MOF-derived porous Ni2P nanosheets as novel bifunctional electrocatalysts for the hydrogen and oxygen evolution reactions

Transition metal phosphides (TMPs) are considered to be highly-efficient electrochemical catalysts, which have extraordinary capabilities to relieve the energy crisis and have gradually become prime candidates for application in energy conversion and storage devices. In this contribution, we report the preparation of porous Ni2P nanosheets in a controllable manner using NiO-MOF-74 as precursors, followed by a conventional phosphorization strategy. The porous Ni2P nanosheets exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction (HER) with a low overpotential of 168 mV at a current density of 10 mA cm(-2) in 1.0 M KOH and a small Tafel slope of 63 mV dec(-1). The overpotential and Tafel slope of porous Ni2P nanosheets for the oxygen evolution reaction (OER) are 320 mV (10 mA cm(-2)) and 105 mV dec(-1), respectively. In addition, both the HER and OER measurements demonstrate that porous Ni2P nanosheets have superior electrochemical stability in alkaline solution. The desirable electrocatalytic properties of the porous Ni2P nanosheets may be due to their larger surface area and favorable electrical conductivity. The porous structures of the Ni2P nanosheets provide pathways for electron conduction, which facilitates electron transfer and accelerates bubble (H-2 and O-2) diffusion on the surface of the electrode.