Molecularly engineered multifunctional Fe-doped ZnO@rGO hybrid nanocomposites with synergistic photocatalytic and pseudocapacitive performance.

A series of molecularly engineered hybrid nanocomposites composed of Fe-doped ZnO nanoparticles uniformly wrapped with reduced graphene oxide (Zn0.85Fe0.15O@rGO) were synthesized with varying volume fractions (0 ≤ vf ≤ 27%) of rGO and their multifunctional physicochemical properties as hybrid nanocomposites for photocatalytic and energy-storage applications were systematically investigated. Structural and optical analyses confirmed the formation of phase-pure wurtzite Zn0.85Fe0.15O, with the composite containing 19.7% volume fraction of rGO (20GZFO), exhibiting the smallest crystallite size (∼77 nm) and an optimized band gap of 2.90 eV. This nanocomposite showed outstanding photocatalytic activity, achieving ∼97.5% degradation of methylene blue under visible light irradiation. This may be attributed to enhanced light absorption, increased surface area, efficient charge separation, and suppressed electron-hole recombination. Moreover, the conductive rGO framework and mixed Fe2+/Fe3+ redox centres enable superior pseudocapacitive behaviour, delivering a high specific capacitance of ∼728 F g-1 at 5 mV s-1 scan rate. Based on the results of spectroscopic investigation by FTIR, a theoretical model of the interfacial interaction of rGO and Zn0.85Fe0.15O has been proposed. The synergistic integration of photocatalytic and electrochemical functionalities highlights Zn0.85Fe0.15O@rGO as a promising high-performance candidate for sustainable environmental remediation as well as advanced energy-storage technologies.