In-situ synthesis of bimetallic phosphide with carbon tubes as an active electrocatalyst for oxygen evolution reaction

Abstract

Transition metal phosphides (TMPs) are attracting increasing interest as promising electrocatalysts for the oxygen evolution reaction (OER). Coupling TMPs with carbon materials can increase OER activity by improving the dispersion of active sites and introducing more OER-active species. However, the overwhelming majority of previous works have used either ex-situ methods to prepare TMPs@carbon hybrids or have obtained TMPs@ disordered carbons. Here, we report an in-situ synthesized TMPs coupled with carbon tubes as an active OER catalyst. Bimetallic NiFe phosphide (Ni2-xFexP) coupled with N/P co-doped carbon tubes (NPC), i.e., Ni2-xFexP@NPC, is prepared by pyrolyzing phytic acid sodium salt hydrate, melamine, and transition metal nitrate. Bimetallic NiFeP@NPC is found more active in catalyzing OER compared to monometallic Ni2P@NPC and Fe2P@NPC, metal-free NPC, and NiFeP@P-doped disordered carbon (NiFeP@PC). Its high performance is attributed to the unique tubular structure of its carbon material and the addition of a second metal into binary TMPs, contributing to a larger electrochemical active surface area and faster charge transfer kinetics. Moreover, NiFeP@NPC exceeds the benchmark RuO2 in terms of the OER activity, and it exhibits little activity degradation in both accelerated aging and chronopotentiometric tests, demonstrating a great promise as a high-performance OER electrocatalyst.