Nitrogen-Fluorine Dual Doped Porous Carbon Derived from Silk Cotton as Efficient Oxygen Reduction Catalyst for Polymer Electrolyte Fuel Cells

Porous carbon derived from silk cotton and heteroatom engineering is explored in this study for developing metal-free electrocatalysts for oxygen reduction (ORR). Individual and dual doping of N and F heteroatoms was conducted to regulate defects and the pore geometry to the porous carbon matrix. Microscopic analysis of N-F co-doped cotton carbon (N-F/CTC) undergoes morphological amendments in its textural properties and defects responsible in creating active sites for ORR. N-F/CTC catalyst exhibits excellent ORR catalytic activity and methanol and CO tolerance in the alkaline medium, which makes it a potential metal-free ORR catalyst for the polymer electrolyte membrane fuel cell. N-F/CTC catalyst is subjected to 10 000 repeated potential cycles with no degradation in its activity. XPS analysis of N-F/CTC catalyst revealed the presence of N in the form of pyridinic-N, pyrrolic-N, graphitic-N, active species, and F in the form of C-F ionic and C-F semi-ionic active forms. The maximum C-C bond polarization, charge redistribution, and high spin densities in the carbon matrices are attained by all these active forms present in the catalyst and synergistically enhance the ORR activity.