Emerging Materials for Water-Enabled Electricity Generation

Water is one of the most abundant natural resources on Earth, which has attracted huge research interest in the field of energy harvesting and conversion, because of its environmental friendliness and easy access. Through precise regulation of functional materials and elaborate design of the solid/liquid interface, the interactions between water molecules and functional materials enable the generation of considerable electricity, giving researchers an alternative to extract renewable energy from water. In this Perspective, we will systematically discuss the water-enabled electricity generation (WEG) technologies, based on the interactions between functional materials and water. We mainly classify the WEGs into three types: mechanical-to-electric WEG, thermal-to-electric WEG, and chemical-to-electric WEG, according to the energy source of input water and the mode of energy conversion. For each type of WEG, the basic working principles for generating electricity are outlined, accompanied by a summary and comparison of system structures, working types, and performance characteristics. Recent significant progress in terms of the development of functional materials and the design of devices are emphasized. Efficient strategies involving a deep understanding of the solid/liquid interface and the structure of electric double layer, kinetics of ions adsorption, migration and diffusion or combination thereof, are also discussed. Then, we survey nascent fields promising to advance the development of WEGs, particularly in the area of self-powered and wearable electronics. The general requirements for developing next-generation functional materials for high-performance WEGs are further concluded, as well as standards for WEG's performance testing. The scientific and technological challenges and opportunities of WEG are finally addressed for future studies and practical applications.