spontaneity of galvanic cell

Unlike the change in Gibbs free energy for chemical reactions, a galvanic cell is spontaneous (product-favored) when the standard cell potential is positive (${\xi }^{\circ }>0$). Likewise, the cell is in equilibrium when ${\xi }^{\circ }=0$. Nonspontaneous (reactant-favored) when ${\xi }^{\circ }<0$, resulting in electrolysis.