Out-of-Plane Piezoelectricity of V2CXY (X/Y = O, S, Se) MXenes Monolayers for Wearable Devices

Abstract

Due to the characteristics of two-dimensional materials, they have demonstrated unique advantages in fields such as piezoelectric devices. Unfortunately, most piezoelectric materials currently do not simultaneously possess excellent piezoelectric effects and mechanical properties. Since the emergence of MXenes, their excellent electrical conductivity and good dynamic and mechanical stability have garnered widespread attention in the energy storage field. Consequently, MXenes are also considered candidates for piezoelectric materials. In this study, the piezoelectric properties and mechanical stability of V₂CXY (V₂COS, V₂CSO, V₂COSe, V₂CSeO) MXenes monolayers were predicted using first-principles methods based on density functional theory. The results indicate that these four materials exhibit good dynamic, thermodynamic, and mechanical stability. It is noteworthy that due to the structural inversion asymmetry and differences in electronegativity, the structure exhibits strong in-plane piezoelectric effects and excellent out-of-plane piezoelectric effects. In particular, the d₃₃ piezoelectric strain coefficient is 2 to 3 orders of magnitude higher than d₂₂ and d₃₁, with the d₃₃ coefficient of V₂CSO reaching up to 313.01 pm/V. This makes these materials highly promising for potential applications in wearable and piezoelectric devices.