A simple and effective method for constructing highly efficient oxygen reduction catalysts with trace amount of isolated cobalt was firstly developed by the pyrolysis of Co-centered polyoxometalate@metal-organic framework (Co-POM@MOF). The Co-centered polyoxometalate ([CoW12O40]6−) was confined in the well-defined void space of ZIF-8 to achieve homogeneous dispersion of polyoxoanions, where the isolated Co centers were well surrounded by the W-O shell and ZIF-8 framework. The Co-POM@MOF-derived N-doping porous carbon (Co-W-NC) with trace cobalt content was facilely prepared by the pyrolysis of the Co-POM@MOF under Ar atmosphere. The single dispersion of polyoxoanions in the metal-organic framework with complete separation of Co center surrounding by W-O shell and ZIF-8 framework ensures the uniform dispersion of Co atoms, confirmed by the Fourier transform extended X-ray absorption fine structure measurement. The Co-W-NC composite catalysts exhibit high performance for oxygen reduction reactions with a half-wave potential of 0.835 V in 0.1 mol/L KOH solution with excellent durability, which is much superior to that of the control samples derived from the [PW12O40]@ZIF-8, and the commercial Pt/C. This work highlights a new insight for constructing highly efficient catalysts via the introduction of metal-centered polyoxometalate into metal-organic framework following the high temperature treatment process.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |