The platinum electrode in the Standard Hydrogen Electrode (SHE) plays a crucial role in facilitating the redox reactions involving hydrogen gas and hydrogen ions.
This electrode is essential for establishing a reference potential for measuring the electrode potentials of other electrochemical systems.
Here, we will delve into the detailed function of the platinum electrode in the SHE, its construction, and its significance in electrochemical measurements.
5 Key Points Explained: The Role and Function of Platinum in SHE
1. Role of Platinum in SHE
Platinum acts as a catalyst for the oxidation and reduction reactions of hydrogen.
It facilitates the transfer of electrons between hydrogen gas (H2) and hydrogen ions (H+) in the solution.
Platinum is chosen due to its inertness, meaning it does not react with hydrogen or other components in the solution, ensuring that it does not interfere with the electrode reactions.
2. Construction of SHE
The SHE consists of a platinized platinum foil or plate, which is connected to a platinum wire.
This setup allows for the exchange of electrons.
Pure and dry hydrogen gas is bubbled through the solution at a constant pressure of 1 atm.
The hydrogen gas is adsorbed onto the platinum surface, creating a hydrogen electrode.
A small amount of mercury is present at the bottom of the glass tube to ensure good electrical contact.
3. Electrode Reaction
The electrode reaction in SHE is reversible with respect to hydrogen ions.
The reaction can be represented as: [ 2H^+(aq) + 2e^- \rightleftharpoons H_2(g) ]
During the reaction, hydrogen gas from the platinum plate converts into hydrogen ions, releasing electrons.
These electrons accumulate on the platinum plate, creating a potential difference.
4. Significance of SHE
The SHE is used as a universal reference electrode in electrochemistry.
Its standard electrode potential is arbitrarily set to zero, which forms the basis for calculating the potentials of other electrodes.
By coupling SHE with another electrode, the potential of the cell can be measured using a potentiometer.
Since the potential of SHE is zero, the measured potential directly represents the potential of the other electrode.
5. Advantages and Challenges
Advantages
SHE can be used over the entire pH range.
It does not introduce any salt error in measurements.
Provides a consistent and reliable reference for electrochemical measurements.
Challenges
Difficult to obtain 100% pure and dry hydrogen gas.
Maintaining exactly 1 atm pressure and 1 M HCl concentration is challenging.
The glass construction makes it fragile and less portable.
6. Practical Considerations
Due to the practical difficulties in setting up and maintaining an SHE, it is often referred to as a hypothetical electrode.
Other standard electrodes like the Calomel electrode are often preferred due to their ease of use and stability.
In summary, the platinum electrode in the SHE is pivotal for catalyzing the redox reactions of hydrogen, ensuring a stable and consistent reference potential for electrochemical measurements.
Despite the challenges in its setup and maintenance, the SHE remains a fundamental tool in the field of electrochemistry.
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