Triphase interface engineering in bilayer aerogels for highly efficient water evaporation and photothermal-photocatalytic hydrogen peroxide production.

Abstract

Solar-driven photocatalytic oxygen reduction offers a sustainable route for hydrogen peroxide (H₂O₂) production. However, this process is often limited by the high energy barrier for hydrogen extraction from water, low oxygen solubility and diffusion, and poor selectivity for the two-electron oxygen reduction reaction (ORR), especially under alkaline conditions. Herein, we reported a synergistic photothermal-photocatalytic bilayer aerogel constructed with konjac glucomannan to integrate a photothermal lower layer of reduced graphene oxide (rGO) and a catalytic upper layer of keto-form anthraquinone covalent organic framework (Kf-AQ-COF). Owing to its hydrophobic mesoporous structure, the bilayer aerogel forms a robust gas-liquid-solid triphase interface on a porous substrate. Under alkaline conditions, the hydroxide clusters adsorbed onto ketone moieties can drive the anthraquinone-anthrahydroquinone cycle of Kf-AQ-COF for enabling electron transfer and H₂O₂ production. Meanwhile, the underlying rGO layer functions primarily as a localized photothermal converter and lightweight structural matrix, raising the interfacial temperature to accelerate reaction kinetics and driving rapid vapor escape without altering the intrinsic band structure of the top photocatalyst. As a result, this photothermal-synergistic triphase interface achieves an H₂O₂ production rate of 15.0 mmol m^-2∙h^-1 under air without sacrificial agents within 60 min, which is 1.43 times that of the conventional solid-liquid diphase system. This work demonstrates a new photocatalytic strategy integrating molecular reaction regulation with interfacial engineering.