Hematite-nickel oxide/carbon nanotube composite catalyst for oxygen evolution reaction

Abstract

In this study, we synthesized hematite (α-Fe2O3) via a simple hydrothermal method and then combined it with nickel oxide (NiO) and carbon nanotubes (CNT) to synthesize a catalyst (α-Fe2O3–NiO/CNT) for the oxygen evolution reaction (OER). The α-Fe2O3–NiO/CNT catalyst exhibited fast electron transfer and high electrical conductivity due to CNT that acted as a conducting network or bridge between the agglomerates α-Fe2O3 and NiO nanoparticles in the composite. It demonstrated outstanding OER catalytic activity and fast reaction kinetics due to the synergistic effect of one component serving as a high electrical conducting network and other providing electrocatalytic properties, which leads to low overpotential of 130 mV (1.36 V vs RHE) and low Tafel slope (60 mVdec−1), considerably lower than that of commercial IrO2, that demonstrated the overpotential of 340 mV (1.57 V vs RHE) with Tafel slope of 69 mVdec−1. Moreover, it exhibited remarkable stability and durability of 96% and retained 97% of its initial catalytic activity after 24 h at constant potential (1.36 V) and current density (10 mA cm−2). Thus, the α-Fe2O3–NiO/CNT catalyst can replace expensive noble metals as highly efficient OER electrocatalysts.