KB-templated in situ synthesis of highly dispersed bimetallic NiFe phosphides as efficient oxygen evolution catalysts

Abstract

The oxygen evolution reaction (OER) plays a key role in sustainable energy technologies. Herein, we report a facile Ketjenblack carbon (KB)-templated in situ synthesis method to fabricate highly dispersed bimetallic NiFe phosphides as highly efficient OER electrocatalysts. The Fe dopant can effectively modulate the electronic structure and increase the oxidation degree of Ni₂P species. Remarkably, benefitting from the large specific surface area, optimized electronic structure and faster charge transfer kinetics, the KB-templated NiFe phosphides exhibit dramatically enhanced OER activity in alkaline medium. By tailoring the Ni/Fe ratio, (Ni_0.5Fe_0.5)₂P/C-KB-900 delivers a current density of 20 mA cm⁻² at an ultra-low overpotential of 296 mV and a small Tafel slope of 77 mV dec⁻¹, which is much more active than commercial RuO₂. Post-electrolysis characterization further reveals that the bimetallic phosphides are in situ converted to NiFe oxides/hydroxides during the OER, serving as the OER active sites with high activity. This work offers a novel route to design and fabricate transition metal phosphide/carbon catalysts for water splitting by controlling the morphology and composition.