Hot-Tip Scanning Electrochemical Microscopy: Theory and Experiments Under Positive and Negative Feedback Conditions

Abstract

Hot-tip scanning electrochemical microscopy (HT-SECM) is a novel surface characterization technique utilizing an alternating current (ac) polarized disk microelectrode as a probe. A high-frequency (∼100 MHz) ac waveform applied between the tip and a counter electrode causes the resistive heating of the surrounding electrolyte solution that leads also to the electrothermal fluid flow (ETF). The effects of the temperature and the convection driven by the ETF result in the increased rate of mass transfer of the redox species. In this paper, HT-SECM was studied in positive and negative feedback modes, for which approach curves and cyclic voltammograms were recorded. The experimental data showed that the use of a hot tip leads to a more pronounced feedback compared to that at room temperature. Numerical simulations performed in COMSOL Multiphysics supported the experimental findings. Additional analytical approximations were developed that could be used to predict the faradaic response in HT-SECM experiments. Finally, a possible contribution to the current from the Soret effect was studied theoretically. A good understanding of HT-SECM was achieved, both experimentally and theoretically, suggesting that this methodology could be applied to investigate electrode kinetics under the conditions of elevated temperature and increased rate of mass transfer.

Scanning Electrochemical Microscopy of Electrically Heated Wire Substrates

“…Boika et al have made use of this effect by employing heated UMEs as probes in SECM. They refer to this as "hot tip SECM" [31,32]. Other groups have investigated the impact of heated samples, showing that temperature impacts the contrast between conductive/non-conductive areas in feedback mode [33], as well as the possibility of altering the activity of immobilized enzymes on surfaces during SECM studies [34].…”

Hot-SWV: Square Wave Voltammetry with Hot Microelectrodes

“…We described the construction of this filter in a previous report. 24,25 Experiments in Isothermally Heated Solutions. The experiments with isothermally heated solutions were performed by using a water-jacketed electrochemical cell connected to a Huber temperature-controlled recirculation water bath (model K6, Huber, Offenburg, Germany).…”

“…To determine the electrode temperature, we recorded steady-state voltammograms (SS-CVs) corresponding to the 25 ). Square Wave Voltammetric Measurements.…”

Impact of Plasmonic Photothermal Effects on the Reactivity of Au Nanoparticle Modified Graphene Electrodes Visualized Using Scanning Electrochemical Microscopy

“…When investigating the effects of generated plasmons on reactivity changes, reports in literature commonly propose photothermal processes and hot electron/hole transfer as sources of the observed effects. ,,− However, reports do not always agree on the relative role of these two factors: for example, the conversion of 4-nitrobenzenethiol to the amino derivative has been reported as both deriving from photothermal effects and not. − Only recently, studies have sought to determine the relative contributions of these factors. , This includes the use of SECM by the Willets group for monitoring hot-carrier versus photothermal effects caused by nanoparticle irradiation on photoelectrochemical interfaces . Because SECM is able to quantify site specific electron transfer kinetics, , and responds to temperature effects at the tip, we turned to this technique to investigate the coupling of graphene with metallic nanoparticles.…”

“…14,25 This includes the use of SECM by the Willets group for monitoring hot-carrier versus photothermal effects caused by nanoparticle irradiation on photoelectrochemical interfaces. 26 Because SECM is able to quantify site specific electron transfer kinetics, 27,28 and responds to temperature effects at the tip, 29 we turned to this technique to investigate the coupling of graphene with metallic nanoparticles. Herein, we explore a new avenue of SECM studies of how underlying nanoparticles impact the reactivity of a surface modifying layer for both outer-sphere mediator and innersphere electrocatalytic reactions.…”