Natural wood with optimal capillary water content and evaporation enthalpy for efficient interfacial solar steam generation

Abstract

Natural wood has garnered significant interest in the field of solar steam generation (SSG), due to its merits of widespread availability, hydrophilicity, and inherent porous structure. However, the limited capillary water content and high evaporation enthalpy of wood hinder the evaporation rates of wood-based SSG. In this study, a sulfonated porous wood with high capillary water content and small evaporation enthalpy was developed for efficient solar evaporation. The relatively hydrophobic lignin and hemicellulose were initially removed to enhance capillary effects, achieving a water absorption rate of 5.2 g g⁻¹. Subsequently, sulfonic acid groups were grafted onto the wood surface to weaken the hydrogen bond interaction between water molecules, and thereby reducing the evaporation enthalpy to 1197 J g⁻¹. Molecular dynamics simulations indicate that the sulfonated wood surface contains abundant hydrogen bonding sites, which thermodynamically enhance the escape behavior of water molecules. As a result, the all-biomass SSG demonstrated an evaporation rate of up to 3.4 kg m⁻² h⁻¹ when combined with bamboo carbon black as a photothermal material, representing the highest evaporation rate for wood-based solar evaporation to date. This work provides an effective strategy for efficient wood-based solar steam generation.