Piezoelectric behavior of single-layer oxidized-MXene for nanogenerators and piezotronics

The broad application prospects of two-dimensional (2D) materials have stimulated considerable interest in exploring their piezoelectric properties. Ti3C2Tx MXene has been predicted to possess highly directional piezoelectric properties, owing to its non-centrosymmetric lattice structure. This study presents the experimental piezo-response of oxidized-MXene, which demonstrates that different atomic structure of oxidized-MXene induces unexpected oscillating piezoelectric performance. The presence of surface-modified groups on the Ti3C2Tx-O MXene breaks the inversion symmetry of the lattice structure, thereby exhibiting strongly enhanced piezoelectric behavior. Specifically, the armchair direction of the Ti3C2Tx-O MXene manifests an inherent current output of 1.15 ± 0.20 nA under the tensile strain of 1.30%, yielding a power density of ∼31.04 mW/m2 and a conversion efficiency of ∼17.4%. These values excess those of previously reported 2D materials. Theoretical calculations have provided insights into the underlying mechanisms of piezoelectric polarizations in the multi-atomic structure of various oxidized-MXenes. The discovery of piezo-oxidized-MXene offers a promising avenue for exploring the potential of MXene in the development of nanodevices and stretchable electronics.