NiFe2O4 hollow nanoparticles of small sizes on carbon nanotubes for oxygen evolution

The efficiency of electrochemical hydrogen production is limited by the sluggish oxygen evolution reaction (OER) occurring at the anode. Herein, CNT-supported Ni–Fe bimetallic oxide hollow nanoparticles (NiFe2O4-HNP/CNTs) based on the Kirkendall effect were fabricated via a facile method. These NiFe2O4 hollow nanoparticles were uniformly distributed on the outmost surfaces of the CNTs with an ultra-small size of about 10 nm in diameter and 3 nm in wall thickness, which provide a significantly increased number of active sites and reduced charge transfer resistance for OER. As a result, the as-synthesized NiFe2O4-HNP/CNTs exhibit excellent OER performance with a current density of 10 mA cm−2 at a low overpotential of 260 mV and a small Tafel slope of 40 mV dec−1 as well as robust stability, superior to the benchmark IrO2 catalyst. Our results demonstrate that constructing hollow nanostructures with a small size on the conductive substrate is an efficient strategy for highly efficient oxygen evolution.