collection (TG/SC) mode to screen Pt-free electrocatalysts (various combinations of Pd, Au, and Ag with Co, [16][17][18] Ti, 17 V, 19 and/or Mn 19 ) for the ORR. It was found that while not all combinations showed synergistic effects, several came close in performance to a conventional Pt electrode.…”

Seeing Big with Scanning Electrochemical Microscopy

“…[1][2][3] Its applications include imaging patterned sensor surfaces, 4 measuring substance uptake and release from biological cells, 5 investigating very fast electrochemical reactions, 6 studying local corrosion, 7 screening electrocatalysts, 8 analyzing forensic samples, 9 and modifying surfaces. 10 The most common probes are amperometric microelectrodes produced by sealing a Pt wire of 10 or 25 μm diameter in a glass capillary and exposing the cross-section by grinding and polishing.…”

Investigation of Localized Catalytic and Electrocatalytic Processes and Corrosion Reactions with Scanning Electrochemical Microscopy (SECM)

“…Therefore, the FB mode cannot be applied for its investigation under most circumstances. Instead, the TG.SC mode was used for a number of investigations [116,[159][160][161][162]. The UME is positioned in a distance of 0.5-3 r T above the sample in an oxygen-free solution.…”

“…Such measurements have been used to screen catalyst libraries of metallic reduction catalysts [161,162]. In the latter case, an array of alloy dots made from Pd, Au, and Co with systematically varied composition was interrogated within one measurement.…”