催化在现代化工生产中正发挥非常重要的作用.在未来催化甚至会扮演更重要的角色.然而,现有的催化剂制备方法会对空气、水和土地造成污染.这些污染主要来源于催化剂制备过程中会用到的各种有害化学品.而且,现有催化剂制备过程耗时长、耗能高、用水量大.这些都不符合绿色化学原则.因此,开展催化剂绿色制备研究十分必要.这一研究的长远目标是避免或者消除催化剂制备过程每一环节产生的污染,降低每一环节的能耗和物耗,缩短制备时间,减少劳动强度.显然,这并不是一个容易达成的目标.因此,朝着上述长远目标的任何进展,无论是小进展还是大进展,都将有助于最终实现催化剂的绿色制备.我们总结了气体放电冷等离子体在催化剂绿色制备方面的最新进展,特别强调了非氢冷等离子体在催化剂制备中的应用.冷等离子体是一种能在室温附近操作的非平衡等离子体,是对气体施加一定电压(数百至上万伏特;具体电压值取决于气体压力)形成的.冷等离子体制备方法可以在少用或者不用有害化学品的基础上,有效减小催化剂粒径、增加催化剂分散度、提高催化剂和载体的相互作用等.这些改进同时能进一步提高催化剂的活性和稳定性.相对于常规热化学制备催化剂,冷等离子体制备的显著区别在于:冷等离子体在室温或者略高于室温条件下操作,可以有效避免热化学方法存在的缺点.冷等离子体方法利用其富含的高能物质(如电子)快速促进催化剂前驱体分解,从而实现催化剂快速成核.由于低温操作,其晶体生长速度受到限制,催化剂分散性得以提高.研究表明,以非氢等离子体作为电子源的室温电子还原能够有效还原贵金属离子.这个过程中既不需要有害化学还原剂也不需要氢还原.这为以热敏材料和化学不稳定物质作为基底的负载型催化剂制备创造?
Most current catalyst preparation methods cause pollution to air, water and land with the use of hazardous chemicals, lengthy operation time, high energy input and excessive water usage. The development of green catalyst preparation is necessary to prevent and eliminate waste from each step of the catalyst preparation. We summarize recent progress in the application of cold plasmas for green catalyst preparation. Cold plasma preparation can reduce the catalyst size, improve the dispersion and enhance catalyst-support interaction with the use of less or no hazardous chemicals. These improvements also lead to the enhancement of catalyst activity and stability. An alternative room temperature electron reduction with a non-hydrogen plasma as an electron source was developed for the reduction of noble metal ions in which no hazardous chemical reducing agent or hydrogen was needed. This creates many opportunities for the development of supported catalysts with heat sensitive substrates, including metal organic frameworks (MOFs), covalent organic framework(COFs), high surface area carbon, peptide, DNA, proteins and others. A novel floating metal catalyst on a water(or solution) surface has been established. Template removal using low temperature cold plasmas also leads to the formation of high surface area porous materials with characteristics that are normally only obtainable with high temperature calcination, but sintering can be avoided. Micro combustion has been developed for the removal of carbon template using cold plasma. This is promising for preparing many structured oxides in a simple way with no use of auxiliary chemicals. Many opportunities exist for the use of cold plasmas to make multi-metallic oxides. Some future development ideas are addressed.