Carbon Nanofiber-Encapsulated FeCoNiCuMn Sulfides with Tunable S Doping for Enhanced Oxygen Evolution Reaction

The oxygen evolution reaction (OER) stands out as a key electrochemical process for the conversion of clean energy. However, the practical implementation of OER is frequently impeded by its slow kinetics and the necessity for scarce and expensive noble metal catalysts. High-entropy transition metal sulfides (HETMS) stand at the forefront of OER catalysts, renowned for their exceptional catalytic performance and diversity. Herein, we have synthesized a HETMS catalyst, (FeCoNiCuMn50)S2, encapsulated within carbon nanofibers through a one-step process involving the synergistic application of electrospinning and chemical vapor deposition. By precisely controlling the doping levels of sulfur, we have demonstrated that sulfur incorporation significantly increases the exposed surface area of alloy particles on carbon nanofibers and optimizes the electronic configuration of the alloy elements. These findings reveal that sulfur doping is instrumental in the substantial improvement of the catalyst’s OER performance. Notably, the catalyst showed optimal activity at a sulfur-to-metal atom ratio of 2:1, delivering an overpotential of 254 mV at a current density of 10 mA cm−2 in 1.0 M KOH solution. Furthermore, the (FeCoNiCuMn50)S2 catalyst exhibited remarkable electrochemical stability, underscoring its potential as an efficient and robust OER electrocatalyst for sustainable energy applications.