An investigation of Fe incorporation on the activity and stability of homogeneous (FexNi1-x)2P solid solutions as electrocatalysts for alkaline hydrogen evolution

Abstract

Ni2P has been intensively investigated for hydrogen evolution reaction (HER) in recent years since the HER activity of Ni2P (001) is theoretically superior to Pt. Most of these works have focused on acid system as Ni2P is unstable in alkaline media. However, alkaline water splitting is more practical for industry due to the lack of suitable acidic oxygen evolution catalyst. Thus, providing an efficient alkaline HER catalyst by enhancing the stability and activity of Ni2P is needed. Herein, we have grown mesoporous (FexNi1-x)2P nanosheets on Ni foam (NF) as HER catalyst with activities being related to Fe/Ni ratio. FeNiP/NF with Fe/Ni ratio of 5/5 and high-density exposure of (001) surface shows much better stability and HER activity in alkaline than Ni2P. Our experimental results reveal that the homogeneous lattice substitution of Fe modified the electronic structure of Ni2P, enhanced the intrinsic activity and the number of active sites. Density functional theory calculation reveals that the Fe incorporation improves the HER activity of the highly exposed FeNiP (001) surface by reducing the energy barriers of HER reactants (H and H2O) adsorption compared with Ni2P. This work provides an effective pathway for the future development of HER catalyst in alkaline conditions by introducing hetero-atom into the host lattice.