Anion/cation-induced strong electronic polarization of N,Fe-CoS₂ electrocatalyst to boost efficient oxygen evolution

Designing and developing the high activity and long-term durability electrocatalysts for oxygen evolution reaction (OER) has primary significance for breaking the bottleneck of water electrolysis. Herein, an anion/cation-codoped CoS₂ based electrocatalyst, N,Fe-CoS₂, for the efficient OER was constructed via two-step electrodeposition and low-temperature calcination. The anion and cation optimized significantly the surface electronic structure of N,Fe-CoS₂ and induced synergistically a strong surface electronic polarization along with the generation of abundant Co³⁺ active sites, which improved considerably the intrinsic catalytic activity. The doping N anion also hindered effectively the catalyst surface oxidation and enhanced the catalytic durability. Benefiting from these, N,Fe-CoS₂ exhibited the outstanding OER activity and catalytic durability, and especially at a high current density, acquired its ultra-low OER overpotential of 261 mV at 300 mA∙cm^-2 and maintained continuously a stable current density for 80 h without visible attenuation at 100 mA∙cm^-2. DFT calculations confirmed the cooperative effect of N anions and Fe cations on improving catalytic activity and unveiled that Fe cations in N,Fe-CoS₂ acted a key role in modulating electron densities instead of acting as catalytic sites. This work has an important implication for realizing the synergistic regulation of electron densities of catalytic materials by anions and cations.