NiCo Alloy Encapsulated in Sulfur and Nitrogen Codoped Carbon Nanofiber as Efficient Oxygen Reduction Electrocatalysts for Direct Methanol Fuel Cells

Abstract

The design and development of highly active and stable oxygen reduction reaction (ORR) catalysts are urgently necessary for the efficient operation of direct methanol fuel cells (DMFCs). In this research, a straightforward electrostatic spinning technique was integrated with a pyrolysis process to synthesize NiCo alloy nanoparticles embedded in sulfur (S) and nitrogen (N) codoped one-dimensional (1D) carbon nanofibers. The peak power density of the DMFC modified with NiCo₂-A@S-NCNFs reached 29.70 mW cm^–2, which is nearly comparable to that of the Pt/C-based DMFC (29.57 mW cm^–2). The augmented ORR activity of NiCo₂-A@S-NCNFs can be attributed to the advantages brought about by the S, N codoped carbon nanofibers and the synergistic interaction with the NiCo alloy. This combination not only supplies a larger quantity of active sites but also facilitates rapid electron and mass transport. Furthermore, the NiCo₂-A@S-NCNFs catalysts demonstrated remarkable durability. The 1D nanofiber interconnect network effectively immobilizes NiCo alloy nanoparticles to prevent agglomeration, forming a stable conductive structure and an efficient electron transport pathway, thereby enhancing the durability of NiCo₂-A@S-NCNFs. This study offers an effective approach for the design of heteroatomically doped carbon materials to enhance the ORR performance of non-noble-metal catalysts in fuel cells.