Two-dimensional Janus chalcogenides: candidates for efficient photocatalysts and piezoelectric materials

Abstract

With the continuous consumption of fossil fuels, the depletion of energy will seriously affect sustainable development. Photocatalytic water splitting to produce hydrogen is an effective way to solve the global energy and environmental crisis at present. Screening high efficiency photocatalysts is the key step in the preparation of hydrogen by photocatalytic water splitting. Based on first-principles calculations, we have designed a family of two-dimensional Janus MNXY₂ (N/M = Al, Ga, In, X/Y = S, Se, Te; M ≠ N, X ≠ Y) monolayers and studied the photocatalytic and piezoelectric properties, in which 26 kinds of materials have been selected due to their energy, mechanical, kinetic and thermodynamic stability. The electronic, photocatalytic and piezoelectric properties of stable materials have been studied. It is found that 19/23 among the stable materials are suitable candidates for photocatalyst/piezoelectric materials. It is worth noting that the selected photocatalysts have a high solar-to-hydrogen energy conversion efficiency of 39.60%, a strong visible absorption intensity (up to 7.74 × 10⁵ cm⁻¹), a wide range of light absorption (infrared to ultraviolet), a high carrier mobility (up to 5 × 10⁴ cm² V⁻¹ s⁻¹) and sufficient driving force to stimulate the reaction. In addition, all piezoelectric materials have strong in-plane and out-of-plane piezoelectric responses. This study provides the potential candidates for photocatalyst and piezoelectric materials, which is of great significance for solving energy problems in the future.