Cai Liang

With the rapid advancement of portable wearable electronics, flexible supercapacitors have ushered in new development opportunities. In recent years, MXene and its composites have demonstrated potential as advanced supercapacitor electrode materials due to their outstanding theoretical capacitance, specific surface area, conductivity, hydrophilicity, and mechanical flexibility. This review traces the development of MXene and summarizes common synthesis strategies, with a focus on the effects of different preparation methods on its structure and properties. Departing from previously reported work, this review draws from the practical requirements of flexible supercapacitors to conduct an in-depth analysis of the key factors influencing the charge storage, rate capability, cycling life, and mechanical flexibility of the devices. It summarizes common design strategies for MXene composites currently used to enhance device performance. Additionally, this study analyzes key challenges facing MXene-based electrode materials, including issues such as self-stacking of layers, insufficient oxidation stability, limited energy density, and structural degradation under complex deformation conditions. Mitigation strategies are summarized, including optimizing synthesis methods and constructing composite systems integrating carbon materials, conducting polymers, and transition metal compounds. Finally, future research directions for MXene in flexible energy storage are explored, emphasizing the need to achieve a balance between performance and manufacturability through synergistic regulation at structural design, interfacial engineering, and device levels. This review aims to provide theoretical guidance for the development of practical MXene-based wearable energy storage devices.

The use of differential pressure energy for green hydrogen and ammonia comes with significant safety challenges. Two zero-emission technical schemes—one based on magnetic coupling transmission and another based on dual magnetic fluid seals—were proposed and designed. The energy performance of both schemes was first analyzed for a DN200 pipe using the DWSIM software (Version 8.6.6). Subsequently, the levelized cost of electricity and the dynamic payback period were evaluated and compared. The results show that the magnetic coupling transmission scheme exhibits relatively low energy efficiency (54.9–61.7%), whereas the scheme based on dual magnetic fluid seals is more complex yet achieves higher energy efficiency (65.8–67.1%). The levelized electricity cost of both schemes under a differential pressure of 0.5 MPa is estimated to be lower than the feed-in tariff of coal-fired power plants in China, and the dynamic payback period is estimated to be less than 5.5 years. Overall, both schemes provide benefits in energy savings and profitability. These schemes warrant further experimental investigation and pilot testing.