An efficient electrocatalytic in-situ hydrogen peroxide generation for ballast water treatment with oxygen groups.

The in-situ electrochemical production of hydrogen peroxide (HO) offers a promising approach for ballast water treatment. However, further advancements are required to develop electrocatalysts capable of achieving efficient HO generation in seawater environments. Herein, we synthesized two-dimensional lamellated porous carbon nanosheets enriched with oxygen functional groups, which exhibited exceptional performance in HO electrosynthesis. The carbon nanosheet electrocatalysts demonstrated high selectivity for HO production, reaching 90 % at 0.33 V vs. RHE under neutral conditions. Maximum yields were achieved at 2238 mmol g h at -0.5 V in an H-type electrolysis cell and 3681 mmol g h at a current density of 150 mA cm in a flow cell, with Faraday efficiencies exceeding 70 %. Notably, a continuous 9-hour electrosynthesis test produced a high cumulative HO concentration of 1.2 wt% at a current density of 100 mA cm, highlighting the stability and scalability of carbon nanosheets. The outstanding performance of carbon nanosheets is attributed to the abundant basal plane C-O-C group, which provide optimal *OOH binding energy and minimal overpotential. Additionally, the in-situ generated HO from the electrocatalytic system achieved complete sterilization within 60 min against Escherichia coli and several marine bacterial strains isolated from seawater. Furthermore, treatment of real seawater with HO significantly altered the bacterial population abundance at both the phylum and genus levels, highlighting its effectiveness in microbial control. This study presents a high-performance electrocatalytic system for ballast water treatment, offering both scalability and environmental sustainability.