Single‐Entity Electrocatalysis of Individual “Picked‐and‐Dropped” Co₃O₄ Nanoparticles on the Tip of a Carbon Nanoelectrode

Abstract

Nano‐electrochemical tools to assess individual catalyst entities are critical to comprehend single‐entity measurements. The intrinsic electrocatalytic activity of an individual well‐defined Co3O4 nanoparticle supported on a carbon‐based nanoelectrode is determined by employing an efficient SEM‐controlled robotic technique for picking and placing a single catalyst particle onto a modified carbon nanoelectrode surface. The stable nanoassembly is microscopically investigated and subsequently electrochemically characterized. The hexagonal‐shaped Co3O4 nanoparticles demonstrate size‐dependent electrochemical activity and exhibit very high catalytic activity with a current density of up to 11.5 A cm−2 at 1.92 V (vs. RHE), and a turnover frequency of 532±100 s−1 at 1.92 V (vs. RHE) towards catalyzing the oxygen evolution reaction.

A Review on Experimental Identification of Active Sites in Model Bifunctional Electrocatalytic Systems for Oxygen Reduction and Evolution Reactions

“…The individual Co 3 O 4 nanoparticles demonstrated a high catalytic size‐depended activity towards the OER performed in an alkaline medium, as well as high TOF values of 532±100 s −1 at 1.92 V vs. RHE. In addition, structural changes of the single hexagonal‐shaped Co 3 O 4 particles from crystalline to amorphous were observed at high anodic OER overpotentials [108] …”

“…This robotic technique allows to select the individual particle by picking it up to support onto the surface of the CNE under SEM imaging (Figure 8). The main advantage of this “picking‐and‐placing” method is the control of the particle orientation on the CNE surface (Figure 8f‐i) [108] . Using the above‐described technique, differently sized single nanoparticles of the hexagonal‐shaped Co 3 O 4 supported on the CNE were investigated for the OER.…”

“…The particles were synthesized by a wet colloidal synthesis, with the size variation from 180 to 300 nm [109] . The CNE was produced by the pyrolytic decomposition of butane gas inside the pulled quartz nanopipettes [108] . The individual Co 3 O 4 nanoparticles demonstrated a high catalytic size‐depended activity towards the OER performed in an alkaline medium, as well as high TOF values of 532±100 s −1 at 1.92 V vs. RHE.…”

Single Particle Nanoelectrochemistry Reveals the Catalytic Oxygen Evolution Reaction Activity of Co3O4 Nanocubes

“…[9] Recently,w er eported am ethod to attach and investigate well-defined hexagonal-shaped single Co 3 O 4 nanoparticles to the tip of acarbon-based nanoelectrode (CNE) using arobotic micromanipulator inside the scanning electron microscope (SEM). [10] SECCM has been employed for determining the structure-activity correlation of different electrochemically active surfaces and nanomaterials,o ffering as patial resolution down to single nanoparticles. [11,12] Investigating the droplet landing areas of SECCM by means of SEM or TEM allows to derive structure-activity correlation.…”

Electrochemical synthesis of core–shell nanoparticles by seed-mediated selective deposition

“…It is well known that the electrochemical activity of surfactant covered nanoparticles is low. 14,15 For electrocatalytic application, a costly pretreatment process (thermolysis or reduction of surfactants to carbonaceous matter in H 2 ) is mandated. 16 To bypass this problem, direct electrochemical syntheses of surfactant-free nanomaterials have recently been developed; [17][18][19] however, investigations toward electrochemical synthesis of core-shell nanoparticles are rare yet.…”