Sulfated nanocellulose (SCNF) and reduced graphene oxide (rGO) films were fabricated through environmentally friendly methods to develop an effective platform for electrochemical applications. The hybrid materials were extensively characterized by FTIR, XRD, Raman spectroscopy, TGA, SEM, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Results showed that incorporating rGO into the SCNF matrix significantly improved the electrical conductivity and structural robustness of the films. FTIR confirmed interactions between sulfate groups on cellulose and residual oxygen-containing groups on rGO, while XRD and Raman analyses indicated reduced crystallinity and increased structural disorder, supporting the successful integration of both phases. XPS further demonstrated that SCNF and rGO form chemical bonds rather than simply mixing, with both components remaining active at the surface—evidence of strong interfacial interactions that contribute to enhanced stability and efficient charge transfer. The 1:5 (rGO:SCNF) composition showed the best electrochemical performance, exhibiting minimal charge-transfer resistance and improved hydrazine oxidation, as reflected by a shift of the anodic peak potential toward lower values. Additionally, functionalization with cobalt porphyrin significantly boosted catalytic activity. Overall, the SCNF:rGO films offer a sustainable and scalable platform for electrochemical sensing and energy-conversion applications, demonstrating excellent adaptability and functional performance.

Developing efficient, stable, and cost-effective electrocatalysts for the oxygen reduction reaction in acidic media remains a critical challenge for advancing technologies like proton exchange membrane fuel cells . This work explores the use of transition metal oxides integrated into a carbon paste matrix as PGM-free alternatives. We synthesized α-Fe2O3, Co3O4, and CoFe2O4 nanoparticles and incorporated them into a composite electrode consisting of multi-walled carbon nanotubes and a N-octylpyridinium hexafluorophosphate ionic liquid binder. Preliminary electrochemical screening by cyclic voltammetry in O2-saturated 0.1 M HClO4 suggested a qualitative activity trend: MWCNTs/IL/ α-Fe2O3 > MWCNTs/IL/CoFe2O4 > MWCNTs/IL/Co3O4 > MWCNTs/IL. The optimized MWCNTs/IL/α-Fe2O3 composite exhibited enhanced ORR performance, with an onset potential of approximately +350 mV vs. RHE and a current density of 11 mA cm-2. Such activity was attributed to a synergistic effect between the well-dispersed α-Fe2O3 nanoparticles and the conductive MWCNTs/IL matrix. Electrochemical impedance spectroscopy (EIS) confirmed this synergy, showing that the α-Fe2O3 composite had a charge-transfer resistance of 1046 Ω, indicating the fastest reaction kinetics among the oxide composites. Furthermore, rotating ring-disk electrode studies demonstrated the catalyst's selectivity, favoring the direct 4-electron pathway to water with minimal hydrogen peroxide production . The α-Fe2O3 system also exhibited operational stability in acid media.