Electrochemical Detection of Individual Catalytic and Redox-Inactive Materials
Authors: Roehrich Brian , Sepunaru Lior 
Published: December 2020

Using low noise electronics and micro-electrodes we can now detect single analytes in solution, one at a time.1,2 In this talk, we will briefly cover recent discoveries in the field of single entity electrochemistry and show that both electroactive and electro-inactive materials can be detected using complementary approaches.3,4 However, some strong limitations in this field persist. In the case of electroactive entities, in order to detect the single entity above the electrochemical noise level, a careful choice of the analyte that differs in its physical properties from the electrode is needed. Here, we show that an active particle-active electrode composed of the same material can provide mechanistic insight into electrochemical reactions.5 Current transients obtained during hydrogen evolution allow simultaneous measurement of the Pt catalyst over different length scales, size dependency suggests H atom intercalation as a catalytic deactivation mechanism.

In the case of redox-inactive materials, a different analytical problem exists. The location of the adsorbed individual material at the electrode surface influences the magnitude of the electrochemical signal being blocked during a steady-state flux of a redox probe towards the electrode.6,7 Our recent discovery shows that coupling the electrochemical reaction to a homogeneous rate-limiting chemical reaction offers a platform for high precision measurements. Using both finite element simulations and experimental statistical analysis we provide guiding rules for sizing redox-inactive materials with high analytical precision under various conditions such as analyte and electrode size and analyte concentration.

References:

(1) M. Crooks, R. Concluding Remarks: Single Entity Electrochemistry One Step at a Time. Faraday Discuss.
2016, 193 (0), 533–547. https://doi.org/10.1039/C6FD00203J.

(2) V. Sokolov, S.; Eloul, S.; Kätelhön, E.; Batchelor-McAuley, C.; G. Compton, R. Electrode–Particle Impacts: A Users Guide. Phys. Chem. Chem. Phys.
2017, 19 (1), 28–43. https://doi.org/10.1039/C6CP07788A.

(3) Bard, A. J.; Zhou, H.; Kwon, S. J. Electrochemistry of Single Nanoparticles via Electrocatalytic Amplification. Isr. J. Chem.
2010, 50 (3), 267–276. https://doi.org/10.1002/ijch.201000014.

(4) Quinn, B. M.; van’t Hof, P. G.; Lemay, S. G. Time-Resolved Electrochemical Detection of Discrete Adsorption Events. J. Am. Chem. Soc.
2004, 126 (27), 8360–8361. https://doi.org/10.1021/ja0478577.

(5) Roehrich, B.; Sepunaru, L. Nanoimpacts at Active and Partially Active Electrodes: Insights and Limitations. Angew. Chem. Int. Ed.
n/a (n/a). https://doi.org/10.1002/anie.202007148.

(6) Fosdick, S. E.; Anderson, M. J.; Nettleton, E. G.; Crooks, R. M. Correlated Electrochemical and Optical Tracking of Discrete Collision Events. J. Am. Chem. Soc.
2013, 135 (16), 5994–5997. https://doi.org/10.1021/ja401864k.

(7) Deng, Z.; Elattar, R.; Maroun, F.; Renault, C. In Situ Measurement of the Size Distribution and Concentration of Insulating Particles by Electrochemical Collision on Hemispherical Ultramicroelectrodes. Anal. Chem.
2018, 90 (21), 12923–12929. https://doi.org/10.1021/acs.analchem.8b03550.