Graphdiyne-Based Electrochemical Emissivity Modulator

Electrically controlling the emissivity provides a dynamic, precise, and low-energy-consuming solution for thermal radiation manipulation. The adjustable bandgap, abundant pores, physical stability, and electrochemical activity mean that graphdiyne (GDY) has great potential in electrically emissivity regulation. In this study, a GDY nanowall was successfully synthesized through a cross-coupling reaction with a controlled monomer concentration. Besides the morphology and microstructure characterizations, the intrinsic integrated emissivity in the wavelength of 2–20 μm was determined to be 0.66. Afterward, GDY composited with graphene was utilized as the electrode to fabricate an electrochemical device and emissivity modulator, with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide serving as the electrolyte. Interestingly, the GDY-based modulator demonstrated a unique capacity to modulate emissivity under a negative voltage, unlike pure graphene and other materials that can only regulate emissivity under a positive voltage. To explore the dynamic control mechanism of GDY, an in situ Raman characterization was performed, which revealed a considerable redshift and decrease in the intensity of the characteristic alkyne peaks. We proposed that the novel emissivity tuneability of GDY is caused by the cation-induced changes in the alkyne bond. Alkyne bonds transform into alkene bonds by coordinating with 1-ethyl-3-methylimidazolium cations in the presence of an electrical field, resulting in an energy level change and a change in the optical properties of GDY. These discoveries may open the way for the application of GDY in thermal radiation control and the study of molecular-scale active materials in electro-optical modulation.