limitations of standard hydrogen electrode

'SHE' stands for standard hydrogen electrode.

It is a platinum electrode dipped in 1 M solution of H+ ion (1 M HCl) at 298 K and hydrogen gas bubbled at 1 atm pressure. It acts as a reference electrode to find out the potential of the other half cell.

By convention it’s value is taken as zero. Emf of a cell is calculated by connecting the hydrogen electrode to any metal or non-metal electrode. After calculating Emf , one can easily calculate value using the formula Eo (cathode) –Eo(anode). As one of it is SHE, so by substituting its value i.e. zero, value of other electrode can be calculated.
Limitations of standard hydrogen electrode are :
1) It is very difficult to assemble the apparatus.
2) It is difficult to maintain the pressure of H2 gas of 1 atm throughout and also the concentration of H+ ion of 1 M.
3) H2 electrode cannot be used in presence of oxidising agent.
4) Impurities that are present in hydrogen flow may create the poison for platinum electrode and further which will alter the potential value.

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1) it's difficult to maintain the pressure of the hudrogen gas at 1 bar

2) it's difficult to maintain the 1 molar concentration of the [H+] ion

3) the Pt electrode used gets poisoned easily in the presence of even impurities
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