P, N-codoped carbon nanofibers confined ultra-small bimetallic NiCoP for highly efficient overall water splitting

Abstract

Integrating the unique metalloid behaviour of monometallic phosphides and modified local electronic/geometric structures of active sites, bimetallic phosphides have emerged as promising candidates for water splitting reaction, but they are still synthesized by toxic, corrosive, and high-temperature methods, which inevitably resulted in an increase of particle size and the decrease of catalytic activity area. Herein, the ultra-fine bimetallic NiCoP catalysts in-situ embedded in P, N-codoped carbon nanofibers (NiCoP@PNCNF) were successfully fabricated via a facile electrospinning method with the help of phytic acid. Profiting from the unique macro-structural design and micro-electronic/geometric modification, as-prepared NiCoP@PNCNF catalysts exhibited excellent catalytic performance both for HER (η10 = 98 mV) and OER (η10 = 260 mV) in terms of the low overpotential and robust stabilities in alkaline solution. Meanwhile, XAFS analysis further demonstrated that the remarkable catalytic performance not only attributed to the introduction of heteroatom-doped carbon fibers as their improvements in the corrosion resistance, anti-agglomeration abilities, and conductivity, but also benefited from the local electronic/geometric structure alternations as the strong synergic effects between Ni/Co and P atoms. For practical application, the water splitting performance based on NiCoP@PNCNF electrodes was also investigated and exhibited a lower splitting potential (EJ=10, 1.645 V) over long-term stability tests. These insightful findings undoubtedly shed light on the design and fabrication of cost-effective and robust bifunctional transition-metal phosphides electrocatalysts.