New Two-Dimensional Carbon Sheet for Photocatalytic Water Splitting with High Carrier Mobility and Excellent Mechanical Properties.

Combining first-principles calculations with particle swarm optimization algorithms, we have successfully predicted an innovative two-dimensional carbon structure─the 2D 2 structure. This structure not only passed rigorous tests for kinetic and thermal stability but also demonstrated remarkable stability in air. This structure is originally a semiconductor with a quasi-direct band gap of 2.08 eV, but remarkably, it can be transformed into a direct band gap semiconductor through the application of suitable strain, and its band gap value can be flexibly tuned within the range of 1.85-2.34 eV. It is worth mentioning that regardless of whether strain is applied, the conduction band minimum and valence band maximum of the 2D 2 structure perfectly span the thermodynamic threshold for water splitting, revealing its immense potential in water splitting reactions. Moreover, the structure stands out with a carrier mobility as high as 0.87 × 10 cm·V·s, surpassing numerous renowned 2D materials, including MoS and black phosphorene, indicating its superior performance in electron transport. In the realm of optics, 2D 2 also excels, possessing outstanding light absorption capabilities that provide a solid foundation for the application of optoelectronic devices. Moreover, the structure exhibits exceptional mechanical properties, including a rare negative Poisson's ratio and a significant bulk modulus, which further broaden its application prospects in nanomechanical systems. The 2D 2 nanosheets, with their comprehensive and exceptional properties, have emerged as ideal candidate materials for various nanodevice fields and have paved new avenues for cutting-edge applications, such as photocatalysis.