How does pH affect electrode potential in electrochemical cells?

The relationship between pH and electrode potential in electrochemical cells is closely tied to the concentration of hydrogen ions (H⁺) in the solution. According to the Nernst equation, which describes how the potential of an electrode is affected by the concentration of ionic species, the electrode potential is influenced by the activity—or concentration—of hydrogen ions.

In acidic conditions (lower pH), there is a higher concentration of hydrogen ions, which can increase the potential of certain half-reactions, such as those involving the reduction of hydrogen ions to hydrogen gas. Conversely, in basic conditions (higher pH), the concentration of hydrogen ions is lower, which can decrease the electrode potential.

Therefore, pH serves as a critical factor in modifying the concentration of hydrogen ions, directly impacting the electrode potential and, consequently, the overall behavior of the electrochemical cell. This impact is crucial in many applications, including batteries and fuel cells, where changes in pH can lead to significant variations in performance and efficiency.