Suppressing Competing Solvent Reduction in CO Electroreduction with a Magnetic Field.

The presence of an external magnetic field is found to affect the competition between the HO and CO reduction reactions by increasing mass transport via the Lorentz force. Increasing the magnetic field strength at the electrode surface from 0 to 325 mT increases the selectivity of CO over H by 3×, while an increase in current density from 0.5 to 5 mA/cm increases the selectivity of CO production by 5×. Cyclic voltammetry and finite-element simulations reveal that the origin of the enhanced CO selectivity is attributable to a magnetic field lowering the electrode-electrolyte interfacial pH. A drop in interfacial pH enables increased production of CO from CO reduction due to a decrease in the activity of HO reduction and increase in CO solubility near the electrode surface. The insight provided in this study offers new opportunities to control reaction selectivity in electrocatalysis with magnetic field vectors.