Design of expanded graphite/poly (vinyl alcohol) hierarchically porous carbon foam by a controllable vacuum foaming strategy for efficient solar evaporation

Abstract

Porous carbon-based evaporators with high light absorption, flexible heat management, and efficient water supply are highly desired in solar water evaporation. However, exploring a facile and powerful strategy to prepare porous carbon-based evaporators remains challenging. In this study, we develop an expanded graphite (EG) and polyvinyl alcohol (PVA) hierarchically porous carbon foam (EG/PVA foam) through a controllable vacuum foaming strategy for solar water evaporation. Owing to high light absorption, low thermal conductivity, efficient water transport, and ample evaporation surface, the optimized EG/PVA foam achieves an evaporation rate of ∼3.10 kg m−2 h−1 with an efficiency of ∼90.75% under one sun irradiation (1 kW m−2). Gratifyingly, the EG/PVA foam enables sufficient vapor diffusion and enhances passive cooling by air convection, thereby achieving a high evaporation rate of ∼8.20 kg m−2 h−1 (wind speed of 3 m s−1). Furthermore, the EG/PVA foam also displays excellent desalination and purification performances with good structural stability, showing considerable promise in practical applications. This work provides a promising path to produce porous carbon-based evaporator for high performance solar water evaporation.