Room temperature two-dimensional ferromagnetic Ni-doped Fe5GeTe2 with tunable Tc for enhanced oxygen evolution reaction

Abstract

Improving the Curie temperature and catalytic performance of two-dimensional magnetic materials through elemental doping is a feasible strategy. In this study, Ni-doped (Fe1−xNix)5GeTe2 (0 ≤ x ≤ 0.3) single crystals were grown via chemical vapor transport method and the amount of Ni doping could be precisely controlled. As the amount of Ni doping increases, the long-range ferromagnetic ordering temperature increased, and (Fe0.7Ni0.3)5GeTe2 exhibited the highest Curie temperature Tc = 492.73 K. The improvement of Tc can be attributed to the occupancy of the Fe1 site by Ni atoms. The oxygen evolution reaction (OER) activities of liquid phase exfoliated (Fe1−xNix)5GeTe2 nanoflakes were enhanced by doping Ni atoms, and the overpotential decrease to 464 mV at 10 mA/cm2 with a small Tafel slope of 41 mV/dec for the (Fe0.9Ni0.1)5GeTe2 nanoflakes. Based on the density functional theory calculations, when half of the Fe1 sites were replaced by Ni atoms, the number of enhanced OER active sites (Fe1-Te sites) reached maximum, and then, (Fe0.9Ni0.1)5GeTe2 exhibited the best catalytic performance. The experimental and theoretical calculation results indicate that replacing Fe1 site with Ni in two-dimensional magnetic Fe5GeTe2 can effectively increase the Curie temperature and enhance OER activity.