Synthesis and Structural and Electrochemical Characterization of Carbon Fiber/MnO2 Composites for Hydrogen Storage and Electrochemical Sensing

Hydrogen, as an alternative energy carrier, presents significant prospects for the transition to more environmentally friendly energy solutions. However, its efficient and safe storage remains a challenge, as materials with high adsorbent capacity and long-term storage capability are required. This study focuses on the synthesis and characterization of a composite material comprising carbon fiber and manganese dioxide (MnO2/CFs), for the purpose of hydrogen storage. Carbon fiber was chosen as the basis for the composition of the composite material due to its large active surface area and its excellent mechanical, thermal, and electrochemical properties. The deposition of MnO2 on the surface of carbon fibers took place through two different synthetic pathways: electrochemical deposition and chemical synthesis under different conditions. The electrochemical method enabled the production of a greater amount of oxide with optimized structural and chemical properties, whereas the chemical method was simpler but required more time to achieve comparable or lower-capacity performance. Elemental analysis of the electrochemically produced composites showcased an average of 40.5 ± 0.05 wt% Mn presence, which is an indicator of the quantity of MnO2 on the surface responsible for hydrogen storage, while the chemically produced composites showcased an average of 7.6 ± 0.05 wt% Mn presence. Manganese oxide’s high specific capacity and reversible redox reaction participation make it suitable for hydrogen storage applications. The obtained results of the hydrogenated samples through physicochemical characterization indicated the formation of the MnOOH intermediate. Regarding these findings it may be remarked that carbon fiber/MnO2 composites are promising candidates for hydrogen storage technologies. Finally, the fabricated carbon fiber/MnO2 composites were applied successfully as working electrodes for analysis of the [Fe(CN)6]3−/4− redox system in aqueous KCl solutions.