Magnetic field induced micro-convective phenomena inside the diffusion layer during the electrodeposition of Co, Ni and Cu

Enhancing Electrochemical Reactivity with Magnetic Fields: Unraveling the Role of Magneto-Electrochemistry

Electrocatalysis performs a vital role in numerous energy transformation and repository mechanics, including power cells, Electric field-assisted catalysis, and batteries. It is crucial to investigate new methods to improve electrocatalytic performance if effective and long-lasting power systems are developed. The modulation of catalytic activity and selectivity by external magnetic fields over electrochemical processes has received a lot of interest lately. How the use of various magnetic fields in electrocatalysis has great promise for building effective and selective catalysts, opening the door for the advancement of sophisticated energy conversion is discussed. Furthermore, the challenges and possibilities of incorporating magnetic fields into electrocatalytic systems and suggestions for future research areas are discussed.

Magnetic Field-Assisted Construction and Enhancement of Electrocatalysts

Driven by the energy crisis and environmental pollution, developing sustainable clean energy is an effective strategy to realize carbon neutrality. Electrocatalytic reactions are crucial to sustainable energy conversion and storage technologies, and advanced electrocatalysts are required to improve the sluggish electrocatalytic reactions. The magnetic field, as a thermodynamic parameter independent of temperature and pressure, is vital in the construction of electrocatalysts and enhancement of electrocatalysis. In this Review, the recent progress of magnetic field-assisted construction of electrocatalysts and enhancement of electrocatalysis is comprehensively summarized. Originating from the structure-activity-performance relationship of electrocatalysts, the fundamentals of the magnetic field-induced construction of electrocatalysts, including the magnetocaloric effect, nucleation and growth, and phase regulation, have been illustrated. In addition, the magnetic effect on the electrocatalytic reaction, namely, the magnetothermal, magnetohydrodynamic and micro magnetohydrodynamic, Maxwell stress, Kelvin force, and spin selection effects, are discussed. Finally, the perspective and challenges for magnetic field-assisted construction of electrocatalysts and enhancement of electrocatalysis are proposed.

Magneto-Revealing and Acceleration of Hidden Kirkendall Effect in Galvanic Replacement Reaction

Rate and product control are crucial for a chemical process and are useful in a wide range of applications. Traditionally, thermodynamic parameters, such as temperature or pressure, have been used to control the chemical reactions. Here, by using the fabrication of a hollow Mn_xFe_yO₄ nanostructure as a model system, we report an experimental tuning of both chemical reaction rate and product by a high magnetic field. A 12 times magneto-acceleration of the galvanic replacement (GR) reaction was observed. Moreover, it is first demonstrated that a magnetic field can unravel and accelerate the hidden Kirkendall effect (KE) in addition to the pristine GR reaction. With coaction of magneto-tuned KE and GR, not only the rate but also the composition as well as magnetic property of the products could be modulated. These observations suggest that not only is a magnetic field a variable parameter that cannot be ignored, but also it can effectively control both rate and product in a chemical reaction, which provides a new route for chemical process controlling and shape/composition designing in material synthesis.

Magnetothermal Convection of Water with the Presence or Absence of a Magnetic Force Acting on the Susceptibility Gradient

Heat transfer of magnetothermal convection with the presence or absence of the magnetic force acting on the susceptibility gradient (f_sc) was examined by three-dimensional numerical computations. Thermal convection of water enclosed in a shallow cylindrical vessel (diameter over vessel height = 6.0) with the Rayleigh-Benard model was adopted as the model, under the conditions of Prandtl number 6.0 and Ra number 7000, respectively. The momentum equations of convection were nondimensionalized, which involved the term of f_sc and the term of magnetic force acting on the magnetic field gradient (f_b). All the computations resulted in axisymmetric steady rolls. The values of the averaged Nu, the averaged velocity components U, V, and W, and the isothermal distributions and flow patterns were almost completely the same, regardless of the presence or absence of the term of f_sc. As a result, we found that the effect of f_sc was extremely small, although much previous research emphasized the effect with paramagnetic solutions under an unsteady state. The magnitude of f_sc depends not only on magnetic conditions (magnitudes of magnetic susceptibility and magnetic flux density), but also on the thermal properties of the solution (thermal conductivity, thermal diffusivity, and viscosity). Therefore the effect of f_b becomes dominant on the magnetothermal convection. Active control over the density gradient with temperature will be required to advance heat transfer with the effect of f_sc.

Effect of a gradient static magnetic field on an unstirred Belousov-Zhabotinsky reaction by changing the thickness of the medium

The anomalous chemical wave propagation of an unstirred Belousov-Zhabotinsky (BZ) reaction was observed under exposure to a gradient static magnetic field (SMF). The gradient SMF effect on the BZ reaction was investigated by increasing the thickness of the BZ medium up to 0.9 mm under the conditions of the extremely reduced water evaporation and surface tension caused by air-water interfaces. The respective maximum values of magnetic flux density (B(max)), magnetic flux gradient (G(max)), and the magnetic force product of the magnetic flux density x its gradient (a magnetic force parameter) are 0.206 T, 37 T m(-1), and 4 T(2) m(-1). The experiments demonstrate that the more increased thickness of the BZ medium induces the larger anomalous wave propagation toward the peak magnetic gradient line but not toward the peak magnetic force product line. The anomalies were significantly enhanced by the increased thickness of the BZ medium at the shorter distance from the maximum magnetic gradient point. The possible mechanism of SMF-induced anomalous wave propagation related to the BZ medium thickness is that the micro-magneto-convection-induced flow of the paramagnetic iron ion complexes at the wavefronts can be accelerated by increases in both the spatial magnetic gradient and the volumetric depth of the diffusion layer.