Constant-distance mode SECM as a tool to visualize local electrocatalytic activity of oxygen reduction catalysts

Abstract

SummaryMultidimensional shearforce-based constant-distance mode scanning electrochemical microscopy (4D SF/CD-SECM) was utilized for the investigation of the activity distribution of oxygen reduction catalysts. Carbon-supported Pt model catalyst powders have been immobilized in recessed microelectrodes and compared to a spot preparation technique. Microcavities serve as platform for the binder-free catalyst sample preparation exhibiting beneficial properties for constant-distance mode SECM imaging concerning modified surface area and catalyst loading. The integration of the redox competition mode of SECM into the detection scheme of the 4D SF/CD mode is demonstrated for specifically adapting high-resolution SECM experiments to powder-based catalyst preparations.

Shearforce positioning of nanoprobe electrode arrays for scanning electrochemical microscopy experiments

“…Moreover, alternating current and tip position modulation permit rapid positioning with SECM setup without the need of complex instrumentation [17,25]. Within this large family of methods, shearforce detection has some peculiarities that make it convenient in corrosion analysis [5,26,27], visualization of local electrocatalytic activity [28] and characterization of living material [29][30][31][32]. The technology was also combined with SECM for micropatterning [33].…”

Onset potential determination at gas-evolving catalysts by means of constant-distance mode positioning of nanoelectrodes

“…A high-resolution constant-distance mode SECM setup was utilized for all experiments as described in [31,35]. Catalyst-filled MCEs were fixed up faced into a specifically designed measuring cell.…”

“…Microcavity electrodes (MCE) allow binder-free immobilization for gas-evolving catalysts as previously shown for different powder catalyst materials [21][22][23][24][25][26], quantitative investigation of OER catalysts [27,28], and as samples for SECM investigations [17,[29][30][31]. The effect of binder materials or conducting additives (e.g.…”

Using Cavity Microelectrodes for Electrochemical Noise Studies of Oxygen‐Evolving Catalysts

“…[2] We recently reported the use of perovskite-type oxides as effective catalysts for the OER in alkaline media. [5,11] Their main advantages lie in their small dimensions, which allow 1) working with very small amounts of the electroactive material (10 À7 -10 À8 g), [12] 2) pseudospherical diffusion and low capacitive contributions, and 3) minimized ohmic drop (due to low current values). Composite electrodes containing the material of interest are usually prepared by mixing and compacting the material powder into a pellet together with a conductive additive, such as graphite, and, in some cases, binder materials, for improved mechanical stability.…”

“…[7] CMEs were first introduced by Cha et al [8] as a tool for studying the electrochemical behavior of powder materials, including carbons, conducting polymers, battery materials, [9] double-layer capacitors, [10] and ORR electrocatalysts for fuel cells. [5,11] Their main advantages lie in their small dimensions, which allow 1) working with very small amounts of the electroactive material (10 À7 -10 À8 g), [12] 2) pseudospherical diffusion and low capacitive contributions, and 3) minimized ohmic drop (due to low current values). [13] Moreover, because no additives are needed, one can study the intrinsic properties of electroactive powder materials.…”