In situ Raman analysis of reduced-graphene oxide-based electroactive nanofluids

This study investigates the effect of an applied stationary voltage on the vibrational properties of 1 M H2SO4 and H2SO4-based reduced-graphene oxide (rGO) nanofluids, commonly used as electrolytes in electrochemical cells. Our findings indicate that the energy of the symmetric stretching vibrations of H2SO4 remains unaffected by the electric field. However, a slight deviation toward lower energy and an enhancement of Raman intensity are observed in the asymmetric stretching vibration of H2SO4 due to the applied voltage. Furthermore, the addition of rGO to the base fluid produces a significant redshift in the symmetric stretching bands, indicating that the presence of rGO produces important changes at the macroscopic level in the base fluid. Synchronous and asynchronous maps further uncover the positive correlations between the D and G bands as well as between rGO and the base fluid bands. Specifically, the asynchronous map revealed complex dynamics between the rGO and H2SO4 bands and only positive correlations between H2SO4 bands. These results demonstrate the potential of Raman spectroscopy as a non-invasive technique to systematically study the influence of electric fields on the vibrational properties of fluids and nanofluids, which can ultimately lead to the development of significantly more efficient electrochemical cells.