冷等离子体强化制备金属催化剂研究进展

冷等离子体属于非热平衡等离子体，具有较高的电子能量和较低的气体温度，是一种制备金属催化剂的绿色新方法.等离子体强化制备金属催化剂包含复杂的物理和化学多相反应.一方面，等离子体提供的高活性环境不但可以加速化学反应，使反应时间从数小时缩短至数分钟，还可以使热力学或者动力学上不可行的反应发生，实现非常规制备；另一方面，等离子体强化制备过程中，在介观尺度上等离子体对相接触行为的影响，可使获得的金属催化剂结构区别于传统方法制备的催化剂.本综述总结了冷等离子体制备金属催化剂的反应器结构、物理化学机理、获得金属催化剂的结构特性、制备面临的挑战，并对未来发展进行了展望.重点阐述了冷等离子体反应器、制备机制及其对金属催化剂结构和性能的影响.

Research progress of metal catalysts enhanced synthesized by cold plasma

Cold plasma is a kind of non-thermal plasma, and characterized by high electron temperature (1-10 eV) and low gas temperature, which can be close to room temperature. It has been proved to be a fast, facile and environmentally friendly new method for synthesizing supported metal catalysts. Enhanced synthesis of metal catalysts by cold plasma consists of complex physical and chemical reactions. On the one hand, the active environment provided by cold plasma, can not only speed up the chemical reactions, shorten the reaction time from a few hours to several minutes, but also realize the kinetically or thermodynamically infeasible chemical reactions to achieve unconventional preparation. On the other hand, the phase contact behavior on a mesoscopic scale is influenced during cold plasma enhanced preparation, thereby the metal catalysts with structure different from that synthesized by traditional method. This review summarizes the reactor structure, physical and chemical mechanism for synthesizing metal catalysts by cold plasma, as well as the structure characteristics of the obtained metal catalysts. According to the working pressure, cold plasma can be categorized into low-pressure (LP) cold plasma and atmospheric-pressure (AP) cold plasma. The LP cold plasma is often generated by radio frequency glow discharge or direct current glow discharge, while the AP cold plasma is generally generated by dielectric barrier discharge and AP cold plasma jet. Energetic electrons are deemed to be the reducing agents for LP cold plasma. However, due to the frequent collisions among the electrons and gas molecules at atmospheric pressure, the electron energy in AP cold plasma is not high enough to reduce the metal ions directly. Therefore, hydrogen-containing gases are often adopted to generate active hydrogen species to reduce the metal ions. The process of synthesizing the metal catalysts by using the cold plasma is a fast, low-temperature process, and in the preparation process there exists a strong Coulomb repulsion. Therefore, metal catalysts with small size and high dispersion of metal nanoparticles, strong metal-support interaction, as well as specific metal structures (alloying degree and crystallinity) and modified supports can be obtained. Correspondingly, metal catalysts with high catalytic activity and stability can be synthesized. In addition, the challenges of preparing the cold plasma are discussed, and the future development is also prospected.