Materials, fundamentals, and technologies of liquid metals toward carbon neutrality

Carbon-neutral technologies are critical to ensure a stable future climate. Currently, low-melting-point liquid metals are emerging rapidly as important energy materials with significant potential to contribute to carbon neutrality. The advantages of gallium- and bismuth-based liquid metals, such as their high fluidity, low melting point, high thermal/electrical conductivity, unique chemical properties, non-flammability, and nontoxic characteristics, render them highly attractive for the development of advanced carbon-neutral technologies. Although their significance in both academia and industry has increased gradually, to the best of our knowledge, a systematic monograph of liquid-metal materials, mechanisms, and technologies toward carbon neutrality is not yet available. Therefore, we presented a comprehensive review of low-melting-point liquid metals for carbon neutrality. First, liquid-metal materials, including fluids, pastes, solids, and their composites were introduced. Subsequently, the mechanisms of liquid-metal technologies used to achieve carbon neutrality were interpreted. Finally, typical liquid-metal applications of carbon neutrality in the power, industry, transport, and building sectors were presented. Both the fundamental mechanisms and promising technologies were elaborated upon, and the critical assessment criteria for carbon-neutral technologies were discussed. The scientific and technical challenges and future perspectives in these areas were also highlighted.