Effect of Fe addition on the ORR electrocatalytic activity of precursor‐derived high‐entropy carbide nanocomposites

Abstract High‐entropy carbides (HECs) exhibit enhanced mechanical properties and high temperature oxidation resistance as compared to their binary counterparts. However, their application as catalytic materials was restricted due to a lack of high specific surface area with conventional synthesis methods such as solid‐state sintering. In the present work, porous high‐entropy carbide nanocomposites with varying elemental composition were synthesized through the precursor‐derived ceramic route, and their electrocatalytic activity for the oxygen reduction reaction (ORR) was assessed. Thus, the compositionally complex nanocomposite was prepared from a preceramic precursor, which was, upon modification of a polysiloxane with Ta, V, W, Mo, and Nb‐based organometallic precursors via pyrolysis in an inert atmosphere. The pyrolyzed ceramic was subsequently modified with Fe‐based precursor, with varying quantities and heat‐treated at 1300°C to obtain Fe‐containing high‐entropy carbide nanocomposites. X‐ray diffraction and ADF‐STEM imaging coupled with EDX confirmed the incorporation of Fe into the HEC lattice. The onset potential for the electrocatalytic ORR increased from 0.81 to 0.85 V upon incorporation of Fe into the high‐entropy carbide nanocomposite. Furthermore, with the addition of electron‐rich Fe in HEC nanocomposite, the reaction mechanism moved toward a four‐electron path. This suggests the positive effects of incorporating Fe into HEC nanocomposites.