Photocatalytic Applications of Two-Dimensional Ti₃C₂ MXenes: A Review

Abstract

Two-dimensional (2D) Ti 3 C 2 MXenes have aroused tremendous attention as frontier materials for energy storage, solar energy conversion, and environmental remediation because they exhibit high elemental abundance in the earth, a unique layered microstructure, abundant surface functional groups, and prominent electrical conductivity and optical properties. The present study summarizes and discusses the most recent advancements in the synthesis methods of Ti 3 C 2 MXenes; the routes of intercalation, exfoliation, and cutting for multilayered Ti 3 C 2 to obtain its delaminated compounds and quantum dots; and their photocatalysis applications. Given the differences of applied Ti 3 C 2 on morphology and size, high-efficiency Ti 3 C 2 -based Schottky junction photocatalysts and its derivative photocatalysts are generalized and discussed. The advantages of Ti 3 C 2 MXenes in synthesizing high-efficiency photocatalysts are analyzed, consisting of electronic acceptor, substrate, light harvesting, cocatalyst, and precursor. Lastly, the lingering challenges and directions for the subsequent Ti 3 C 2 -based photocatalyst development are proposed.

Advances and Promises of 2D MXenes as Cocatalysts for Artificial Photosynthesis

“…According to the density functional theory (DFT) calculations, the Femi level of Ti 3 C 2 MXene is more positive than that of the CB of most typical semiconductors, indicating that it is possible for the photoelectrons migrating from semiconductors to the MXene. [39,84] Therefore, a Schottky junction could be formed at the interface of the MXene/semiconductor composites, by which the reverse migrating of electrons from MXenes to the semiconductor is prevented. As a result, the photogenerated electrons aggregate at the surface of MXenes and participate in the subsequent photocatalytic reactions.…”

Plasmon-enabled N2 photofixation on partially reduced Ti3C2 MXene

“…Though the metallic Ti 3 C 2 is difficult to photogenerate charge carriers, it can serve as an electron acceptor to capture the hot electrons generated by the plasmonic Au nanospheres owing to its superior electrical conductivity. 32 …”

“…51 Despite the broad light absorption, very few charge carriers can be photogenerated and separated in Ti 3 C 2 and r-Ti 3 C 2 . [32][33][34] On the other hand, the efficient photothermal conversion of Ti 3 C 2 MXene can facilitate surface catalytic reactions through the conversion of light to heat to activate the supported catalyst. 52 Unlike common plasmonic Au/semiconductor hybrid photocatalysts, 36,53 the absorption peak from the LSPR band of the Au nanospheres cannot be clearly observed in Ti 3 C 2 /Au or r-Ti 3 C 2 /Au.…”

“…31 Unfortunately, the extremely low Fermi level and metallic nature of Ti 3 C 2 make it a superior electron acceptor, resulting in a poor separation efficiency of photogenerated electrons and holes. 32,33 In addition, the narrow bandgap of Ti 3 C 2 makes N 2 photoreduction difficult. 34 As a result, it has remained challenging to realize N 2 photofixation with sole Ti 3 C 2 .…”

Solar fuels: research and development strategies to accelerate photocatalytic CO2 conversion into hydrocarbon fuels

“…345 In addition to these energy storage applications, they have also been explored as promising photocatalytic materials. [346][347][348][349] The 2D structure of MXenes affords a high surface area and good pore structure, making these materials an excellent choice for enhanced CO 2 adsorption and photocatalytic activity. Moreover, MXenes may serve as efficient cocatalysts in photocatalysis owing to their good electronic conductivity, adjustable bandgap, and strong metallic characteristics.…”