Bio-inspired synthesis of Co3O4 and NiO nanoparticles for electrocatalytic H2O2 generation and sensing

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Environment friendly reagent Hydrogen peroxide (H2O2) has wide applications in chemical synthesis, food, clinical, biological, and environmental processes. One of the common applications of H2O2 is its use as a precursor for the hydroxyl radicals (•OH) formation in the advanced oxidation processes (AOPs) for the wastewater treatment. Therefore, H2O2 electrogeneration is usually carried out through the reduction of dissolved O2 (DO) in an acidic solution at a low cathodic potential. The present study comprises of three parts.The first part of this work is undertaken to investigate on H2O2 decomposition over a broad range of its concentration which is typically employed in water treatment. Various parameter such as pH and reaction temperature and also trace metals (Na+, Ca2+, Ni2+, Co2+, Cu2+, etc) effect H2O2 decomposition. H2O2 became essentially unstable at a higher pH in the presence of these trace metal ions except Co2+ and Ni2+ due to low catalytic effect. This work also focused on the role of common supporting electrolytes (SEs) in the electro-chemical inertness of Ti-based materials employed for the anodic (direct) oxidation coupled with H2O2 electrogeneration at the graphite cathode for the concurrent decomposition of organic contaminants. It was found that ClO4− corroded TiO2 coated Ti (TiO2–Ti) anode very fast (>60 min), and Ti4+ ions formed a yellow color complex (λmax = 380 nm) with H2O2. The influence of Cl–, NO3−, and SO42− was insignificant on the stability of TiO2–Ti. The cell current efficiency of H2O2 formation dropped sharply with ClO4− in the case of TiO2–Ti anode. The TiO2–Ti corrosion also reduced the mass transfer co-efficient of DO transport from bulk to the cathode surface because of Ti4+ adsorption on graphite cathode.
Supervisor: Animes K Golder