It is very hard to add something to Dr. Braun's answer...

I just want to note that normally, galvanostat using for battery testing (i.e. charge/discharge current is constant). As a result, you get the cell voltage dependence from the degree of charge or discharge. The geometric area of the electrode in the test cell should be used for current density calculation (current divided by area, this is most simple). The point is that the voltage and capacity of the cell or electrode in the process of charge/discharge depends on the current density (see Tafel equation in electrochemistry). Therefore, any charge/discharge curve for the test cell, electrode, etc. makes sense only if the current density is specified (sometimes in units of current per mass, C-units ...).

Hi,

The density of current is deduced from measured value of current intensity divided by the section area of wire in which there is a current circulation. But, there other methods which can be used for measuring current density.

With my best regards!

Dr. Adel OUESLATI

Hi Amrutha,

Current density is the measure of current generated per unit surface area of electrode.

Eg: In microbial fuel cell/fuel cells, if you are using electrode with size of 5cm x 2cm and current produced is 200mA, then current density will be,

CD= Current/(projected area of electrode)

area of rectangle= LxB= 5cm x 2cm =10cm2

CD= 200mA/10cm2

CD= 20mA/cm2

Your Current will be 200mA.

Current density will be 20mA/cm2.

NOTE: Area for 2D electrodes(square, rectangular, circular etc.) and Surface area for 3D electrodes (Cylindrical, rods, cuboid etc)

Dear Sir,

Current density is basically current per unit surface area of electrode.

Cd= 1mA/cm2

Bhim Thapa Your answer looks convincing, Thank you. However, I am wondering that if the dimension of the electrode is 5cm x 2cm , the projected area is 20 cm2 (if we neglect the thickness) isn't it ? If you can clarify this that would be really helpful.

I am running a microbial electrosynthesis reactor with carbon felt electrode, how can I calculate the surface area?

Hi Vasan,

Surface area for 3-dimesion electrode is calculated as LxBxH, whereas for 2-dimension electrode is LxB.

Thank you Bhim Thapa for the clarification. Could you please share any reference for this way of calculation (LxBxH) for 3D electrodes.

Hi..My working electrode is a 5 cm length fiber. How can I calculate the current density?.

If you are using electrode with size of 6cm x 2cm and current produced is 100mA, then current density will be,

CD= Current/(projected area of electrode)

area of rectangle= LxB= 6cm x 2cm =12cm2

CD= 100mA/12cm2

CD= 10mA/cm2

Your Current will be 100mA.

Current density will be 10mA/cm2.