Ti₃C₂: An Ideal Co‐catalyst?

Abstract

How 2D Ti3C2 enhances photocatalytic efficiency remains unclear. Now, it is shown that it is graphene quantum dots (GQDs) derived from Ti3C2, rather than 2D Ti3C2 itself, that play the role of co‐catalyst for La2Ti2O7/Ti3C2 (LTC) composites during the photocatalytic reaction. After modification of Ti3C2 derivatives, the photocatalytic efficiency of La2Ti2O7 is enhanced 16 times over pure La2Ti2O7. Solid‐state NMR, Raman, and HRTEM results confirm the existence of GQDs in Ti3C2 and LTC composites. The GQDs are formed during the chemical change from Ti3AlC2 to Ti3C2 via HF etching, as Ti atoms are removed and unsaturated carbon bonds are left, which react with each other to form sp2 π‐conjugation GQDs. 2D Ti3C2 is completely oxidized to COx modified TiOx species, causing Ti3C2 to lose its electrical conductivity and the role as co‐catalyst. GQDs largely suppress the photogenerated charge recombination of La2Ti2O7, as revealed by the photoluminescence (PL) and transient photocurrent.

Ultrathin ZnIn2S4 Nanosheets Anchored on Ti3C2TX MXene for Photocatalytic H2 Evolution

“…MNZIS‐4 shows peaks at 300 cm −1 , 1403 cm −1 , and 1560 cm −1 , corresponding to the stretching modes of ZnIn 2 S 4 , as well as D and G bands of MNs, respectively . The D and G bands are ascribed to graphene quantum dots, derived from the chemical etching process, which could be beneficial for PHE . The enhanced I D / I G value for MNZIS‐4 reveals strong interaction and intensive electron transfer between MNs and ZnIn 2 S 4 …”

Strain Engineering of a MXene/CNT Hierarchical Porous Hollow Microsphere Electrocatalyst for a High‐Efficiency Lithium Polysulfide Conversion Process

“…[18] As acomparison, the proportion of C-Ti-O in the TS-Ti 3 C 2 /CNT is higher than the pristine Ti 3 C 2 ,c orresponding to the formation of heterointerface on the Ti 3 C 2 nanosheet of TS-Ti 3 C 2 /CNT microsphere,i nducing tensile strain formation in TS-Ti 3 C 2 .Inthe high-resolution C1sspectra (Figure 3c), four peaks can be observed, which are located at 282.1 eV, 284.8 eV,2 85.6 eV,a nd 286.6 eV,c orresponding to the chemical bonds of TiÀC, CÀC, CÀO, and C=O, respectively. [19] Thesignificantly intensified C À Cpeak can be ascribed to the successful implantation of CNT tentacle inside TS-Ti 3 C 2 microsphere,c onfirming the chemical constitution of TS-Ti 3 C 2 /CNT.X AS technique was further employed to reveal the structure evolution induced by strain engineering.T he XANES spectrum of TS-Ti 3 C 2 shows the similar shape with Ti 3 C 2 ,confirming their similar structure.Ahigher absorption edge (E 0 )c an be observed in TS-Ti 3 C 2 ,i ndicating the higher valence state of Ti atoms attributed to heterointerface formation (Figure 3d). Theprecise identification of the local environment of these catalysts was achieved by performing the Fourier transform (FT) k 3 -weighted extended X-ray absorption fine structure (EXAFS) spectroscopy (Figure 3e).…”

“… [18] As a comparison, the proportion of C‐Ti‐O in the TS‐Ti 3 C 2 /CNT is higher than the pristine Ti 3 C 2 , corresponding to the formation of heterointerface on the Ti 3 C 2 nanosheet of TS‐Ti 3 C 2 /CNT microsphere, inducing tensile strain formation in TS‐Ti 3 C 2 . In the high‐resolution C 1s spectra (Figure 3 c), four peaks can be observed, which are located at 282.1 eV, 284.8 eV, 285.6 eV, and 286.6 eV, corresponding to the chemical bonds of Ti−C, C−C, C−O, and C=O, respectively [19] . The significantly intensified C−C peak can be ascribed to the successful implantation of CNT tentacle inside TS‐Ti 3 C 2 microsphere, confirming the chemical constitution of TS‐Ti 3 C 2 /CNT.…”

Positioning MXenes in the Photocatalysis Landscape: Competitiveness, Challenges, and Future Perspectives

“…Wang et al found that graphene quantum dots (GQDs) are formed during the chemical change from Ti 3 AlC 2 to Ti 3 C 2 T x via HF etching, as Ti atoms are removed and unsaturated carbon bonds are left, which react with each other to form sp 2 π-conjugation GQDs. [190] On the other hand, 2D Ti 3 C 2 T x is completely oxidized to CO x -modified TiO x species when attempting to prepare La 2 Ti 2 O 7 /Ti 3 C 2 T x composite by a hydrothermal treatment, causing Ti 3 C 2 T x to lose its electrical conductivity and the role as cocatalyst. Although the photoactivity of La 2 Ti 2 O 7 has been improved after introducing Ti 3 C 2 T x derivatives, it suggests that GQDs might be the actual cocatalyst in the study.…”