One-pot synthesis of diiron phosphide/nitrogen-doped graphene nanocomposite for effective hydrogen generation

Abstract

A nanocomposite comprising diiron phosphide (Fe2P) nanoparticles and nitrogen-doped graphene (NGr) was synthesized by a facile one-pot reaction. Such a nanocomposite showed efficient electrocatalytic activity in hydrogen evolution reaction (HER) in both acidic and basic solutions. The optimal overpotential required for the current density of 20mAcm−2 (η20) in acidic solution is 164mV, which is favourably comparable to those of recently reported non-precious electrocatalysts; whereas in basic solution the value of η20 is 376mV. The HER activity of Fe2P/NGr can be correlated to Fe2P nanoparticles in the nanocomposite, and NGr is beneficial to the electron transport from electrode to the catalyst. The faradaic efficiency of Fe2P/NGr nanocomposite in HER is nearly 100% in both acidic and basic solutions. The stability of Fe2P/NGr nanocomposite during HER has been demonstrated by potentiostatic electrolysis and accelerated degradation experiments. Tafel slope was determined to be 65mVdec−1, which suggests that the HER processes might proceed along a Volmer–Heyrovsky mechanism. The catalytic activity of Fe2P/NGr nanocomposite is influenced by synthesis temperature, which may result in the differences in phase purity, particle size and specific surface areas of the composite material. The charged natures of Fe and P in Fe2P nanoparticle might be responsible for the HER activity of Fe2P/NGr nanocomposite.