concentration cell

A concentration is a galvanic cell with two cells having the identical electrodes but differing concentrations. The concentration cell is able to generate electricity as the two sides try to reach an concentration middle-ground.

The cathode of a concentration cell is the half-cell that has the higher concentration, since in order to lower the concentration (and balance it with the other cell), ions have to be reduced.

According to the Nernst equation, the cell potential of a concentration cell is as below. Note that the $E^{\circ }$ term is gone since both half-cells has the same half-reaction but reversed, which cancels each other out.

$$\begin{array}{rl}\xi & =-\frac{RT}{nF}\ln Q\\ & =-\frac{0.0257}{n}\ln Q\end{array}$$