The oxygen reduction reaction (ORR) proceeds via two or four electron pathways, yielding hydrogen peroxide (H2O2) or water, respectively, and is central to energy and environmental technologies. This thesis investigates organic-material/composite catalysts that selectively promote the two-electron ORR in aqueous and alkaline media, and demonstrates their application in photochemical H2O2 generation and electrochemical H2O2 electro-synthesis and energy storage.

The first part presents a scalable, cellulose-based photoactive material: ZnO nanowires grown on paper-like cellulose substrates inspired by papermaking. The resulting ZnO–cellulose “photoactive wallpaper” drives photo-catalytic 2e- ORR under light to produce H2O2, offering a low-energy route for in situ disinfection and pollutant degradation, with clear potential for decentralized environmental remediation.

The second part focuses on the conducting polymer PEDOT (particularly PEDOT:PSS) as an electrocatalyst and ionic conductor for 2e- ORR. We systematically study the roles of primary dopants and secondary (processing) dopants on conductivity, heterogeneous electron transfer, capacitance, and apparent diffusion through the polymer. Secondary doping enhances electrochemically active surface area and mass transport, enabling efficient gas-diffusion electrodes (GDEs) for H2O2 production directly from air. Leveraging PEDOT:PSS’s combined electronic and ionic transport, 3D PEDOT:PSS cathodes enable H2O2 electrosynthesis in pure water, reaching 6.6 mg h-1 cm-2 production at 70% Faradaic efficiency and low energy consumption.

Finally, applying PEDOT:PSS as an air cathode in rechargeable zinc–air batteries (ZAB) demonstrates improved reversibility and kinetics compared with conventional carbon cathodes; a PEDOT:PSS-based ZAB in a near-neutral water-in-salt electrolyte exhibits >70% round-trip efficiency and stable cycling. Together, these studies identify organic catalysts—both electro-catalytic and photocatalytic—that selectively promote 2e- ORR and demonstrate their utility in sustainable, decentralized chemical and energy technologies.