NiFe and NiCo core-shell nanoparticles supported on graphene as efficient catalysts for oxygen evolution reaction

The development of inexpensive and abundant catalysts for water electrolysis is underway and a wide variety of transition metal-based carbon composites are being explored for the redox reactions involved in the electrochemical cycle of water, being Oxygen Evolution Reaction (OER) the bottleneck of this process. Herein, NiFe and NiCo core-shell nanoparticles supported on graphene 3D aerogels were developed for Oxygen Evolution Reaction. These hybrids were synthesised via freeze-casting method and thermal reduction, enabling an ultra-dispersion of the nanoparticles along the graphene oxide flakes, precise control over the nanoparticle size, and forming an active core-shell structure. The as-processed NiFe and NiCo core-shell nanoparticles consistently maintaining a low metal content of 10 wt% supported on graphene were successfully tested for OER and compared to the current state-of-the-art (NiFe Layered Double Hydroxides), obtaining overpotentials ranging from 400 to 450 mV at 10 mA cm⁻², a Tafel slope of 84.8 mV dec⁻¹ and great stability over 12 h.