1+1>2: Cotton stalk derived carbon enables interfacial evaporation and photocatalysis for simultaneous desalination and decontamination of coal chemical wastewater

Interfacial solar evaporation is widely used in desalination, but its application in wastewater treatment is limited by secondary contamination of the condensate by volatile organic compounds (VOCs). In this study, a BiOBr@C composite material was prepared by calcining cotton stalk pyrolysis carbon (C) with BiOBr, and a two-dimensional interfacial evaporator (BCF) was fabricated by coating the composite onto filter paper. Under 1 kW m −2 illumination, the evaporator achieved an evaporation rate of 1.94 kg·m −2 ·h −1 for a 20 mg/L phenol solution, while the phenol removal efficiency in the condensate reached 95%, demonstrating the successful coupling of interfacial evaporation and photocatalysis. Mechanistic analysis showed that C enhanced the solar absorption of BiOBr@C and facilitated charge-carrier separation through efficient electron transport. As a result, the catalytic activity of BiOBr@C in the phenol adsorption–degradation process was improved, and the reaction rate was approximately 1.5 times that of pure BiOBr. In addition, compared with the bulk photocatalytic mode, the BCF interfacial catalytic mode exhibited higher stability and stronger resistance to deactivation during cycling and under different environmental conditions. This study provides a new strategy for synergizing interfacial solar evaporation with photocatalysis and offers a promising solution to the secondary contamination of condensate.