Sulfur-doped NiFe(CN)5NO nanoparticles as efficient electrocatalysts for the oxygen evolution reaction

Abstract

Developing low-cost and high-efficiency electrocatalytic materials for the oxygen evolution reaction (OER) is crucial and urgent for water splitting. Here, we demonstrate a novel OER electrocatalyst (S–NiFe(CN)₅NO) prepared by constructing a bimetallic metal–organic framework (MOF) and in situ doping of sulfur. The generation of Ni–Fe active sites upgrades the structural stability and electronic conductivity of the MOF. The sulfur doping further optimizes the electronic structure, thus lowering the energy barriers for the OER. As a result, the S–NiFe(CN)₅NO catalyst possesses excellent catalytic activity towards the OER with an ultralow overpotential of 274 mV at 10 mA cm⁻² and a small Tafel slope of 54.4 mV dec⁻¹ in 1.0 M KOH. Moreover, the activity can be well maintained after 1000 cycles, indicating superior electrochemical stability. The electrocatalytic performance of S–NiFe(CN)₅NO is far superior to that of pristine NiFe(CN)₅NO and the advanced RuO₂ catalyst. It is revealed that the improved OER catalytic properties are attributed to the synergetic effect of bimetallic active sites and sulfur species in S–NiFe(CN)₅NO. Density functional theory calculations explain that S doping can accelerate electron transport and optimize OER paths. This work is meaningful for the study of many multivariate MOFs as OER catalysts and can be extended to other energy-related fields.