Short note on Hydrogen Electrode.

Hydrogen electrode: -

The standard hydrogen half cell or Standard hydrogen electrode ( SHE ) is used for coupling with unknown half cell. It consists of a platinum electrode immersed in a 1M solution of H+ ions maintained at 25-degree centigrade. Hydrogen gas at one atmosphere enters into glass hood and bubbles over the platinum electrode. The hydrogen pass into the solution forming h+ ions and electrons liberated in the solution.

                                              H₂                       2H⁺+2e^-

The half cell whose potential is desired is combined with the hydrogen electrode and the emf of the complete cell determined with a voltmeter. The emf of the cell is the emf of half cell.

                          E⁰_cell = E⁰_R-E⁰_L

                                                   ₌ 0-0.76   = -0.76V