Step 1: Definition of Standard Hydrogen Electrode (SHE).
The Standard Hydrogen Electrode (SHE) is a reference electrode used to measure the standard electrode potentials of other electrodes. Its standard electrode potential is defined as 0.00 V at all temperatures. It serves as the primary reference electrode in electrochemistry.
Step 2: Construction of SHE.
The Standard Hydrogen Electrode consists of:
• A platinum electrode (coated with platinum black to increase surface area).
• The electrode is dipped in a solution containing 1 M H+ ions (usually 1 M HCl).
• Pure hydrogen gas is bubbled over the platinum surface at a pressure of 1 atm.
• The temperature is maintained at 298 K (25°C) under standard conditions.
Step 3: Labeled Representation of SHE.
The symbolic representation of the Standard Hydrogen Electrode is:
Pt(s) | H2(g, 1 atm) | H+(aq, 1 M)
A simple labeled diagram description:
Hydrogen gas (1 atm) → bubbled over → Platinum electrode (Pt)
Platinum electrode immersed in → 1 M H+ solution
Step 4: Cell Reaction of SHE.
At the electrode surface, hydrogen gas and hydrogen ions are in equilibrium. The electrode reaction is:
H2(g) ⇌ 2H+(aq) + 2e−
• When acting as an anode:
H2(g) → 2H+(aq) + 2e−
• When acting as a cathode:
2H+(aq) + 2e− → H2(g)
Step 5: Importance of SHE.
The SHE is used to determine the standard electrode potential of other electrodes by coupling it with another half-cell. Since its potential is taken as zero, the measured cell potential directly gives the electrode potential of the other half-cell.
Conclusion.
Thus, the Standard Hydrogen Electrode is a fundamental reference electrode in electrochemistry, operating under standard conditions with a defined potential of 0.00 V and the reversible reaction between hydrogen gas and hydrogen ions.