Enhanced Electrocatalytic Activity By External Magnetic Field for Oxygen Evolution Reaction
Authors: Aini Anafi , Ilhwan Oh 
Published: December 2020

Fossil fuel cannot be relied on anymore as an energy source. Oxygen and hydrogen from water electrolysis can be transformed into electrical energy by a fuel cell. In another way, oxygen and hydrogen can be produced by water splitting process using electrolyzer. There are two processes in water electrolysis, hydrogen evolution reaction (HER) that occur on the cathode and oxygen evolution reaction (OER) that occur on the anode. In this research, we will focus on oxygen evolution reaction.

Oxygen evolution is a process of generating oxygen molecules from water by oxidizing water during electrolysis process. To optimize the reaction, a catalyst is needed to be applied to the anode. Until now, some metal oxide such as iridium oxide and ruthenium oxide show the best performance as catalysts. However, they have limited costs. Effective and low-cost catalyst is the key to optimization process.

Oxygen has unpaired electrons, make it becomes paramagnetic. Magnetic field drives the direction of oxygen bubbles movement. Oxygen bubbles move towards S-pole and away from N-pole. In an electrolyzer system, the oxygen bubbles will move rotationally. This motion increases the electrolyte hydrodynamic, which serves as a stirrer. The hydrodynamic of electrolyte helps to detach oxygen bubbles in anode surface. Therefore, the internal resistance of the system decreases, and the electrocatalytic activity increases.

Moreover, during OER process, oxygen spins are randomly aligned. These randomly align spins lead over potential and inefficient oxygen production process. Magnetic field helps to polarized the oxygen spins. When the oxygen spins parallelly align, the oxidation reaction is improved. Current reports on magnetic effect during OER are still rare, therefore combining magnetic nanoparticle as catalyst and external magnetic force become very interesting.

Several magnetic materials such as ferrite nanoparticles and its substitutes (Mn, Co, Ni, Zn) are decorated on Ni foam as anode. Those catalysts then combined with the magnetic field by attaching a permanent neodymium magnet near the anode compartment. Pt mesh is employed as cathode and Hg/Hg2SO4 as reference electrode. Electrocatalytic activity is measured by cyclic voltammetry and chronoamperometry. OER process is done in alkaline liquid electrolyzer, and KOH is used as an electrolyte. This experiment will show the most suitable magnetic material combined with external magnet. Magnetic strength toward OER process also needs to be investigated. Further experiments will be conducted, such as detect and quantify the oxygen radical on the anode by Scanning Electrochemical Microscope (SECM), quantify the oxygen production by oxygen sensor, and detect the hydrogen peroxide formation.

Finally, the magnetic field from a permanent magnet has an essential role in electrocatalytic activity of magnetic material. With magnet exposure, the current density is higher rather than without magnet. This simple approach on OER has a significant impact on further applications such as solar fuel systems and fuel cells.