Structure Characterization and Application of Graphdiyne in Photocatalytic and Electrocatalytic Reactions

Graphdiyne (GDY) is a new booming carbon material with a highly pi-conjugated structure that consists of sp- and sp(2)-hybridized carbon atoms. Due to the diverse compositions of the carbon atoms, GDYs can be divided into several forms based on their structure and periodicity. Until 2010, gamma-GDY has been successfully synthesized and becomes a new member of the carbon family. Many researchers have subsequently devoted their attention to the study of GDY. Compared to the traditional carbon materials, GDY exhibits a unique carbon network and electronic structure, thereby attracting considerable attention in a variety of fields. With the development of its synthetic chemistry, many types of GDY with different structures have been synthesized and characterized. The characterization of their micromorphology is crucial for studying the synthesis procedure and understanding the properties of GDY materials. At present, the developed method can characterize GDY morphology, crystal structure, and the chemical bonds of the carbon atoms. Specifically, the morphology and thickness of GDY can be evaluated by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The crystal structure can be investigated using X-ray diffraction and high-resolution transmission electron microscopy. The chemical bonding of the carbon atoms can be analyzed by Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, C-13 nuclear magnetic resonance (C-13 NMR), UV-visible (UV-Vis) absorption spectroscopy, etc. However, methods for the rapid and nondestructive characterization of the highly crystalline graphdiyne are still absent, restricting the study of the intrinsic properties of GDY. Due to the unique electronic and porous structure of GDY, it has been the focus of extensive investigations in the field of catalysis. As a result of its favorable electronic structure and good capability for transferring photoexcited electrons and holes, GDY can enhance light absorption and facilitate the separation of photoexcited charge carriers in semiconductors and thereby significantly promote their photocatalytic performance. In addition, GDY can be modified using foreign elements, providing an ideal platform to prepare a highly active catalyst for the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, etc. Furthermore, GDY can be synthesized on arbitrary substrates in a three-dimensional nanosheet array structure, which can provide a large number of channels for the transfer of electrons and a large contact area with the reactant, which is beneficial in electrocatalytic reactions. This review focused on the recent developments in characterization methods as well as the photo and electrocatalysis applications of GDY, and elaborated the opportunities and challenges for the investigation of GDY in the future.