This review highlights recent advances of MXenes and their composites in the environment-related applications including catalysis, water purification and sensors.

Graphene has intrigued the science community by many unique properties not found in conventional materials. In particular, it is the strongest two-dimensional material ever measured, being able to sustain reversible tensile elastic strain larger than 20%, which yields an interesting possibility to tune the properties of graphene by strain and thus opens a new field called “straintronics”. In this article, the current progress in the strain engineering of graphene is reviewed. We first summarize the strain effects on the electronic structure and Raman spectra of graphene. We then highlight the electron–phonon coupling greatly enhanced by the biaxial strain and the strong pseudomagnetic field induced by the non-uniform strain with specific distribution. Finally, the potential application of strain-engineering in the self-assembly of foreign atoms on the graphene surface is also discussed. Given the short history of graphene straintronics research, the current progress has been notable, and many further advances in this field are expected.

Two-dimensional (2D) transition metal carbides/nitrides M _n+1 X _n labeled as MXenes are attracting increasing interest due to promising applications as Li-ion battery anodes and hybrid electro-chemical capacitors.

Graphene has exhibited a wealth of fascinating properties, but is also known not to be a superconductor. Remarkably, we show that graphene can be made a conventional Bardeen-Cooper-Schrieffer superconductor by the combined effect of charge doping and tensile strain. While the effect of doping obviously enlarges the Fermi surface, the effect of strain profoundly increases the electron-phonon coupling. At the experimental accessible doping ($$\sim${}4\ifmmode\times\else\texttimes\fi{}{10}^{14}\text{ }\text{ }{\mathrm{cm}}^{-2}$) and strain ($$\sim${}16%$) levels, the superconducting critical temperature ${T}_{c}$ is estimated to be as high as $$\sim${}30\text{ }\text{ }\mathrm{K}$, the highest for a single-element material above the liquid hydrogen temperature.