Band Gap Regulation with Imino Groups in Graphdiyne: A Promising Photocatalyst for Water-Splitting and CO2 Reduction

In this work, two-dimensional (2D) GDY derivatives with the imino groups were investigated with the aid of density functional theory (DFT) calculations. Their structural stabilities were carefully verified. The geometric configurations and mechanical properties of the related systems as well as some typical reference systems were introduced and discussed. At the G0W0 level, the band gaps of the related systems with imino groups are in the range of 1.50–2.20 eV, which are optimal for visible light absorption. Their band edges are more dispersive than those in the other existing GDY derivatives (e.g., F-, H-, and CN-GDYs), leading to their outstanding charge carrier mobilities. Moreover, their band edge arrangements imply the photocatalytic abilities for the complete water-splitting reaction and CO2 reduction. The substitution with imino groups is an effective way to enhance the solar energy harvesting efficiency of the GDY system and its derivatives.