Tin Oxide (SnO₂)-Decorated Reduced Graphene Oxide (rGO)-Based Hydroelectric Cells to Generate Large Current

Nonphotocatalytic water splitting through oxygen-deficient, mesoporous metal oxide design-based hydroelectric cells (HECs) is a well-known phenomenon. To exploit more power from HECs, a metal oxide with more oxygen deficiency is desirable. In this study, oxygen-deficient mesoporous SnO₂ via a sol-gel method and its composites with reduced graphene oxide (rGO) have been presented. Raman spectra of SnO₂-rGO nanocomposites revealed an increase in the oxygen vacancies, while the X-ray diffraction (XRD) pattern confirmed the strain formation in the nanocomposite lattice owing to defect formation. The X-ray photoemission spectroscopy (XPS) results also indicated the presence of oxygen vacancies on the surface of SnO₂, whereas Brunauer-Emmett-Teller (BET) measurements revealed that adding rGO into SnO₂ increased the surface area from 44.54 to 84.00 m² g^-1. The water molecules are chemidissociated on the oxygen-deficient mesoporous surface of the pellet followed by physiodissociation at the mesopores. The redox reaction of the dissociated ions at the Zn anode and the Ag inert cathode produces current in the outer circuit. Interestingly, adding few drops of water into a SnO₂-rGO-based HEC resulted in a short-circuit current of 148 mA with an open-cell voltage of 1.0 V. The maximum power delivered by the SnO₂-rGO-based HEC is 148 mW. The addition of rGO into SnO₂ boosts the peak current remarkably from 68 to 148 mA, which is the highest reported current generated by a hydroelectric cell.