Enhancing 3D/2D interfacial integrity between defect-engineered Mn-SrTiO₃ and rGO for high-efficiency bifunctional...

Growing global energy needs and the expanding clean hydrogen market underscore the urgency of developing sustainable, high-efficiency electrocatalysts for the OER and HER. In this study, we report a strategically engineered 3D/2D hybrid catalyst based on defect-modulated Mn-SrTiO₃ (MSTO) coupling with reduced graphene oxide (rGO) to promote interfacial charge transport and bifunctional water-splitting performance. MSTO nanostructures (NSs) were fabricated via a sol-gel approach, and their intimate integration with rGO was achieved through a solvothermal process, yielding Mn-SrTiO₃/rGO nanocomposites (MSTG NCs). XRD confirmed that Mn ions were substitutionally incorporated into the STO lattice without forming secondary phases, while rGO incorporation optimized lattice strain and oxygen-vacancy generation. Spectroscopic analyses revealed band-gap narrowing, suppressed charge recombination, enhanced defect density, and strong interfacial coupling in MSTG2 (20 wt% rGO). TEM verified uniform dispersion and robust MSTO-rGO interfaces conducive to fast carrier dynamics. Electrochemical evaluations identified MSTG2 as the most efficient bifunctional catalyst, exhibiting the lowest overpotentials and Tafel slopes for both the HER (-0.348 V, 58 mV dec^-1) and the OER (1.672 V, 152 mV dec^-1), along with the largest electrochemically active surface area, improved redox kinetics, and significantly reduced charge-transfer resistance. Stability assessments confirmed long-term durability under alkaline conditions. The synergistic combination of Mn-induced defect engineering and rGO-mediated conductive pathways enables rapid electron transfer, high active-site utilization, and enhanced structural stability. This work highlights the critical importance of optimizing 3D/2D interfacial integrity in oxide-carbon hybrids and positions MSTG NCs as a viable, scalable, and highly active bifunctional catalyst for next-generation electrochemical water-splitting systems.