Mohit Saraf

In short, surface area provides sites for formation of electrical double layers, and hence improves the capacitance by increasing the area of the electrical double layers. The porosity plays a similar role, but it could also affect ion diffusion kinetics depending on the pore inter-connectiveness, which determines the rate capability performance.

I have a paper that elaborate my answer, please check it out if you are interested:

Article Revitalizing Carbon Supercapacitor Electrodes with Hierarchi...

(This is a pre-print copy. Please directly message me if you want a formatted, published PDF copy.)

The primary reason increasing the surface area affects capacitance can be understood from the equation for a parallel plate capacitor: C = k*e0*A/d where C is the capacitance, k is the relative permeability, e0 is the permeability of free space, A is the surface area of the plate, and d is the distance between the plates. Therefore, increasing the surface area via the introduction of pores into the material increases the capacitance of the device. A larger capacitance is ideal for sensors which use variations in the capacitive response as a means of sensing an analyte.

Mohit Saraf

In short, surface area provides sites for formation of electrical double layers, and hence improves the capacitance by increasing the area of the electrical double layers. The porosity plays a similar role, but it could also affect ion diffusion kinetics depending on the pore inter-connectiveness, which determines the rate capability performance.

I have a paper that elaborate my answer, please check it out if you are interested:

Article Revitalizing Carbon Supercapacitor Electrodes with Hierarchi...

(This is a pre-print copy. Please directly message me if you want a formatted, published PDF copy.)

A Higher porosity will produce larger surface areas, which affords one of the important characteristics for high-performance SCs. Hence, it logically to deem that the porous material with high surface areas will produce additional active sites for adsorption-desorption process and ion-electron transport in SCs.

A poros material prepares more area for double layer. For instance if you use a supercapacitor cell which consists of two electrodes by a porous material as electrode the electrolyte has more area to flow through the main poros material. So you will have higher capacitance and it can be understood from the results that you obtain from Cyclic voltammetry and galvanostatic charge-discharge analysis. If you need a reference book about fundamentals of charge-discharge mechanism in double layer supercapacitors you may use this book if you are interested:

Electrochemical Supercapacitors

Scientific Fundamentals and Technological Applications

Authors: Conway, B. E.

Dear Mohit Saraf ,

start recalling in your memory the figure-model of a vacuum variable capacitor[1]; then, start shrinking this electronic capacitor (say 1cm) size towards nanosize range. Now, add N (number of these) nanosize capacitors, in (quasi-)parallel[2] connection, till initial common size (say 1cm), again.

The electrolyte in real Electrochemical Supercapacitors has an additional (hidden) role; it helps to form a virtual ionic quasi-plate (in the electrolyte, e.g. the ionic side of the quasi-)parallel[2] connection.

So, the surface area might provide some additional sites for conventional electrochemical capacitors' case, but Electrochemical Supercapacitors add much more (huge, quantum[3]) capacitance due to nano-plates' (quasi-)parallel position[4] in space, an induced plate chirality effect, (like actions in variable capacitor[1]), e.g. not only, due to the high(er) surface.

This process for nano-plates' (quasi-)parallel position belongs in the conventional context of the (electrode) material's activation processes[6].

1. https://en.wikipedia.org/wiki/Vacuum_variable_capacitor

2. One of the two plates is in the same Voltage but the other plate is mnot the same case; it is in the (quasi-)same electrochemical Potential.

3. https://en.wikipedia.org/wiki/Quantum_capacitance

4. It is like a Maxwell demon(1867)[4], not for velocity, but for parallel position activation process.

5. https://en.wikipedia.org/wiki/Maxwell%27s_demon

6. https://www.researchgate.net/post/In_Supercapacitors_For_a_metal_oxide_electrode_What_is_the_best_way_to_do_an_electrochemical_activation_before_the_measurements#view=5d4d21e5aa1f096dea47295d