A Simple, Scalable, Low‐Cost Honeycomb‐Like Carbonized Corncob for Highly Efficient Solar Steam Generation

Abstract Direct solar steam generation (DSSG) is currently one of the most promising desalination methods due to its high energy conversion efficiency. The key element of DSSG is solar thermal conversion materials (STCMs), which absorb incoming solar illumination owing to their excellent solar absorption and convert light to heat. Although many types of STCMs have been applied to DSSG, there are still some existing problems such as complex preparation, high cost, and low energy conversion efficiency. In this work, carbonized corncob, as an example of inexpensive agricultural waste, is prepared as a STCM, which has porous honeycomb‐like pores, and hydrophilic functional groups, ensuring sufficient water transportation. Different pyrolytic temperatures lead to different size pores, content of amorphous carbon, and amount of oxygen functional groups, which affect the water transportation efficiency and light‐to‐heat conversion efficiency. Benefiting from developed pores, 95.7% solar absorption and thick‐hole wall, the carbonized corncob pyrolyzed at 800 °C reaches a solar‐to‐steam conversion efficiency of 86%, and its water evaporation rate is 1.62 kg m –2 h –1 , higher than most biomass reported so far. Using cost‐effective materials and methods to carry out efficient photothermal conversion is of great significance for the realization of practical seawater desalination and sewage treatment.