In-situ formation of hierarchical 1D-3D hybridized carbon nanostructure supported nonnoble transition metals for efficient electrocatalysis of oxygen reaction

Electrocatalysis of oxygen reaction is a critical step in operation of fuel cells and metal-air batteries. For the practical applications, the inexpensive non-noble metals catalysts with highly activity and stable need to be explored and utilized. Herein, a strategy for the preparation of a bi-functional rambutan shaped oxygen electrocatalyst is presented. The novel electrocatalyst is formed in situ with N doped carbon nanotubes grown on metal encapsulated hollow-mesoporous carbon sphere (Me@N-CNT/HMCS). The Me@N-CNT/HMCS oxygen electrocatalysts show high catalytic activities towards ORR, comparable to commercial Pt/C catalyst. The optimized performance of Fe@N-CNT/HMCS was achieved with a positive onset potential of 1.012 V and half-wave potential of 0.833 V. It is emphasized that Me@N-CNT/HMCS shows high stability and enhanced tolerance against methanol in alkaline medium. The Fe@N-CNT/HMCS electrocatalyst possessed a high OER activity with a low overpotential of 0.35 V at 10 mA cm⁻² current density. The excellent performance could be attributed to the synergistic effect involving chemical composition, high conductivity, good porosity and unique rambutan-like structure. In addition, the theoretical calculation study suggests that metallic Fe cluster can promote the O₂ adsorption strength in such chemical environment.