NiFe2O4 spinel ferrite and h-BN nanosheets coalescence for superior electrocatalytic oxygen evolution reaction

Abstract

In electrocatalyst based water electrolysis, the half reaction of oxygen evolution has slow kinetics compared to the other half reaction of hydrogen production. The use of metal oxide hybridized heterostructure (HS) catalyst is considered as cost-effective strategy for oxygen evolution applications than the noble metal catalyst. Here, we synthesized nickel ferrite (NiFe₂O₄) nanoparticles by thermal decomposition of citrate complex of corresponding metals. Further, nickel ferrite/boron nitrite (NiFe₂O₄/h-BN) heterostructure catalysts were synthesized by the exfoliation method (ultrasonication) with different ratio of h-BN (75 mg and 150 mg). The prepared heterostructure catalysts were characterized using Fourier-transform infrared (FTIR) spectroscopy to study the chemical bonding. X-ray diffraction spectroscopy (XRD) confirmed that the crystal structure of NiFe₂O₄ as a spinel ferrite. High resolution scanning electron microscopy (HRSEM) images revealed that NiFe₂O₄ nanoparticles were embedded on the surface of BN nanosheets. X-ray Photoelectron spectroscopy (XPS) was used to analysis the oxidation states of the constituent elements. Brunauer-Emmett-Teller (BET) was conducted to study the porosity and surface area of developed HS, it's revealed that NiFe₂O₄/h-BN-75 HS had higher pore volume and pore size (0.037 cm³/g and 3.5 nm) than bare NiFe₂O₄. All the electrocatalysts were loaded on the carbon cloth to make electrodes for oxygen evolution reaction analysis. The electrochemical measurements were conducted to explore the electrocatalytic behaviour of carbon cloth loaded electrodes. NiFe₂O₄/h-BN-75 heterostructure catalyst showed reduced overpotential ∼431 mV with lower Tafel slope and lower charge transfer resistance values of 127.8 mV dec⁻¹ and 9.6 Ω, respectively. These properties of NiFe₂O₄/h-BN-75 significantly enhanced the kinetics of oxygen evolution reaction than the bare NiFe₂O₄ nanoparticles. These results, demonstrate that the synthesis and fabrication methods are significant to improve the electrocatalytic behavior of heterostructure catalyst with cost effectiveness.