Standard Hydrogen Electrode: Working, Uses

Standard Hydrogen Electrode: A Standard Hydrogen Electrode or SHE is an electrode that all the research scientists use for half-cell electrode reactions. The ultimate value of standard electrode potential is zero. Standard Hydrogen Electrode contains both the positive and negative electrode potentials. Determination is done using reference electrodes such as standard hydrogen electrodes, calomel electrodes, and so on. As a result, in an electrochemical process, SHE serves as both a cathode and an anode. If you want to specialize in chemical engineering, you must be well-versed in this topic.

This article will discuss the important applications of SHE in the everyday life of humans. Keep on scrolling through this article in order to know more about the application of the standard electrode potential of hydrogen, the standard hydrogen electrode diagram, and more.

What is Standard Hydrogen Electrode Potential?

The electrical difference set up between the metal and its ion in the solution is called electrode potential. It is also defined as the tendency of an electrode to lose or gain electrons when in contact with its ion solution. The electrode potential is also termed oxidation potential if the oxidation occurs at the electrode concerning the reference electrode. It is called reduction potentials if the reduction occurs at the electrode concerning the reference electrode like a standard hydrogen electrode.

In the half cell, the metal electrode is suspended in a solution of one molar concentration at \(298\;{\rm{K}}\), and the electrode potential is called standard electrode potential. It is represented by the symbol \({{\rm{E}}^{\rm{o}}}.\)

Explain Standard Hydrogen Electrode

The standard hydrogen electrode is set up by passing pure hydrogen gas at one atmospheric pressure in a solution of \({{\rm{H}}^ + }\) ions of concentration of \(1\,{\rm{mol/L}}\) in contact with a platinised platinum foil.

The standard hydrogen electrode is represented as \(\left. {{\rm{Pt}},\,{{\rm{H}}_{\rm{2}}}\left( {\rm{g}} \right)\left( {{\rm{1}}{\mkern 1mu} {\rm{atm}}} \right)} \right|\,{{\rm{H}}^{\rm{ + }}}\left( {{\rm{1mol/L}}} \right)\)

Working of Standard Hydrogen Electrode

Standard Hydrogen Electrode can work both as an anode and as a cathode.

When a standard hydrogen electrode undergoes oxidation in a cell, it acts as an anode. During this process, hydrogen gets changed into \({{\rm{H}}^ + }\) ions which go into the solution.

\({{\rm{H}}_2} \to 2{{\rm{H}}^ + } + 2{{\rm{e}}^ – }\)

When a standard hydrogen electrode undergoes a reduction in a cell, it acts as a cathode. During this process, \({{\rm{H}}^ + }\) ions from the solution change into hydrogen gas.

\(2{{\rm{H}}^ + } + 2{{\rm{e}}^ – } \to {{\rm{H}}_2}\)

Thus, the electrode is reversible concerning \({{\rm{H}}^ + }\) ions.

The electrode potential of the standard hydrogen electrode is zero at \({\rm{298}}\,{\rm{K}}\).

Measurement of Electrode Potential

To determine an electrode’s potential, a cell is set up using the electrode as one of the electrodes and the second electrode as the standard hydrogen electrode. The emf of the cell is then measured. The emf of the cell is the sum of the oxidation potential and reduction potential of the cell.

One of the electrodes involved in the standard hydrogen electrode has an electrode potential that is zero; therefore, the emf of the cell will be directly given the electrode potential of the electrode under investigation. The direction of the current flow indicates whether the oxidation takes place or reduction takes place on the electrode under the investigation concerning the hydrogen electrode. According to this, the electrode potential is termed oxidation potential or reduction potential.

Let us understand the concept using the Standard Hydrogen Electrode Diagram given below.

Advantages of Standard Hydrogen Electrode

1. It can be used for a range of \({\rm{pH}}\) values.
2. The standard hydrogen electrode potential is zero. Therefore, the electrode potential of another electrode can be easily calculated.

Disadvantages of Standard Hydrogen Electrode

1. Platinum is expensive, and platinised platinum is difficult to prepare.
2. Maintaining the pressure of hydrogen and the concentration of acid is not easy.
3. It isn’t easy to obtain pure hydrogen.

