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利用密度泛函理论(DFT)+U方法,本文研究了单层Ni–Fe氢氧化物纳米片中阳离子排列方式和表面补偿阴离子对其磁结构和催化性能的影响.Fe原子偏聚引起的无序结构会在纳米片中产生不同自旋排列的磁畤,而表面补偿阴离子会影响Fe原子的局部磁矩和价态.这两种实验条件不会从根本上改变Ni–Fe氢氧化物纳米片中磁性来源,即磁性金属原子间的超交换作用本质,但可在纳米片中形成特性各异的磁性超晶格.此外,氧还原/析出反应中间态自由能变化的计算证实最稳定磁结构的Ni–Fe氢氧化物纳米片具有优异的催化性能,表现出磁催化剂的特性.其原因是反应中Fe~(2+)–Fe~(3+)间价态的循环转变,决定了O–H键断裂和OH基释放的难易程度,从而控制了反应基元限制步的速率.我们可以通过Fe离子价态变化将纳米片的磁性和催化活性联系起来,该认识将有助于打开氢氧化物/LDHs为基的磁性催化剂设计之路.
Using density functional theory (DFT) + U method, the influence of the cation arrangement and surface compensation anion on the magnetic structure and catalytic performance of single-layer Ni-Fe hydroxide nanosheets was studied in this paper. The ordered structure produces different spin-aligned magnetite in the nanosheets, and the surface-compensated anions affect the local magnetic moments and valences of the Fe atoms. These two experimental conditions do not fundamentally change the Ni-Fe hydroxide nano The magnetic origin of the film, the nature of the trans-exchange between the magnetic metal atoms, can be characterized by the formation of magnetic superlattices with different properties in the nanosheet. In addition, the calculation of the free energy change in the intermediate state of the oxygen reduction / precipitation reaction confirms the most stable magnetic The structure of Ni-Fe hydroxide nanosheets has excellent catalytic performance, showing the characteristics of the magnetic catalyst.The reason is that the cyclical transformation of the valence state of Fe ~ (2 +) - Fe ~ (3+) in the reaction determines O-H bond cleavage and OH group release thereby controlling the rate of the reaction-unit-limited step.We can relate the magnetic and catalytic activity of the nanosheet to the valence state of the Fe ion, Open hydroxide / LDHs based Design of the magnetic path of the catalyst.