Atomically engineered triphase nanoreactors for selective hydrogen peroxide photogeneration

Overcoming oxygen (O 2 ) mass transport and active site limitations is key to advancing photocatalytic hydrogen peroxide (H 2 O 2 ) production via the two-electron O 2 reduction reaction (2e − ORR). Here, we design liquid/solid/gas triphase nanoreactors based on Pt single-atom-decorated carbon nitride nanotubes (Pt/CNNT), which synergistically integrate confined O 2 storage, efficient mass transfer, and highly active atomic sites. The hollow nanotube architecture facilitates continuous O 2 delivery, while atomically dispersed Pt sites modulate the electronic structure to enhance O 2 adsorption and *OOH intermediate formation. As a result, the Pt/CNNT nanoreactors exhibit a seven-fold increase in H 2 O 2 yield compared to the bulk CN diphase system, reaching 232 μmol g −1 h −1 with apparent quantum yields of 5.1 % and 4.2 % at 400 and 420 nm, respectively. DFT calculations and electrochemical studies confirm the enhanced 2e − ORR selectivity via a sequential two-step 1e − pathway. This work highlights the power of nanoreactor engineering combined with atomic-level catalytic tuning for efficient and selective photocatalytic H 2 O 2 synthesis. • Carbon nitride nanotube (CNNT) loaded with Pt atoms was synthesized and characterized. • The cavity of CNNT was confirmed to function as O 2 reservoir for H 2 O 2 photogeneration. • The triphase system generates 7-fold H 2 O 2 yield as CN in two-phase system, reaching 232 μmol g −1 h −1 . • Pt atoms modulate the electronic structure to benefit O 2 adsorption and *OOH formation.