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.