Experimental and theoretical investigation of the chemical exfoliation of Cr-based MAX phase particles

Abstract

<p>Two-dimensional carbides/nitrides, typically called MXenes, are an emerging member of the ever-growing family of two- dimensional materials. The prediction of a ferromagnetic groundstate in chromium-containing MXenes has triggered growing interest...</p>

Extending the Chemistry of Layered Solids and Nanosheets: Chemistry and Structure of MAX Phases, MAB Phases and MXenes

“…DFT calculations showed that the formation of Cr and Cr 3 C 2 has a lower reaction energy than the MXene formation and therefore these products form instead of an MXene. This was found in accordance with experimental results [272] . Experimentally, Cr 2 AlC on its own has been exfoliated to an MXene by fluoride free methods in the past.…”

“…This was found in accordance with experimental results. [272] Experimentally, Cr 2 AlC on its own has been exfoliated to an MXene by fluoride free methods in the past. These methods were electrochemical exfoliation [273] as well as the exfoliation by a mixture of FeCl 3 and tartaric acid.…”

Emerging MXene‐Based Memristors for In‐Memory, Neuromorphic Computing, and Logic Operation

“…As shown in Figure 2c, more than 20 kinds of MXenes with M n+1 X n T x (n = 1-4) structures have been reported to date. Currently, the established MXene series include M 2 X (Ti 2 CT x , [93] Ti 2 NT x , [89,94] V 2 CT x , [95][96][97] V 2 NT x , [91] Nb 2 CT x , [98][99][100] Ta 2 CT x , [101] Mo 2 CT x , [102,103] Cr 2 CT x [104,105] ), M 3 X 2 (Cr 2 TiC 2 T x , [106] Mo 2 ScC 2 T x , [106,107] Mo 2 TiC 2 T x , [106,108] Ti 3 CNT x , [109,110] Hf 3 C 2 T x , [111] Ti 3 C 2 T x , [94,112,113] Zr 3 C 2 T x [114] ), M 4 X 3 (Mo 2 Ti 2 C 3 T x , [108] Ta 4 C 3 T x , [115] V 4 C 3 T x , [116,117] Nb 4 C 3 T x , [118] Ti 4 N 3 T x [88] ), and M 5 X 4 (Mo 4 VC 4 T x [119] ). More MXene materials are expected to be exfoliated from the MAX phases in the future.…”

MXenes for Sulfur‐Based Batteries

“…During the etching process, the surface of Ti 3 C 2 could be easily functionalized with ‐OH, ‐O, and ‐F groups, resulting in T‐terminated Ti 3 C 2 T x with hydrophilic nature. By optimizing the reaction temperature, reaction time (from several hours to several days), HF concentration, and introducing new delamination method, various MXenes have been obtained, including Ti 2 CT x , [ 28 ] V 2 CT x , [ 29 ] Nb 2 CT x , [ 29a ] Cr 2 CT x , [ 30 ] Mo 1.33 Y (0.27–0.67) CT x , [ 31 ] Ti y Nb 2− y CT x , [ 28 ] Nb y V 2− y CT x , [ 32 ] (Ti 0.5 ,V 0.5 ) 2 CT x , [ 33 ] Mo 1.33 CT x , [ 31,34 ] W 1.33 CT x , [ 35 ] Nb 1.33 CT x , [ 36 ] Mo 2 CT x , [ 37 ] Ti 3 C 2 T x , [ 7a,28,32,38 ] Ti 3 CNT x , [ 28,32 ] Mo 2 TiC 2 T x , [ 32,39 ] Mo 2 ScC 2 T x , [ 40 ] (V 0.5 Cr 0.5 ) 3 C 2 T x , [ 28 ] Zr 3 C 2 T x , [ 41 ] Hf 3 C 2 T x , [ 42 ] Ta 4 C 3 T x , [ 28 ] V 4 C 3 T x , [ 43 ] Nb 4 C 3 T x , [ 32,44 ] Mo 2 Ti 2 C 3 T x , [ 32,39 ] Mo 4 VC 4 T x , [ 45 ] etc. For example, in 2013, Gogotsi and co‐workers used 50% HF to etch Ti 3 AlC 2 .…”

“…Based on different “M,” MXenes could be divided into four types, [ 66 ] as shown in Figure 7 . The first one is mono‐transition metal MXenes, which is the most common type, including Ti 2 C, [ 28,32,58a–c,59a,62 ] Ti 2 N, [ 52,58a ] Nb 2 C, [ 29a,58c ] V 2 C, [ 29 ] V 2 N, [ 54 ] Cr 2 C, [ 30,59b ] Ta 2 C, [ 58b ] Mo 2 C, [ 37,67 ] Ti 3 C 2 , [ 27,50b,68 ] Zr 3 C 2 , [ 41 ] Hf 3 C 2 , [ 42 ] Ta 4 C 3 , [ 28 ] Nb 4 C 3 , [ 44 ] V 4 C 3 , [ 69 ] Ti 4 N 3 [ 57 ] and so on. The second type is randomly arranged double‐M MXenes, including (Ti,Nb) 2 C, [ 28 ] (Cr,V) 3 C 2 , [ 28 ] (Nb,V) 2 C, [ 32 ] (Nb,Ti) 4 C 3 , [ 56 ] (Nb,Zr) 4 C 3 , [ 56 ] (Mo,V) 4 C 3 , [ 70 ] (Mo,V) 5 C 4 , [ 45 ] and so on.…”