Magnetic Field-Driven Dynamic Reorganization of Electrocatalytic Interfaces for Improved Oxygen Evolution

High Resolution Image Download MS PowerPoint Slide Nanofibers and nanorods of NiCo- and NiCoFe- oxides and phosphides were synthesized by hydrothermal methods, followed by phosphidation to yield (Ni,Co)P, (Ni,Co) 2 P, and FeP. The materials were evaluated as electrocatalysts for the oxygen evolution reaction (OER) in water splitting in the presence of a magnetic field in two electrolytes: 1 M KOH and 1 M phosphate buffer saline (PBS) solution. A standard electrochemical cell was equipped with disk magnets directed perpendicular to the electric field. The magnetic field affected the catalyst interface and increased the reaction rate. The best catalyst was found to be NiCoP, and the overpotential (at 10 mA/cm 2 ) was reduced from 330 to 260 mV when a magnetic field of 100 mT was applied and further to 170 mV when a magnetic field of 200 mT was applied. NiCoP has the highest proportion of magnetic domains aligned due to having the highest saturation magnetization (M s ), remanence magnetization (M r ), and the lowest coercivity (H c ). The mixed transition metal phosphide catalysts were found to partly transform into (Ni,Co) 3 (PO 4 ) 2 during electrocatalysis; however, they still responded to a change in the magnetic field. The results show that a weak magnetic field can improve the performance of electrocatalysts based on certain transition metals in a neutral pH electrolyte mimicking seawater.