Unravelling the 2e^- ORR Pathway through Kinetic Analysis for Sustainable Electrocatalytic Formation of H₂O₂ in Highly...

Hydrogen peroxide (H₂O₂) production via electrocatalytic oxygen reduction reaction (ORR) is considered a sustainable approach in contrast to the conventional anthraquinone-based H₂O₂ synthesis. Improving cathodic stability and the selectivity of electrocatalysts for the 2e^- ORR is still not sufficiently understood for industrial-scale electrosynthesis of H₂O₂. Herein, we report the synthesis of porous carbon from the vacuum residue (VR) of crude oil via controlled pyrolysis and chemical activation, resulting in VR-KOH750 at 750 °C, which exhibits a high surface area at 4200 m² g^-1 and microporosity. VR-KOH750 as an electrocatalyst for ORR exhibits a cathodic peak potential of 0.75 V versus RHE, with high durability and no observable shift in the cathodic peak potential during stability tests. Rotating disk and ring-disk electrode measurements under hydrodynamic conditions were employed to evaluate the electrocatalytic behavior of VR-KOH750 toward the 2e^- ORR, demonstrating a strong preference for the two-electron pathway with an approximately 70.6% hydrogen peroxide (H₂O₂) yield. The kinetic analysis was carried out utilizing the Damjanovic model, further confirming the peroxide pathway. Furthermore, the work also explores how different catalyst loadings and wettabilities affect the intrinsic catalytic activity, selectivity, and overall H₂O₂ yield. The results feature the significance of fine-tuning electrocatalysts to create intrinsic microenvironments and enhance active sites, thereby optimizing OOH* adsorption and ensuring an efficient 2e^- process. The efficient ORR performance under alkaline conditions suggests that highly microporous carbons are promising candidates for sustainable electrocatalytic applications.