NiFe-spinel oxides with nitrogen-doped carbon quantum dots for enhanced oxygen evolution activity

Abstract

Designing efficient and stable electro-catalysts for non-precious metal oxygen evolution reactions (OER) is critical to solve the bottleneck of water splitting. The NiFe2O4/NCQDs composite electrode was fabricated by combining nitrogen doped carbon quantum dots (NCQDs) with NiFe2O4 spinel via a hydrothermal method, which showed brilliant OER catalytic performance by modifying on nickel foams (NF). The composites had petal-like structures, and the NiFe2O4 was epitaxially grown on the NF substrates with exposed sites, resulting in enhanced electron transport. The fluorescence quenching of NCQDs was accompanied by binding NCQDs with NiFe2O4, which indicated the energy barrier was greatly reduced during the electron transport as well as electro-catalysis. The higher intrinsic charge transfer was achieved, and the doping combination having a higher conductivity was confirmed. The electrochemical activity of NiFe2O4/NCQDs electrode in OER reaction was evaluated under alkaline conditions. The addition of NCQDs effectively enhanced the OER activity, and over-potentials were decreased from 330 mV to 270 mV at 10 mA cm−2 with Tafel slope lower (66 mV/dec) than counterparts. The NiFe2O4/NCQDs displayed long-term catalytic stability at 1.47 V. Therefore, a facile method for preparing NiFe2O4/NCQDs was developed which had characteristics of low cost, simple process and excellent OER activity.