De Jesús Báez Luis R, Rosas Alyssa S, Mahale Pratibha, Mallouk Thomas E
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
Department of Chemistry, University at Buffalo, Buffalo, New York 14260, United States.
ACS Omega. 2023 Oct 24;8(44):41969-41976. doi: 10.1021/acsomega.3c07442. eCollection 2023 Nov 7.
MXenes are of much interest because of their electrochemical, electronic, and surface chemical properties that arise from their structure and stoichiometry. The integrity and the nature of the terminal groups on the basal planes of MXene sheets depend strongly on the method used to etch the parent MAX (M = transition metal, A = Al, X = C, N, B) compound. Aluminum removal typically involves a high concentration of aqueous HF, HCl/LiF mixtures, or fluoride solutions of strong acids. HF etching is problematic because it leaves insoluble AlF in the product, degrades the crystallinity of the nanosheets, and results in the termination of the basal planes with F, O, or OH groups. Here, we demonstrate the use of HF at a low concentration in tandem with a chelating agent, ,'-dihydroxyoctanediamide (suberohydroxamic acid), to selectively etch the archetypical MAX compound TiAlC at room temperature. X-ray absorption spectroscopy (XAS) of the etched materials shows that the carbide nature of bonding in the parent MAX structure is retained in the MXene layers. The stability of the MXene in aqueous suspensions is also significantly improved relative to MXene products made by etching in concentrated HF solutions.
MXenes因其结构和化学计量比所产生的电化学、电子和表面化学性质而备受关注。MXene薄片基面末端基团的完整性和性质在很大程度上取决于用于蚀刻母体MAX(M = 过渡金属,A = Al,X = C、N、B)化合物的方法。去除铝通常涉及高浓度的氢氟酸水溶液、盐酸/氟化锂混合物或强酸的氟化物溶液。氢氟酸蚀刻存在问题,因为它会在产物中留下不溶性的氟化铝,降低纳米片的结晶度,并导致基面以氟、氧或羟基终止。在此,我们展示了在室温下使用低浓度氢氟酸与螯合剂N,N'-二羟基辛二酰胺(辛二羟肟酸)协同作用,以选择性蚀刻典型的MAX化合物TiAlC。蚀刻材料的X射线吸收光谱(XAS)表明,母体MAX结构中键合的碳化物性质在MXene层中得以保留。相对于在浓氢氟酸溶液中蚀刻制成的MXene产物,MXene在水性悬浮液中的稳定性也显著提高。