Symmetry-Breaking-Induced Multifunctionalities of Two-Dimensional Chromium-Based Materials for Nanoelectronics and Clean Energy Conversion
Lei Li, Tao Huang, Kun Liang, Si Yuan, Ji‐Chun Lian, Wei‐Qing Huang, Wangyu Hu, Gui‐Fang Huang
Abstract
Structural symmetry breaking, which could lead to exotic physical properties, plays a crucial role in determining the functions of a system, especially for two-dimensional (2D) materials. Here, we demonstrate that multiple functionalities of 2D chromium-based materials can be achieved by breaking inversion symmetry via replacing $Y$ atoms in one face of pristine $\mathrm{Cr}$Y (Y = $\mathrm{P}$, $\mathrm{As}$, $\mathrm{Sb}$) monolayers with $\mathrm{N}$ atoms, i.e., forming Janus ${\mathrm{Cr}}_{2}\mathrm{N}Y$ monolayers. The functionalities include gapless spin, very low work function, inducing carrier doping, and catalytic activity, which are predominately ascribed to the large intrinsic dipole of Janus ${\mathrm{Cr}}_{2}\mathrm{N}Y$ monolayers, giving them great potential for various applications. Specifically, ${\mathrm{Cr}}_{2}\mathrm{NSb}$ is found to be a spin-gapless semiconductor, ${\mathrm{Cr}}_{2}\mathrm{NP}$ and ${\mathrm{Cr}}_{2}\mathrm{NHPF}$ can simultaneously induce n- and p-type carrier doping for two graphene sheets with different concentrations (forming an intrinsic p-n vertical junction), and ${\mathrm{Cr}}_{2}\mathrm{N}Y$ exhibits excellent electrocatalytic hydrogen-evolution activity, even superior to that of benchmark $\mathrm{Pt}$. The results confirm that breaking symmetry is a promising approach for the rational design of multifunctional 2D materials.