Realization of Low Latent Heat of a Solar Evaporator via Regulating the Water State in Wood Channels.

Solar-driven interfacial evaporation with heat localization is an efficient method for large-scale water purification. However, due to the high latent heat of water evaporation and dilute solar flux (1 kW m-2), the solar steam productivity is low. Here, the latent heat of water evaporation was reduced because of the capillary water state in wood channels. We constructed a wood-based 3D solar evaporator via regulating the hydrophilicity of a surface of burnt wood and adjusting the height of the wood above a water surface. Capillary water was formed in the light absorption layer, resulting in the latent heat decrease from 2444 to 1769 J g-1. A high evaporation rate of 1.93 kg m-2 h-1 under one sun irradiation (1 kW m-2) was achieved. Together with the environmental energy-harvesting ability, the evaporation rate reached 3.91 kg m-2 h-1 (per occupied area), which is among the best values ever reported. More importantly, the 3D solar evaporator works efficiently in a water collection device, yielding 2.2 times more water than that of a common interfacial evaporator.