Interfacial Coupling and Defect Modulation in TiO ₂ /rGO Hybrid Nanosheets for Superior Photocatalytic and Photoelectrochemical Efficiency

This work designs the synthesis of defect-engineered TiO 2 nanosheets (T12 NSs) coupled with reduced graphene oxide (rGO) via a facile polyol method, demonstrating their enhanced performance in Rhodamine B (RhB) dye degradation and photoelectrochemical (PEC) water splitting. The novelty lies in the controlled introduction of oxygen vacancies (O v ’s)/Ti 3+ states and optimized TiO 2 /rGO ratios, which synergistically improve light absorption, charge separation, and catalytic efficiency compared to pristine TiO 2 . Structural analyses (XRD, Raman, TEM) confirmed successful hybridization between defect-rich TiO 2 NSs and conductive rGO sheets, forming a hierarchical nanosheet–nanosheet heterostructure with intimate interfacial contact. Among all compositions, T2G1 (TiO 2:rGO = 2:1) exhibited optimal structural and electronic properties, including enhanced lattice strain, bandgap narrowing (2.68 eV), and increased surface area (186.88 m 2 g –1 ). Spectroscopic studies (photoluminescence (PL), time resolved PL (TRPL), EPR, and XPS) revealed that T2G1 possessed abundant surface and bulk defects, prolonged carrier lifetime (37.8 ns), and effective suppression of recombination through rGO-mediated charge transfer. Photocatalytically, T2G1 achieved a rate constant of 0.0227 min –1 at 93.9%, significantly surpassing that of pristine T12 (0.0072 min –1 ). In PEC studies, T2G1 displayed the highest photocurrent density, lowest overpotentials (0.909 V for the OER, 0.411 V for the HER), and smallest Tafel slopes (73 and 41 mV·dec –1 ), confirming superior redox kinetics and charge transport behavior. Overall, this work establishes an effective strategy for synergistic defect and interface engineering in TiO 2 /rGO hybrids, where oxygen vacancies, Ti 3+ centers, and graphene coupling collectively enhance light harvesting and electron mobility. The optimized T2G1 nanocomposite serves as an efficient and stable material for environmental remediation and solar-driven water splitting, advancing sustainable photocatalytic technologies.