Search

High-performance non-noble electrocatalysts for oxygen reduction reaction (ORR) are the prerequisite for large-scale utilization of fuel cells. Herein, a type of sandwiched-like non-noble electrocatalyst with highly dispersed FeNx active sites embedded in a hierarchically porous carbon/graphene heterostructure was fabricated using a bottom-up strategy. The in situ ion substitution of Fe3+ in a nitrogen-containing MOF (ZIF-8) allows the Fe-heteroatoms to be uniformly distributed in the MOF precursor, and the assembly of Fe-doped ZIF-8 nano-crystals with graphene-oxide and in situ reduction of graphene-oxide afford a sandwiched-like Fe-doped ZIF-8/graphene heterostructure. This type of heterostructure enables simultaneous optimization of FeNx active sites, architecture and interface properties for obtaining an electron-catalyst after a one-step carbonization. The synergistic effect of these factors render the resulting catalysts with excellent ORR activities. The half-wave potential of 0.88 V vs. RHE outperforms most of the none-noble metal catalyst and is comparable with the commercial Pt/C (20 wt %) catalyst. Apart from the high activity, this catalyst exhibits excellent durability and good methanol-tolerance. Detailed investigations demonstrate that a moderate content of Fe dopants can effectively increase the intrinsic activities, and the hybridization of graphene can enhance the reaction kinetics of ORR. The strategy proposed in this work gives an inspiration towards developing efficient noble-metal-free electrocatalysts for ORR.

Oxygen evolution reaction (OER) is an important half-cell reaction of the electrical water splitting, for its high overpotential associated with sluggish OER kinetics. Therefore, it is critical to develop highly active and durable electrocatalysts to reduce the overpotential. Herein, ultra-small RuO

Oxygen evolution reaction (OER) is an important half-cell reaction of the electrical water splitting, for its high overpotential associated with sluggish OER kinetics. Therefore, it is critical to develop highly active and durable electrocatalysts to reduce the overpotential. Herein, ultra-small RuO2 nanoparticles (NPs) supported on onion-like carbon (OLC) and carbon nanotube (CNT) are successfully synthesized by means of wet impregnation combined with annealing treatment, respectively. The microstructure characterization results showed OLC perfect graphitic carbon layer structure, and the RuO2 NPs supported on the OLC possess larger particle size compared with the RuO2 NPs supported on the CNT. Moreover, the electronic structure of Ru in RuO2/OLC was also optimized by the OLC support to be beneficial for the OER. The OER performance of the catalysts were investigated in 1 M KOH solution. The results show RuO2/OLC has a comparable OER activity to the commercial RuO2, but a significantly higher mass activity than the commercial RuO2. When compared with the RuO2/CNT, RuO2/OLC not only exhibits lower overpotential and Tafel slop, but also owns more active sites and higher TOF value, indicating the OLC support improved the OER activity of RuO2/OLC. Moreover, RuO2/OLC showed a superior stability compared with RuO2/CNT, which can be attributed to the excellent electrochemical oxidation-resistance of the OLC.