Influence of a Magnetic Field on the Electrochemical Double Layer

Abstract

The electrode/electrolyte interface is the seat of electrochemical redox reactions, which are controlled by the structure of ions and solvent molecules at an interfacial double layer, 0.5−10 nm thick. Here, we show that a magnetic field can exert a large and unexpected influence on the double layera 0.5 T in-plane field modifies its capacitance and charge-transfer resistance by up to 50%. The effects are observed in nitrobenzene, a model electrochemical system, and they indicate a shift of the outer Helmholtz plane of up to 0.25 nm caused by Maxwell stress acting on the paramagnetic NB •− radicals in solution close to the electrode. There are prospects of using magnetic fields to explore the internal terra incognita lying a nanometer or so from the electrode surface and control critical interface phenomena involving nucleation or surface wetting.

Recent Advances in Magnetic Field-Enhanced Electrocatalysis

“…Recently, Dunne and Coey found an interesting phenomenon that Maxwell stress in the magnetic field can cause lateral or longitudinal stretching of the paramagnetic droplets and change the curvature and wettability of the paramagnetic ions in the diffuse double layer, leading to the location migration of OHP, thus affecting the electrochemical double layer. 74 Although there has not been any example using Maxwell stress to enhance the electrocatalytic performance, Maxwell stress was reported to the affect electrochemical double layer. Therefore, it is predicted that Maxwell stress may impact on electrochemical double-layer capacitance (EDLC, C dl ), which is an important evaluation parameter in the electrocatalytic reaction.…”

Electrochemistry in Magnetic Fields

“…c) Schematic of the distortion and capacitance decrease caused by the Maxwell stress. [68] Reproduced with permission. Copyright 2019 American Chemical Society.…”

“…Copyright 2020 American Chemical Society. c) Schematic of the distortion and capacitance decrease caused by the Maxwell stress [68] . Reproduced with permission.…”

“…Recent work by Dunne et al in 2019 described the importance of magnetoelectrochemistry and its effect on the electrochemical double layer. [68] They reported that the 0.5 T magnetic field could attract and distort the paramagnetic species on the electrode surface and contract the average outer Helmholz plane closer to the electrode by up to 0.25 nm as a result of the Maxwell stress. [68] The double-layer capacitance and charge-transfer resistance were also decreased simultaneously, as shown in Figure 15c.…”

Preparation of Co3O4 Electrodes with Different Morphologies for the Investigation of Magnetic Response in Hybrid Capacitors

“…Dunne et al . indicate a shift of the outer Helmholtz layer of up to 0.25 nm caused by Maxwell stress acting on the paramagnetic NB .− radicals in solution close to the electrode, which modifies its capacitance and charge‐transfer resistance by up to 50 % [7b] . Despite the significant efforts of these reported results, we note that the morphologies of the electrodes reported investigating the magnetic response are usually different, such as microtubular‐shape, [4a] fibre‐like, [9] leaflet‐shape, [10] etc ., which may affect the infiltration of the electrolyte and the interface channel of ions.…”