The reference electrode defined as 0.00 V, with hydrogen gas at 1 bar over platinum in 1 M acid.
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The standard hydrogen electrode is the primary reference for electrode potentials and is assigned exactly 0.000 V under standard conditions. It consists of platinum coated with platinum black, immersed in a solution of hydrogen ions at unit activity, with hydrogen gas at 1 bar passing over the electrode. Because it is awkward to prepare and maintain, practical reference electrodes such as the calomel and silver-silver chloride electrodes are used in routine measurements. Their potentials are calibrated against the standard hydrogen electrode. All tabulated standard potentials are ultimately referred to it.
Key ideas: The SHE is a platinum electrode coated with platinum black in 1 M H+ with H2 gas bubbled at 1 bar, representing 2H+ + 2e- giving H2. It is assigned exactly 0.000 V at all temperatures as the universal reference. Practical references include saturated calomel (+0.241 V) and Ag/AgCl (about +0.197 V).
Common mistakes and connections: Mistakes: thinking 0 V means the SHE has no potential rather than being the arbitrary zero, and forgetting that true unit activity corresponds to roughly 1.18 M HCl rather than 1 M. The SHE is awkward to use, so secondary electrodes are corrected back to the SHE scale.
The standard hydrogen electrode, H2 gas at 1 bar over platinum in 1 M H+, defines 0.000 V, the reference for all tabulated potentials. The interactive lesson shows this as a live animation or chart.
A copper half-cell measured against the standard hydrogen electrode gives a reported potential of +0.34 V for the Cu2+/Cu couple.
The reference electrode defined as 0.00 V, with hydrogen gas at 1 bar over platinum in 1 M acid.
Standard Hydrogen Electrode is a intermediate topic in Acids, Bases & Electrochemistry. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Acids, Bases & Electrochemistry first: Salt Bridge, Cell Notation, Standard Electrode Potential.
The next topics in Acids, Bases & Electrochemistry are Cell Potential and Electrochemical Series.
Yes. The interactive lesson includes a self-check question on Standard Hydrogen Electrode, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Standard Hydrogen Electrode is topic 51 of 105 in Acids, Bases & Electrochemistry.