Hydrothermal Carbon with Abundant Oxygen-Containing Functional Groups for Photocatalytic H2O2 Generation in Water and Seawater

• • Achieved a H2O2 production rate of 653 μmol/(g·h) in ultrapure water and actual seawater without sacrificial agents, demonstrating dual-medium viability for decentralized H2O2 synthesis. • • Visible-light-driven benzylamine oxidation reached 92% conversion and >99% selectivity, showcasing dual functionality for fine chemical synthesis under mild conditions. • • Surface oxygen-containing functional groups enhance charge separation and shift the conduction band to a more negative potential, directly improving photocatalytic efficiency. • • Ion interference studies revealed that Ca2+ and K+ markedly inhibit H2O2 production, whereas Mg2+ and Na+ have minimal impact, guiding seawater pretreatment strategies.