Wang Jiacheng, Ma Ruguang, Zhou Zhenzhen, Liu Guanghui, Liu Qian
1] State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, P. R. China [2] Innovation Center for Inorganic Materials Genomic Science, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, P. R. China [3] Shanghai Institute of Materials Genome, Shanghai, P. R. China.
Sci Rep. 2015 Mar 20;5:9304. doi: 10.1038/srep09304.
Efficient metal-free electrocatalysts for oxygen reduction reaction (ORR) are highly expected in future low-cost energy systems. We have successfully prepared crumpled, sheet-like, sulfur-doped graphene by magnesiothermic reduction of easily available, low-cost, nontoxic CO2 (in the form of Na2CO3) and Na2SO4 as the carbon and sulfur sources, respectively. At high temperature, Mg can reduce not only carbon in the oxidation state of +4 in CO3(2-) to form graphene, but also sulfur in SO4(2-) from its highest (+6) to lowest valence which was hybridized into the carbon sp(2) framework. Various characterization results show that sulfur-doped graphene with only few layers has an appropriate sulfur content, hierarchically robust porous structure, large surface area/pore volume, and highly graphitized textures. The S-doped graphene samples exhibit not only a high activity for ORR with a four-electron pathway, but also superior durability and tolerance to MeOH crossover to 40% Pt/C. This is mainly ascribed to the combination of sulfur-related active sites and hierarchical porous textures, facilitating fast diffusion of oxygen molecules and electrolyte to catalytic sites and release of products from the sites.
在未来低成本能源系统中，高效的无金属氧还原反应（ORR）电催化剂备受期待。我们通过镁热还原法，分别以易得、低成本、无毒的二氧化碳（以Na₂CO₃形式）和Na₂SO₄作为碳源和硫源，成功制备出了褶皱状、片状的硫掺杂石墨烯。在高温下，Mg不仅能将CO₃²⁻中处于+4氧化态的碳还原以形成石墨烯，还能将SO₄²⁻中的硫从其最高价态（+6价）还原到最低价态，并杂化进入碳的sp²骨架。各种表征结果表明，层数较少的硫掺杂石墨烯具有合适的硫含量、层次分明的坚固多孔结构、大的表面积/孔体积以及高度石墨化的纹理。S掺杂石墨烯样品不仅对ORR具有通过四电子途径的高活性，而且具有优于40% Pt/C的耐久性和对甲醇渗透的耐受性。这主要归因于硫相关活性位点与层次多孔结构的结合，有利于氧分子和电解质快速扩散到催化位点以及产物从这些位点释放。
