不同锰氧化度水钠锰矿的XPS研究

XPS study on birnessites with different average oxidation states

为了了解水钠锰矿八面体空位的具体分布状况以及表面化学性质,采用X线光电子能谱技术（XPS）对不同锰氧化度水钠锰矿表面Mn与O元素的化学状态进行研究;探讨水钠锰矿结构中空位的分布状况,并建立结构模型。研究结果表明：在高真空测试环境下,在不同锰氧化度水钠锰矿结构中,Mn存在饱和配位和不饱和配位2种化学状态,其含量（摩尔数分数,下同）分别为83.79%-91.69%和8.31%-17.21%;对于锰氧化度较高的水钠锰矿,不饱和配位Mn的含量较小;O以晶格氧、羟基氧和水分子中氧3种化学状态存在,其含量分别为50.44%-65.05%,24.90%-39.27%和8.07%-12.63%;对于锰氧化度较高的水钠锰矿,结构中羟基氧的含量较大;当水钠锰矿沿（110）方向上含Mn^3＋的MnO6八面体链中Mn^3＋含量增大时,结构中空位含量相应减少。

In order to obtain the information on the distribution of vacant sites in birnessite and surface chemistry characteristics of birnessite,the investigation on chemistry states of Mn or O element on the surface of birnessites with different Mn average oxidation states（AOS） was carried out by X-ray photoelectron spectroscopy（XPS）.Structure models of birnessites were presumed.The results indicate that there are two chemistry states of Mn,i.e.,saturated and undersaturated coordinately Mn,whose relative contents are 83.79%-91.69% and 8.31%-17.21%,respectively.The relative content of undersaturated coordinately Mn decreases with the increase of AOS in birnessite.There are three chemistry states of oxygen,i.e.,lattice oxygen,hydroxide and H2O,whose relative contents are 50.44%-65.05%,24.90%-39.27% and 8.07%-12.63%,respectively.The relative content of chemistry state of hydroxide increases with the increase of AOS in birnessite.The vacant sites decreases with the increase of the Mn^3＋ relative content in the Mn^3＋-rich MnO6 rows.