Spinel NiFe2O4 nanoparticles decorated 2D Ti3C2 MXene sheets for efficient water splitting: Experiments and theories

Abstract

Design and demonstration of cost-effective, robust, and earth-abundant electrocatalysts for efficient water splitting have attracted a great deal of interest. Herein, we have decorated NiFe2O4 nanoparticles on the emerging novel two-dimensional (2D) Ti3C2 (MXene) sheets in order to achieve better electrocatalytic performance for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The synthesized NiFe2O4/Ti3C2 composite showed extraordinary kinetic metrics for electrocatalytic OER, revealing a low overpotential of 266 mV at a current density of 10 mA/cm2, and a small Tafel slope of 73.6 mV/dec. For HER, the composite exhibited an overpotential of 173 mV at 10 mA/cm2 with a small Tafel slope of 112.2 mV/dec. The high electrocatalytic performance of NiFe2O4/Ti3C2 composite is believed to be originated from a well-constructed nanoparticle-sheet interface, synergistic effect, and the high metallic conductivity of Ti3C2 MXene sheets. These experimental results are further supported by the state-of-the-art density functional theory (DFT) simulations. The study providing information about the structure, electronic properties, bonding, and interaction mechanism between Ti3C2 (MXene) and NiFe2O4. Moreover, offering the values of the theoretical overpotential of Ti3C2 (MXene), NiFe2O4, and the NiFe2O4/Ti3C2 composite for both OER and HER activities. Interestingly, the theoretical overpotential follows the qualitative trend of NiFe2O4/Ti3C2 < NiFe2O4 < Ti3C2 MXene for OER and NiFe2O4/Ti3C2 < Ti3C2 MXene < NiFe2O4 for HER, agreeing with the experimental observations. There is charge transfer from NiFe2O4 to MXene leading to enhancement in electronic states near Fermi level which may be due to interactions between C 2p orbital of Ti3C2 MXene and 3d orbital of Ni and Fe. Therefore, this work provides new insights for designing new efficient non-noble metal-based electrocatalysts in the future.