Crystalline/amorphous composite interface induced by NaBH4 hydrolysis reaction: a new interfacial electrocatalyst for efficient oxygen evolution reaction

Amorphous/crystalline composites are candidates for achieving high-performance oxygen evolution reaction (OER) catalysts by combining the two key factors of abundant catalytic sites and good electrical conductivity. Herein, an efficient OER catalyst with the solid solution of amorphous Ni2P and Fe2P nanosheets decorated with crystalline Fe3P0·37B0.63 alloy nanoparticles (FePB/NiFeP) is prepared successfully. This amorphous/crystalline composite is synthesized through a simple NaBH4 hydrolysis reaction followed by a high-temperature phosphating process. After hydrolysis of NaBH4, boron is adsorbed on NiFe2O4 precursors in the form of BO2−, and their presence promotes the formation of crystalline FePB alloy nanoparticles and amorphous Ni2P and Fe2P solid solutions. The activated FePB/NiFeP exhibits excellent stability and a superb OER activity of 10 mA cm2 with an overpotential of only 182 mV and a Tafel slope of 43.9 mV/dec, which is superior to most reported transition metal-based OER electrocatalysts. This study provides an idea for the rational design of other advanced amorphous/crystalline interfacial electrocatalysts.