Microwave activation of electrochemical processes: convection, thermal gradients and hot spot formation at the electrode∣solution interface

Marken, Frank; Tsai, Yu-Chen; Coles, Barry A.; Matthews, Steven L.; Compton, Richard G.

doi:10.1039/b003413o

Cited by 54 publications

(56 citation statements)

References 16 publications

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“…Figure 11) and placed in a microwave cavity. Under these conditions microwave radiation is (self-)focussed into a small high intensity region in the vicinity of the electrode, but with a high temperature region (or hot spot) in the solution phase some ten microns more away from the electrode surface [138].…”

Section: Microwave Thermally and Laser Activated Electroanalytical mentioning

confidence: 99%

Electroanalysis at Diamond‐Like and Doped‐Diamond Electrodes

2003

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Diamond as a high performance material occupies a special place due to its in many ways extreme properties, e.g., hardness, chemical inertness, thermal conductivity, optical properties, and electric characteristics. Work mainly over the last decade has shown that diamond also occupies a special place as an electrode material with interesting applications in electroanalysis. When made sufficiently electrically conducting for example by boron-doping, −thin film× and −free ± standing× diamond electrodes exhibit remarkable chemical resistance to etching, a wide potential window, low background current responses, mechanical stability towards ultrasound induced interfacial cavitation, a low −stickiness× in adsorption processes, and a high degree of −tunability× of the surface properties. This review summarizes some of the recent work aimed at applying conductive (boron-doped) diamond electrodes to improve procedures in electroanalysis.

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Section: Microwave Thermally and Laser Activated Electroanalytical mentioning

confidence: 99%

Electroanalysis at Diamond‐Like and Doped‐Diamond Electrodes

2003

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“…Local temperatures can exceed the boiling point of the solvent, with temperatures of 150 8C reported in aqueous systems [52] and 118 8C in acetonitrile [56]. The heating process itself was investigated using the two-electron reduction of the methyl viologen di-cation in aqueous solution [51]. It was shown that microwave activation achieves i) high temperatures in the vicinity of the electrode, ii) thermal desorption of deposits on the electrode surface and iii) limiting currents approximately an order of magnitude higher than those achieved by conventional isothermal heating to the same temperature.…”

Section: Non-isothermal Heating Methods: Microwave Heating Of Micro-ementioning

confidence: 99%

High‐Temperature Electrochemistry: A Review

et al. 2004

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High-temperature electrochemistry remains a relatively unexplored field of research, although in recent years significant developments have been made. This report details the main experimental methods and approaches to heating an electrochemical system under both isothermal and non-isothermal conditions and gives an insight into the experimental and electroanalytical results obtainable under such conditions. It has been shown that the promotion of mass transport at high-temperatures, through diffusion or convection, often results in increased current signals. This increase benefits electroanalytical measurements by lowering detection limits. High temperatures also usefully enhance the sensitivity of systems with sluggish kinetics.

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“…Dramatic effects are observed [7] and Faradaic current enhancements up to three orders of magnitude have been reported [8]. In subsequent studies, a simple physical model based on Joule heating and on a diffusion-convection mechanism have been suggested [9] and confirmed in organic solvent systems [10]. Most studies to date explored the microwave effects at platinum electrodes.…”

Section: Introductionmentioning

confidence: 98%

“…The microwave methodology employed here offers the benefit of being applied and controlled externally to a conventional electrode system with conventional electrochemical equipment. It has been shown that at metal electrodes self-focusing of the microwave radiation occurs [9] and a very high power density is available directly at the tip of the electrode immersed in the test solution. The solution phase is heated rather than the metal electrode and as a result, the highest temperatures are reached in the solution phase some 10 mm away from the electrode surface.…”

Section: Introductionmentioning

confidence: 99%

Microwave Activation of Electrochemical Processes at Glassy Carbon and Boron‐Doped Diamond Electrodes

et al. 2005

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Voltammetric experiments under intense microwave field conditions have been carried out at a carbon microfiber electrode, an array of carbon microfiber electrodes, and at a boron-doped diamond electrode. For the reversible one electron redox systems Fe(CN) 3À=4À 6 and Ru(NH 3 ) 3þ=2þ 6 in aqueous KCl solution increased currents (up to 16 fold at a 33 mm diameter carbon microelectrode) and superheating (up to ca. 400 K at all types of electrodes) are observed. Electrodes with smaller diameter allow better signal enhancements to be achieved. From the missing effect of the supporting electrolyte concentration on the microwave enhanced currents, it can be concluded that effects observed at carbon electrodes (microwave absorbers) are due to the interaction of microwaves with the electrode material whereas for metal electrodes (microwave conductors) effects are dominated by the interaction of the microwaves with the aqueous dielectric. Short heat pulses can be applied by pulsing the microwave field and relatively fast temperature transients are observed for small electrodes. For the irreversible two electron oxidation of l-dopa in aqueous phosphate buffer, different types of effects are observed at glassy carbon and at boron-doped diamond. Arrays of carbon microfibers give the most reproducible and analytically useful current signal enhancements in the presence of microwaves.

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Microwave activation of electrochemical processes: convection, thermal gradients and hot spot formation at the electrode∣solution interface

Cited by 54 publications

References 16 publications

Electroanalysis at Diamond‐Like and Doped‐Diamond Electrodes

Electroanalysis at Diamond‐Like and Doped‐Diamond Electrodes

High‐Temperature Electrochemistry: A Review

Microwave Activation of Electrochemical Processes at Glassy Carbon and Boron‐Doped Diamond Electrodes

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