Enhanced bifunctional water electrolysis performance of spherical ZnMn2O4 nanoparticles

Abstract

Spinel-type transition metal oxide-based catalysts are crucial for efficient electrocatalytic oxygen and hydrogen generation. Therefore, in this study, zinc manganite (ZnMn2O4) nanostructures were synthesized using two different reducing agents, including sodium carbonate (Na2CO3) and sodium hydroxide (NaOH), through the coprecipitation method. When ZnMn2O4 was synthesized using NaOH, the sample exhibited a morphology with the aggregated and stacked nanobundles. In contrast, the Na2CO3-derived ZnMn2O4 sample demonstrated an interconnected and agglomerated spherical nanoparticle structure. For the oxygen evolution reaction, the spherical ZnMn2O4 nanoparticles exhibited the exceptional electrocatalytic performances, with an overpotential of 110 mV and a low Tafel slope of 47 mV/dec, showing excellent durability at 10 mA/cm2 in an alkaline electrolyte. For the hydrogen evolution reaction, the spherical ZnMn2O4 nanoparticles indicated a low overpotential of 158 mV and a Tafel slope of 120 mV/dec, with excellent stability at −10 mA/cm2. These findings suggest that the spherical ZnMn2O4 nanoparticles are effective electrocatalysts for highly efficient water-splitting. © 2024 Hydrogen Energy Publications LLC