MnO_2动态催化氧还原的研究

Study on oxygen reduction with MnO_2 dynamic catalyze

为了提高MnO2催化氧还原效率，采用Ⅸ改性MnO2经350℃高温处理后作为氧还原的催化剂，草酸铵造孔剂及MWNTs为复合电催化剂，氧电极可获得50mA／em。的工作电流密度（-200mV）。Bi改性MnO2的微观形貌分析表明，其晶体颗粒尺度约100nm，且粒径分布较均匀，呈自然团聚外貌，团聚物直径在2～8μm。Bi改性MnO2催化氧还原机理为：在放电过程中，由于Bi改性的MnO2具有良好的可逆性能，因此O2在MnO2上发生的电子得失过程是瞬间过程，而不是MnO2的晶格转变，仅仅是质子-电子的传递。当缺氧时，MnO2发生还原反应，才会发生晶格转变。

A new compound catalyst was used to improve the efficiency of oxygen electroreduction on the MnO2 electrode, this compound catalyst mainly consisted MnO2 modified with Bi after treating with 350℃, and （NH4）2Ac as pore-forming agent and MWNTs as assistant catalyst, the working current density on oxygen electrode was 50 mA/cm^2 （ - 200 mV）. The microcosmic morphology of MnO2 modified with Bi was studied by SEM. The results found out that the scale of the MnO2 grains has a size about 100 nm,the grains had a narrow size distribution and reunited, particle dusters has a size between 2 μm and 8μm. The mechanism of the electrochemical reduction of oxygen on the MnO2 modified with Bi was concluded. In a discharging process, because of MnO2 modified with Bi having a high reversibility, the charge transfer step of 02 on MnO2 was a stage of proton-electron transfer, which was a transient step, but not a step of MnO2 lattice transformation. The MnO2 lattice transformation only occurred in a reduction process of MnO2 under the condition of oxygen lack.