Computational screening of 2D ternary penta-materials with auxetic properties and efficient photocatalytic CO2 reduction

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Due to unique structural and electronic properties, pentagon-based two-dimensional (2D) materials have captured significant interest in recent years. However, previous studies on these materials have primarily focused on unary and binary systems, with less exploration of ternary pentagonal structures. Herein, we conducted first-principles calculations to evaluate the stability of 122 ternary pentagonal monolayers composed of metals, nitrogen, and chalcogen. We identify six highly stable candidates, including AuNS, CuNTe, GaNS, InNS, SbNS, and SbNSe that meet the criteria for thermodynamic, mechanical, and dynamic stability. Mechanical property analysis reveals that five of these monolayers demonstrate auxetic behavior. Electronic structure calculations show that all candidates are semiconductors with band gaps ranging from 0.12 to 3.42 eV. Specifically, the SbNS and SbNSe monolayers are indirect semiconductors with band gaps of 2.25 and 2.27 eV, respectively. These materials exhibit strong visible light absorption, and potentially serve as exceptional photocatalysts for the reduction of CO2 to CH4 due to the optimal band alignment. The free energy change in the rate-limiting step is even lower than those found in g-C3N4 and MoS2-based systems. Our findings highlight new pentagon-based 2D materials with remarkable electronic, mechanical, and optical properties, making them promising candidates for applications in mechanics and energy conversion.