2D Ti₃C₂T_x MXenes: Visible Black but Infrared White Materials

Abstract

Black inorganic materials with low infrared absorption/emission (or IR white) are rare in nature but highly desired in numerous areas, such as solar–thermal energy harvesting, multispectral camouflage, thermal insulation, and anti‐counterfeiting. Due to the lack of spectral selectivity in intrinsic materials, such counter‐intuitive properties are generally realized by constructing complicated subwavelength metamaterials with costly nanofabrication techniques. Here, the intrinsically low mid‐IR emissivity (down to 10%) of the 2D Ti3C2Tx MXene is reported. Associated with a high solar absorptance (up to 90%), it embraces the best spectral selectivity among the reported intrinsic black solar‐absorbing materials. Its appealing potential in several of the aforementioned areas is experimentally demonstrated. First‐principles calculations reveal that the IR emissivity of MXene relies on both the nanoflake orientations and terminal groups, indicating great tunability. The calculations also suggest more potential low‐emissivity MXenes including Ti2CTx, Nb2CTx, and V2CTx. This work opens the avenue to further exploration of a family of intrinsically low‐emissivity materials with over 70 members.

Thermoplasmonics in Solar Energy Conversion: Materials, Nanostructured Designs, and Applications

“…Low-dimensional materials such as graphene, with gate-tunable SPs in the IR range and very high thermal conductivity, offer new channels for heat transport and active thermal control; [297,298] While 2D MXenes, such as Ti 3 C 2 T x and a large family of members, have demonstrated intrinsically excellent spectral selectivity and photothermal conversion, which can avoid costly post-nanofabrication process and is quite promising for solar thermal applications. [299] For structural designs, bionics may provide inspiration for revolutionary innovations. Nanofabrication techniques will continue to play a key role in order to realize all these elaborated designs.…”

Solar Selective Absorber for Emerging Sustainable Applications

“…Huang's group reported an 2D Ti 3 C 2 T x MXene material that appears black in visible but white in infrared. [ 40 ] The Ti 3 C 2 T x MXene film was prepared by simple and scalable vacuum filtration technology with 90% solar absorptivity and 10% low infrared emissivity, surpassing the intrinsic materials with the highest selective solar absorption reported so far ( Figure ). Moreover, the as‐prepared Ti 3 C 2 T x MXene is free‐standing, and is suitable for various substrates, including porous and rough surfaces, which show a wider range of applications than conventional SSACs.…”

“…e) IR photographs of the word "HKUST" on hot plates. Reproduced with permission [40]. Copyright 2021, Wiley-VCH GmbH.…”

Combined Experimental and DFT Study on 2D MoSe2 toward Low Infrared Emissivity

“…To our best knowledge, very few works have been heretofore reported on 2DMs of low infrared emissivity. Ultrathin layered double hydroxides (LDHs) [25] and transition metal carbides and/or nitrides (MXenes) [26] have been used as low infrared emissivity materials primarily because of their metallic conductivity arising from the interlayer anions (CO 3 2− , CH 3 COO − , and NO 3 − ) and the terminating functional groups (OH, O, and F). However, the metallic conductivity means a poor impedance matching with air, which would inevitably result in serious radar reflection rather than absorption.…”