Spontaneous Phase Transition and Multistage Interfacial Mechanical Friction of Liquid Metals Induced CO₂ Reduction at Room Temperature

Abstract Excessive emissions of carbon dioxide (CO 2 ) have caused the greenhouse effect and environmental crisis. Therefore, the carbon reduction and negative carbon technologies are particularly important. Among these, the negative carbon technologies that convert CO 2 into carbon materials or carbon‐based chemicals for reuse have attracted significant attention. However, the strong double covalent bonds make the CO 2 conversion usually require harsh conditions, complex processes, and high energy consumption. Gallium‐based liquid metals (LMs) are the functional materials with both metallic and liquid properties, exhibiting a unique liquid‐phase structure and diverse surface characteristics. Herein, a strategy for reducing CO 2 is proposed to carbon materials by utilizing the spontaneous phase transition and mechanical friction of liquid metals. The gallium (Ga) and indium (In) particles are mixed and exposed to CO 2 , the contact interface of metal particles spontaneously transforms into liquid metals. The system has multistage interfaces, including Ga/In, Ga/eGaIn, and In/eGaIn, capable of generating triboelectrification upon mechanical stimulation, leading to charge transfer. The high electric field generated by friction at the contact interface directly reduces CO 2 to carbon materials at room temperature. The carbon materials cover the surface of eGaIn and can be directly stripped for used as fuel, or industrial applications.