The spin state of the metal in electrocatalysts influences the catalytical properties of the catalysts, in terms of its efficiency and selectivity. Previous studies have concluded that the spin state affects both the thermodynamic interaction between the catalyst and the reaction intermediate and the kinetics of electron transfer. Based on this foundation, catalysts can be designed to lead the electrocatalytic reactions into a more efficient and selective pathway. With the assistance of external magnetic field, this optimization can be further amplified.