In Situ Self-Template Synthesis of Fe–N-Doped Double-Shelled Hollow Carbon Microspheres for Oxygen Reduction Reaction

Abstract

Herein, we reported a special Fe-N-doped double-shelled hollow carbon microsphere (Fe-N-DSC) which was prepared by a facile, in situ polymerization followed by pyrolysis. With porous ferroferric oxide (FeO) hollow microspheres as the templates, where pyrrole monomers were dispersed around the outer surface and prefilled the interior space. By adding hydrochloric acid, Fe ions were released to initiate polymerization of pyrrole on both the outer and inner surfaces of FeO microspheres until they were completely dissolved, resulting in the Fe-containing polypyrrole double-shelled hollow carbon microspheres (Fe-PPY-DSC). The Fe-PPY-DSC was then pyrolyzed to generate the Fe-N-DSC. The FeO hollow microspheres played trifunctional roles, i.e., the template to prepare a double-shelled hollow spherical structure, the initiator (i.e., Fe ions) for the polymerization of pyrrole, and the Fe source for doping. The Fe-N-DSC exhibited a superior catalytic activity for oxygen reduction as comparable to commercial Pt/C catalysts in both alkaline and acidic media. The high catalytic performance was ascribed to the special porous double-shelled hollow spherical structure, which provided more active sites and was beneficial to a high-flux mass transportation.

Fe/Fe3C Nanoparticles Encapsulated in N‐Doped Hollow Carbon Spheres as Efficient Electrocatalysts for the Oxygen Reduction Reaction over a Wide pH Range

“…It can be also seen that some pores appear on the surface of the hollow spheres, which might be caused by the oxidative gases (NO 2 , NO, etc.) released by Fe(NO 3 ) 3 at high calcination temperatures . The existence of such pores could be favorable for providing more accessible active sites and improving the mass transfer efficiency, thereby enhancing the electrocatalytic ORR performance …”

“…Herein, we demonstrate the rational construction of Fe‐N‐C ORR catalysts with hollow spherical structures, which contain Fe/Fe 3 C nanoparticles and Fe‐N x configuration (named as Fe/Fe 3 C/NHCS) and can operate over a wide pH range. It is worth mentioning that hollow carbon spheres (HCS), a promising structure with many accessible active sites and large specific surface area, were deliberately selected as the supporting material for ORR catalysis as recent reports have proved the successful application of HCS in the fabrication of high‐performance Fe‐N‐C catalysts . Feng's group reported a Fe‐N‐C ORR catalyst containing Fe‐N x sites by utilizing core–shell CdS@SiO 2 as the template .…”

Template‐free synthesis of novel hollow carbon nanospheres with dual active sites as catalyst for fuel cell cathode to improve oxygen reduction reaction performances

“…The morphology and structure results indicate that thermal decomposition temperature has played a very important role for the formation of hollow structure. 37,38 In order to prove the role of CTAB reagent in the formation of hollow nanospheres, we made comparative experiments and tests. Thus, mesoporous and macroporous structures of HCN-FNFCG-650 can be obviously observed on the radial interconnected hollow shell with an average thickness of about 80 nm.…”

Rational Synthesis of Iron/Nitrogen‐Doped Carbon Catalyst through a Spatial Isolation Strategy for Efficient Oxygen Reduction in Acidic and Alkaline Media

“…The TEM images in Figure b–d show that the Fe/N‐C microspheres display a homogeneous globular structure without any agglomerates; thus indicating the efficient dispersion of Fe atoms in the carbon matrix. The spheres consist of abundant small fragments of graphitic carbon and disordered domains to form a large number of nanopores . The graphitic carbon fragments are the carbonization products of PDA and melamine in PDA‐Fe/Zn‐melamine precursor, whereas the nanopores are believed to be generated due to the evaporation effect of Zn atoms and polymeric matrices (PDA and melamine) at high temperature.…”