Efficient Oxygen Electroreduction: Hierarchical Porous Fe–N-doped Hollow Carbon Nanoshells

Hierarchical porous carbon nanoshells with about 40 nm cavities are synthesized by using CdS@mSiO2 core–shell structured materials as hard templates and 4,4′-bipyridine and FeCl3·6H2O as nitrogen, carbon, and iron sources. CdS@mSiO2 denotes a CdS nanoparticle core and mesoporous SiO2 (mSiO2) shell. The obtained porous and hollow carbon nanoshells demonstrate excellent electrocatalytic activity for oxygen reduction reaction (ORR). Both the onset potential (0.98 V) and half-wave potential (0.85 V) are more positive than that of commercial Pt/C in alkaline conditions with the same catalyst loading (0.1 mg cm–2). In acidic conditions, the onset and half-wave potentials of carbon-nanoshell electrodes are only 30 and 20 mV less than that of commercial Pt/C, respectively. The outstanding stability and electrocatalytic activity for ORR of these novel carbon nanoshells can be attributed to the use of a Fe–Nx containing precursor, hierarchical porous structural features, and perhaps most importantly the hollow shell design. Such hollow carbon nanoshells exhibit high performance as electrocatalysts for ORR; also this synthetic approach represents a versatile, new route toward the preparation of efficient materials with hierarchical porous and hollow structural features.