Hybrid nanostructures of transition metal oxides on vertical graphene for enhanced electrochemical performance

Transition metal oxide (TMO) nanostructures have attracted particular interest due to their multifunctionality, ranging from biomedical devices to electrochemical sensors for wastewater treatment in the textile industry, food processing and packaging, energy storage systems, catalysts, and solar cells. Among the different materials studied, In2O3 nanostructures have the advantages of remarkable physicochemical properties, high specific surface area, high surface-to-volume ratio, substantial chemical and environmental stability, and high electron mobility. Over the years, different substrates have been studied for the deposition of TMO thin films to meet the requirements of the targeted fields. In the present work, In₂O₃ nanostructures were obtained by chemical synthesis, and the process conditions and thermal treatment parameters were controlled, with these factors being considered the determining factors with effects on particle size and morphology. To ensure that the oxide nanostructures were compatible with the substrate of interest, graphene hydrophilization was performed. The next step consisted of dispersion of In₂O₃ powders in different media, drop-casting a suspension of oxide particles on the surface of the vertical graphene substrate, and evaporation of the solvent by heat treatment. The analytical methods used indicate a slight tendency of the particles to agglomerate at the surface but also to penetrate between the graphene sheets. FTIR spectroscopy studies and XRD diffraction measurements were carried out to determine their structure. The surface wettability was determined by measuring the contact angle to confirm the hydrophilicity. Furthermore, the electrochemical activities were investigated by cyclic voltammetry.

Acknowledgments: This work was supported by a grant from the Ministry of Research, Innovation and Digitization, CNCS-UEFISCDI, project number PN-IV-P2-2.1-TE-2023-0417, within PNCDI IV and by the Core Program within the National Research Development and Innovation Plan 2022-2027, project no. 2307.