Ultra-small NiFe-layered double hydroxide nanoparticles confined in ordered mesoporous carbon as efficient electrocatalyst for oxygen evolution reaction

Abstract

Nickel–iron layered double hydroxide (NiFe-LDH) is regarded as a promising oxygen evolution reaction (OER) catalyst due to high abundance, low cost and flexible electronic structure. Nevertheless, the limited edge active sites and intrinsic low conductivity seriously hinder its catalytic activity. Herein, we fabricated a highly active catalyst by entrapping NiFe-LDH nanoparticles in ordered mesoporous carbon (OMC) for OER. The mesopores of OMC as nanoreactors can spatially restrict the growth of NiFe-LDH, enabling the formation of ultra-small (~5 nm) nanoparticles. Compared with two-dimensional nanosheets, the NiFe-LDH nanoparticles with less shape anisotropy expose more edge atoms as catalytic active sites. In addition, the NiFe-LDH particles in-situ grown in the pores form intimate contact with the carbon, which triggers the transfer of electrons from NiFe-LDH to OMC and promotes the adsorption of OH−, further accelerating OER kinetics. The catalyst exhibited outstanding catalytic performance towards the OER, delivering 10 and 100 mA cm−2 current density at 223 and 296 mV overpotential, respectively, as well as low Tafel slope 56.6 mV dec−1. Moreover, its mass activity is more than eight times higher that of NiFe-LDH nanosheets (at 300 mV overpotential).