Effects of steady magnetic fields on NiRuO2 nanofibers for the electrocatalytic hydrogen evolution reaction and oxygen evolution reaction

Abstract

Electrochemical water splitting is a high-potential methodology to sustainable hydrogen production but is constrained by the diminished reaction kinetics of the oxygen evolution reaction (OER). We design a nickel-doped ruthenium dioxide nanofiber electrocatalyst (NiRuO₂ NFs) that demonstrates exceptional OER performance when subjected to external magnetic strength conditions of 800 mT. The catalyst achieves a low overpotential performance with 280 mV for the OER and 1 mV for the HER at a current density of 10 mA cm⁻² and exhibits notable electrochemical stability. Using a combination of quasi-in situ M–T measurements and density functional theory (DFT) calculations, we uncover the mechanism by which the external magnetic field drives a spin state transition from high-spin to low-spin, thereby enhancing the interaction between catalytically active sites and reaction intermediates. We investigate two potential mechanisms, the adsorbate evolution mechanism (AEM) and the oxide path mechanism (OPM), and demonstrate that the magnetic field reduces the Gibbs free energy barriers for both mechanisms. Enhanced hybridization of M-3d and O-2p orbitals under the magnetic field improves electronic coupling and catalytic activity. These discoveries not only establish an innovative theoretical foundation and practical methodology for designing magnetic electrocatalysts, but also uncover the dynamic interplay between spin state modulation, electronic structure evolution, and catalytic mechanisms for the OER. This study offers critical guidance for developing highly efficient, magnetic-tunable electrocatalysts.