Carbon Nanotubes/Heteroatom‐Doped Carbon Core–Sheath Nanostructures as Highly Active,Metal‐Free Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells

A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom‐doped carbon (CNT/HDC) core–sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom‐containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom‐containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom‐doped nanocarbon catalysts in terms of half‐wave potential and kinetic current density. The four‐electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long‐term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites.     

Isolated Single Iron Atoms Anchored on N‐Doped Porous Carbon as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

The development of low‐cost, efficient, and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. Herein, we made a highly reactive and stable isolated single‐atom Fe/N‐doped porous carbon (ISA Fe/CN) catalyst with Fe loading up to 2.16 wt %. The catalyst showed excellent ORR performance with a half‐wave potential (E _1/2) of 0.900 V, which outperformed commercial Pt/C and most non‐precious‐metal catalysts reported to date. Besides exceptionally high kinetic current density (J _k) of 37.83 mV cm⁻² at 0.85 V, it also had a good methanol tolerance and outstanding stability. Experiments demonstrated that maintaining the Fe as isolated atoms and incorporating nitrogen was essential to deliver the high performance. First principle calculations further attributed the high reactivity to the high efficiency of the single Fe atoms in transporting electrons to the adsorbed OH species.     

Stereoselectively Assembled Metal–Organic Framework (MOF) Host for Catalytic Synthesis of Carbon Hybrids for Alkaline‐Metal‐Ion Batteries

Cost‐effective metal‐based nanostructured hybrids have been widely dedicated to potential energy storage and conversion applications. Herein, we develop a facile methodology for the synthesis of precise carbon‐confined hybrid nanostructures by stereoselective assembly accompanied by catalytic pyrolysis. Polyacrylonitrile fiber films favors not only metal‐polymer coordination, but also oriented assembly to ensure the well‐defined nanostructure of the carbon hybrids. During chemical vapor deposition (CVD), cobalt‐nanoparticle‐catalyzed growth of carbon‐nanotube branches driven by organic molecules (e.g. melamine) delivers hierarchical carbon hybrids. The resulting carbon hybrids exhibit outstanding electrochemical performance for metal‐ion batteries, for example, a high specific capacity of 680 mAh g^?1 after 320 cycles (Li‐storage) and 220 mAh g^?1 after 500 cycles (Na‐storage) without decay.