Oxygen self-doping formicary-like electrocatalyst with ultrahigh specific surface area derived from waste pitaya peels for high-yield H2O2 electrosynthesis and efficient electro-Fenton degradation

Abstract

Both sustainable storage of renewable energy using H2O2 as energy carrier and wastewater treatment by electro-Fenton are highly dependent on the efficiency of H2O2 electrosynthesis via 2-electron reduction of O2. Rational design of high-performance and cost-effective electrocatalysts with facile preparation is bear the brunt of scalable H2O2 electrosynthesis. Herein, for the first time, we synthesize a pitaya peel-derived formicary-like electrocatalyst employing facile pyrolysis and KOH activation. At the optimal mass ratio of biochar to KOH (1:3), the electrocatalyst exhibits prominent H2O2 activity and selectivity owing to its rich self-doped oxygen-containing functional groups as well as structural defects and sp3-C bonds serving as reactive sites, rational hierarchical pores boosting mass transfer of reactants and products, and ultrahigh specific surface area facilitating the exposure of reactive sites. Under natural air diffusion, the pitaya peel-derived catalyst-coated cathode achieves surprising H2O2 productivity of 41.6 mg h−1 cm−2 with current efficiency of 65.5% at large current density of 100 mA cm−2, meeting the near-industrial requirements for sustainable H2O2 production. Long-term operation stability at large current and rapid degradation of multiple high-concentration organic pollutants demonstrate tremendous potential of the pitaya peel-derived catalysts for H2O2-based renewable energy storage and environmental remediation.