With the growing development of modern society, the demand for freshwater is increasing. Although three‐quarters of the earth's surface is covered by water, less than 3% of it is available for plants, animals, and human life activities. Even so, fresh water is unevenly distributed across the planet, resulting in inadequate water supplies in many areas. It is supposed by the World Health Organization (WHO) that about half of the world's population will face a lack of freshwater resources by 2050.


As is well known, desalination from seawater is one of the most important methods to solve the shortage of freshwater. Solar energy is safe, low‐cost, and green compared to other energy sources such as wind, tide, and nuclear power. In the early days, seawater was desalinated by concentrating sunlight and heating it to generate water vapor. However, this method often has the disadvantage of low efficiency and has not been widely used.


In recent years, solar‐driven interfacial evaporation has been proposed by researchers as a promising alternative to traditional solar heating evaporation or Reverse Osmosis (RO) technology due to its higher energy conversion efficiency. Currently, a variety of solar thermal conversion materials are used for interfacial evaporation, such as graphene, carbon dots, semiconductors, and plasmonic metal. However, their mass production for practical applications is impeded by costly raw materials, complex preparation processes, and non-biodegradability. Low cost, ease of operation, and high stability are the keys to the broad application of interfacial evaporation materials. Therefore, it has become a hotspot for researchers to design a cheap interfacial evaporation material with a high evaporation rate and facile preparation process.

The consensus that producing BioChar and burying it in the ground prevents carbon dioxide emissions into the atmosphere has led to the opening of an economic niche for "investment houses" that trade in carbon credits, namely: polluting industries can "purchase" carbon credit from BioChar producers or trading platforms and thus "offset" their carbon emissions.