Curvature and Microenvironment Regulation Enable Robust Seawater Electrochemical Hydrogen Peroxide Synthesis for On‐Site Marine Aquaculture

ABSTRACT Direct electrosynthesis of hydrogen peroxide (H 2 O 2 ) from seawater holds promising prospects for advancing the marine industries. However, the catalysts face severe challenges arising from sluggish oxygen reduction reaction (ORR) kinetics and poor stability under neutral and corrosive chloride ion (Cl − ) conditions of seawater. Herein, we introduce a curvature and microenvironment co‐engineering strategy by constructing a pentagon‐defect‐enriched and interconnected spherical‐architecture carbon (PD/IS‐C). The pentagon defects induce geometric curvature and electronic rearrangement, thus enhancing ORR kinetics, while the interconnected nanospherical channels facilitate mass transfer to create a local alkaline microenvironment that repels Cl − , improving stability. Benefiting from this dual regulation, the PD/IS‐C catalyst achieves outstanding 2e − ORR performance in seawater, delivering an ultrahigh H 2 O 2 yield rate of 67.1 mol g cat −1 h −1 , ~90% Faraday efficiency, and more than 300 h of operational stability. Moreover, the PD/IS‐C electrode achieves the coupling of seawater H 2 O 2 electrosynthesis with real aquaculture practice for the first time, significantly improving the survival rate of fish. This work demonstrates curvature–microenvironment co‐engineering as a powerful design paradigm for robust seawater electrosynthesis and applications.