What is the diffusion layer thickness?
The definition of the thickness of the diffusion layer is arbitrary because the concentration approaches asymptotically the value in the bulk solution”. At slow scan rates, the diffusion layer is large, on the order of micrometers, whereas at fast scan rates the diffusion layer is nanometers in thickness.
What is diffuse layer definition?
Definition. Diffuse double layer (DDL) is an ionic structure that describes the variation of electric potential near a charged surface, such as clay, and behaves as a capacitor. This ionic structure consisting of the negative surface charges, adsorbed cations, and diffuse layer is known as the diffuse double layer, DDL …
How do you determine the thickness of the diffusion layer?
The linear diffusion layer thickness is given by the value on the abscissa axis (x-axis) at which the linear concentration profile takes the value unity, corresponding to the bulk of the solution. The real diffusion layer thickness is given by the abscissa of the concentration profile corresponding to a value .
What is nernst diffusion layer?
Nernst diffusion layer is a virtual layer, within which the gradient of the ion concentration is constant and equal to the true gradient at the electrode-electrolyte interface. The thickness of the Nernst diffusion layer may be measured on the graph “ion concentration vs. distance from the electrode surface”.
What is the meaning of diffusion in bio?
Diffusion is the net passive movement of molecules or particles from regions of higher to regions of lower concentration. Thus, diffusion is characterized by a net movement of the particle down their concentration gradient — or in other words, from the area of greater concentration to an area of lower concentration.
Where and how diffuse layer is formed?
Diffuse-double-layer theory states that as colloidal particles assume a positive or negative charge due to the presence of charged groups within, or adsorption of a charged layer from, the surrounding medium, an electrical double layer of the opposite charge is formed at the interface between the solid phase and the …
What are the factors affecting the diffused double layer thickness?
The thickness of the diffuse double layer depends upon the following factors:
- (i) Concentration of Total Electrolyte: With an increase in total electrolyte concentration, the thickness of the diffuse double layer decreases.
- (ii) Valence of the Counter Ion:
- (iii) Dielectric Constant:
What is diffusion boundary?
The diffusion boundary is a very thin layer of fluid at the edge of the fluid where diffusion takes place between two systems. It permits diffusion of certain substances but may block diffusion of certain chemicals across it. It is is just some internal area within a volume of the diffusing material.
What is the thickness of the diffusion layer?
A fictitious layer corresponding to the dotted straight lines of the diagram which shows the concentration profile along the direction perpendicular to an electrode surface. The thickness δ of this layer is called the effective (or equivalent) thickness of the
What makes the MPL different from the diffusion layer?
The MPL is made of carbon black and PTFE binder. It has much smaller pores (20–200 nm) than the diffusion layer. MPL is characterized by its thickness, type of carbon particle, carbon loading, and PTFE content.
How big is the diffusion layer at slow scan rates?
At slow scan rates, the diffusion layer is large, on the order of micrometers, whereas at fast scan rates the diffusion layer is nanometers in thickness. The relationship is described in part by the Cottrell equation.
What makes up the diffusion layer of a cathode?
Typically, the diffusion layer at both the anode and cathode consists of two layers: a backing layer, which is made of carbon cloth or carbon paper, and a microporous layer (MPL), which is composed of hydrophobic polymer such as polytetrafluoroethylene (PTFE) and carbon powder (e.g., Vulcan XC-72).