Solved Examples on Application of Standard Hydrogen Electrode

Calculate the emf of the cell at \({\rm{2}}{{\rm{5}}^{\rm{o}}}{\rm{C,}}{\mkern 1mu} \,{\rm{Fe}}\left| {\left. {{\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}{\rm{(0}}{\rm{.001}}\,{\rm{M)}}} \right\|{{\rm{H}}^{\rm{ + }}}{\rm{(1}}{\rm{.0}}\,{\rm{M)I}}{{\rm{H}}_{\rm{2}}}{\rm{(1}}\,{\rm{atm)}}} \right|\,{\rm{Pt}}{\rm{.}}\) Given: \({\rm{E}}_{{\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}{\rm{/Fe}}}^{\rm{o}}{\rm{ = – 0}}{\rm{.44}}\,{\rm{V}}\)

At the anode, \({\rm{Fe(s)}} \to {\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}{\rm{ + 2}}{{\rm{e}}^{\rm{ – }}}\)

At the cathode, \(2{{\rm{H}}^ + } + 2{{\rm{e}}^ – } \to {{\rm{H}}_2}\)

Net reaction, \({\rm{Fe}}\left( {\rm{s}} \right){\rm{ + 2}}{{\rm{H}}^{\rm{ + }}} \to {\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}{\rm{ + }}{{\rm{H}}_{\rm{2}}}\)

The emf at \({25^{\rm{o}}}{\rm{C}}\) is given by,

\({{\rm{E}}_{{\rm{cell}}}}{\rm{ = \;E}}_{{\rm{cell}}}^{\rm{^\circ }}{\rm{ – }}\frac{{{\rm{0}}{\rm{.0591}}}}{{\rm{2}}}{\rm{\;log\;}}\frac{{\left[ {{\rm{F}}{{\rm{e}}^{{\rm{2 + }}}}} \right]}}{{{{\left[ {{{\rm{H}}^{\rm{ + }}}} \right]}^{\rm{2}}}}}\)

\({{\rm{E}}_{{\rm{cell}}}}{\rm{ = }}\left( {{\rm{0 – EF}}{{\rm{e}}^{{\rm{2 + }}}}{\rm{/F}}{{\rm{e}}^{\rm{o}}}} \right){\rm{ – }}\frac{{{\rm{0}}.{\rm{0591}}}}{{\rm{2}}}{\rm{log}}\frac{{{\rm{0}}.{\rm{001}}}}{{{{\left( {{\rm{1}}.{\rm{0}}} \right)}^{\rm{2}}}}}\)

\({{\rm{E}}_{{\rm{cell}}}} = \left[ {0 – \left( { – 0.44} \right)} \right] – \frac{{0.0591}}{2}\log {10^{ – 3}}\)

\({{\rm{E}}_{{\rm{cell}}}} = \left[ {0 – \left( { – 0.44} \right)} \right] – \frac{{0.0591}}{2}\log {10^{ – 3}}\)

\({{\rm{E}}_{{\rm{cell}}}} = 0.44 – \frac{{0.0591}}{2} \times – 3\)

\({{\rm{E}}_{{\rm{cell}}}} = 0.44 + 0.09\)

\({{\rm{E}}_{{\rm{cell}}}} = 0.53\;{\rm{V}}\)

Summary

In this article, we discussed the standard hydrogen electrode, its setup, working, advantages, and disadvantages in a simple and easy method. We also explained the standard hydrogen electrode conditions. Know that the Standard Hydrogen Electrode SHE is the basic guide for the reporting of the capacity of quantitative half-cells. Also, it should be known that SHE is an electrode that scientists use for reference on all half-cell potential reactions.

FAQs on Standard Hydrogen Electrode

Q.1. What is the use of standard hydrogen electrodes?
Ans: The electrode potential of the standard hydrogen electrode is zero. Therefore, the electrode potential of another electrode can be easily calculated. 

Q.2. What are the features of a standard hydrogen electrode?
Ans: Standard hydrogen electrode is set up by passing pure hydrogen gas at one atmospheric pressure in a solution of \({{\rm{H}}^ + }\) ions of concentration of \({\rm{1}}\,{\rm{mol/L}}\) in contact with a platinized platinum foil.

Q.3. What is the disadvantage of hydrogen electrodes?
Ans: The disadvantages of hydrogen electrodes are platinum is expensive, and platinised platinum is difficult to prepare. Maintaining the pressure of hydrogen and acid concentration is not easy, and pure hydrogen is difficult to obtain. 

Q.4. Why is hydrogen used as a standard electrode?
Ans: Hydrogen electrodes can work both as anode and cathode by undergoing oxidation and reduction, respectively. The hydrogen electrode is reversible concerning \({{\rm{H}}^ + }\) ions. The electrode potential of the standard hydrogen electrode is zero at \({\rm{298}}\,{\rm{K}}.\) Therefore, hydrogen is used as a standard electrode.

Q.5. What is a standard hydrogen electrode? How is it prepared?
Ans: A standard hydrogen electrode is a reference electrode used to determine the electrode potential of a cell.
Standard hydrogen electrode is set up by passing pure hydrogen gas at one atmospheric pressure in a solution of \({{\rm{H}}^ + }\) ions of concentration of \({\rm{1}}\,{\rm{mol/L}}\) in contact with a platinized foil.