最后在氩气氛下于900°C的温度下热解后,Fe-Phen @ ZIF-8在氮掺杂碳骨架(Fe-N x - C)上转化为孤立的单原子铁。
2.表征
图4.各表征谱图
对图4阐述分析:
图a:Fe-Phen @ ZIF-8的X射线衍射(XRD)图与纯ZIF-8的X射线衍射图非常匹配,表明其高结晶度和类似的沸石型结构。图b-d:扫描电子显微镜(SEM)和透射电子显微镜(TEM)图像显示,热处理后Fe‐Nx‐C保持其初始十二面体形状,而表面变得更粗糙。图e:高分辨率透射电子显微镜(HRTEM)图像中,石墨碳层的晶向间距为0.34nm。图f:选择区域电子衍射(SAED)图像示出了环,指示整个碳骨架的结晶性差,在900℃热处理过程中形成无结晶的铁。(g,h在Fe - Nx - C的红圈区域,经过像差校正的HAADF‐STEM图像和EELS点谱)。图g:显示出单个的铁原子。图h:表明Fe和N以Fe‐Nx形式共存。之后XPS结果一致,证实了分散良好的Fe原子与N配位。图i:Fe‐Nx ‐C的拉曼光谱在1347和1572 cm -1处显示两个峰,其I D / I G值为2.51,低于N‐C(I D/ I G = 1.86)。D峰表示晶格的缺陷。该结果表明,在碳骨架中引入铁原子诱导了碳基质的缺陷位点的形成,据报道该缺陷位点是氧电极的活性位点。
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