In situ surface-confined fabrication of single atomic Fe-N_(4) on N-doped carbon nanoleaves for oxygen reduction reaction

Controllable fabrication of Fe-N-C based single-atom catalysts(SACs)for enhanced electrocatalytic performance is highly desirable but still challenging.Here,an in situ surface-confined strategy was demonstrated for the synthesis of single atomic Fe-N_(4))on N-doped carbon nanoleaves(L-FeNC).The in situ generated Zn3[Fe(CN)6]2 could not only serve as a protection layer against collapse of nanoleaves but also provide abundant Fe source for the formation of Fe-N moieties during pyrolysis,leading to high surface area and high graphitization degree of L-FeNC simultaneously.Benefiting from abundant Fe-N_(4))active sites,enhanced mass and charge transfer,the as-prepared L-FeNC manifested a half-wave potential of 0.89 V for oxygen reduction reaction(ORR)in 0.1 M KOH.A maximum power density of 140 m W cm^(-2)and stable discharge voltage even after operation for 50,000 s have been demonstrated when the L-FeNC was used as air cathode for Zn-air battery.This work not only provided a unique surfaceconfined strategy for the synthesis of two-dimensional nanocarbons,but also demonstrated the significant benefit from rational design and engineering of Fe-N-C SACs,thus offering great opportunities for fabrication of efficient energy conversion and storage devices.

Self-templated formation of cobalt-embedded hollow N-doped carbon spheres for efficient oxygen reduction

The slow kinetics at the cathode of oxygen reduction reaction(ORR)seriously limits the efficiencies of fuel cells and metal-air batteries.Pt,the state-of-the-art ORR electrocatalyst,suffers from high cost,low earth abundance,and poor stability.Here a self-templated strategy based on metal-organic frameworks(MOFs)is proposed for the fabrication of hollow nitrogen-doped carbon spheres that are embedded with cobalt nanoparticles(Co/HNC).The Co/HNC manifests better ORR activities,methanol tolerance,and stability than commercial Pt/C.The high ORR performance of Co/NHC can be attributed to the hollow structure which provides enlarged electrochemically active surface area,the formation of more Co-N species,and the introduction of defects.This work highlights the significance of rational engineering of MOFs for enhanced ORR activity and stability and offers new routes to the design and synthesis of high-performance electrocatalysts.