Hydrothermal treatment of GO-based nanocomposites for energy storage: New insights into the components’ interaction

Abstract

In this study, graphene oxide (GO)-based nanocomposites with 12-tungstophosphoric acid (WPA) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 15 wt.% each, were hydrothermally treated (HTT) at 180 °C for 8 hours to investigate their electrochemical charge storage capabilities. Structural and compositional changes were evaluated via FTIR, XPS, TPD, and LDI-MS, while morphological characteristics were analyzed using SEM and TEM. FTIR confirmed the presence of primary oxygen-containing groups in GO and successful incorporation of modifiers, while the XPS data indicated HTT-induced reduction of these groups, particularly epoxides. TPD revealed an increased desorption of surface functionalities after HTT, especially above 500 °C. SEM showed the evolution of the layered GO morphology into a hierarchically porous matrix, while TEM confirmed nanoscale integration of PTCDA and deposition of WPA nanostructures across the GO surface. Notably, LDI-MS provided complementary insight into the molecular-level interactions. The spectrum of HTT-treated GO/PTCDA displayed distinct Cn and Cn(CH)m cluster distributions compared to untreated GO, with a reduced intensity of OH- ions post-treatment, confirming the reduction of GO surface. Fragment ions characteristic of PTCDA, absent in the spectrum of pure PTCDA, were observed only after HTT. For GO/WPA/PTCDA, LDI-MS revealed fragment ions from both PTCDA and WPA, including characteristic polyoxometalate species at m/z 232–928 and a [W₁₂O₄₁]²⁻ peak at m/z 2862. After 8 hours of HTT, the nanocomposites formed a hierarchical structure resulting in enhanced capacitive behavior. Cyclic voltammetry showed a specific capacitance of ~300 F/g for GO/PTCDA, which is attributed to improved interfacial properties, high electron affinity of PTCDA and suitable morphology. These findings reveal important changes of structure and surface chemistry at the molecular level of GO-based nanocomposite which is of importance for the rational design of GO-based electrodes for high-performance supercapacitors.