石墨烯模板法制备类似三明治结构的多孔碳纳米片用于高效催化酸/碱性条件下氧还原反应的研究(英文)

Graphene-templated synthesis of sandwich-like porous carbon nanosheets for efficient oxygen reduction reaction in both alkaline and acidic media

开发低成本,高性能氧还原反应(ORR)电催化剂对于燃料电池和金属空气电池的规模化应用至关重要.基于石墨烯的碳催化剂已经被广泛用于碱性电解质中的ORR.然而,与Pt/C催化剂相比,石墨烯基催化剂在酸性电解质中的性能仍然需要进一步提升.在这个工作中,我们发展了一种非常高效的模板方法来制备基于石墨烯的具有三明治结构的多孔碳纳米片电催化剂,其在碱性和酸性电解质中均具有非常好的ORR催化性能.首先,被氧化石墨烯吸附的苯二胺分子通过氧化聚合形成富氮聚合物网络,接着铁(Fe)盐被吸附到聚合物网络中,并且在热解之后形成ORR活性位点Fe–N–C以及Fe,Fe S和Fe N0.05纳米颗粒,最终得到类似三明治结构的碳纳米片ORR电催化剂.由于这种结构中存在较高密度的ORR活性位点,所获得的催化剂显示出非常高效的ORR活性,在0.1 mol L^(-1)KOH中半波电位比Pt/C高30 m V.更重要的是,在0.1 mol L^(-1)HCl O_4中,催化剂的半波电位仅比Pt/C低约40 m V.这种独特的平面三明治结构可以在催化反应中暴露出丰富的ORR活性位点,同时,石墨烯层和多孔结构可以提高电导率以及促进传质,这两者对于实现高活性ORR催化至关重要.在碱性和酸性条件中,突出的电催化活性和耐久性表明这些碳纳米片作为贵金属基ORR催化剂的替代物具有很大的潜力,优秀的锌空气电池和质子交换膜燃料电池性能直接证实这种材料在实际电化学能源转化装置中也非常有应用前景.

Developing low-cost, high-performance elec- trocatalysts for the oxygen reduction reaction （ORR） is crucial for implementation of fuel cells and metal-air batteries into practical applications. Graphene-based catalysts have been extensively investigated for ORR in alkaline electrolytes. However, their performance in acidic electrolytes still requires further improvement compared to the Pt/C catalyst. Here we report a self-templating approach to prepare graphene-based sandwich-like porous carbon nanosheets for efficient ORR in both alkaline and acidic electrolytes. Graphene oxides were first used to adsorb m-phenylenediamine molecules which can form a nitrogen-rich polymer network after oxidative poly- merization. Then iron （Fe） salt was introduced into the polymer network and transformed into ORR active Fe-N-C sites along with Fe, FeS, and FEN0.05 nanopartides after pyr- olysis, generating ORR active sandwich-like carbon na- nosheets. Due to the presence of multiple ORR active sites. The as-obtained catalyst exhibited prominent ORR activity with a half-wave potential -30 mV more positive than Pt/C in 0.1 mol L-1 KOH, while the half-wave potential of the catalyst was only -40 mV lower than that of commercial Pt/C in 0.1 mol L-1 HClO4. The unique planar sandwich-like structure could expose abundant active sites for ORR. Meanwhile, the graphene layer and porous structure could simultaneously enhance electrical conductivity and facilitate mass transport. The prominent electrocatalytic activity and durability in both alkaline and acidic electrolytes indicate that these carbon na- nosheets hold great potential as alternatives to precious metal- based catalysts, as demonstrated in zinc-air batteries and proton exchange membrane fuel cells.