面向二电子氧还原的纳米石墨稳定化合金催化剂制备与构效关系研究

Two electron oxygen reduction reaction (2e ORR) catalyst could convert oxygen to hydrogen peroxide on site, which is very promising for water treatment, energy-saving transformation of chlor-alkali industry, etc. As the conventional 2e ORR catalysts, carbon materials possess low cost and high chemical stability, but also low selectivity and bad activity. A lot of work have been done to enhance the selectivity and activity of carbon materials by modification, however, it generally damages the chemical stability of the catalysts and electrodes. Recently, researchers discover that some metal alloys, such as Pt-Hg, obtain high catalytic activity and excellent selectivity as high as 96%, but meanwhile with high cost, and alloy ingredients tend to run off in the electrochemical reactor. Based on the state of art of 2e ORR catalyst, learning from the intercalation reaction of lithium ion into graphite in lithium ion battery, this project proposes using low-cost and high chemical stable nano graphite (NG) as basis material, high selective and active metal alloys as second component, to synthesize a new NG/MA(metal alloy) catalyst with a sandwich structure which could stabilize and nano-crystallize the metal component and hinder the leaching of the alloy ingredients, moreover, investigating the relationship between the structure, component, morphology of the NG/MA with its catalytic activity, selectivity and stability. Based on the above work, the preparation method of the gas diffusion electrode based on this new catalyst would be investigated. These efforts would lay the foundation of the application of 2e ORR in the related fields.

二电子氧还原电催化剂可将氧原位转化为过氧化氢，在污水处理、氯碱工业节能改造等领域应用前景广阔。常见的二电子氧还原电催化剂—碳材料存在活性和选择性低的问题，对碳材料进行改性在提高其活性或选择性的同时，往往降低了其稳定性。最新研究发现，某些合金（如Pt-Hg）具有超出碳材料数十倍的二电子氧还原活性和高达96%的选择性，但存在合金组分（如Hg）易于流失的问题，且成本偏高。本项目拟以价格低廉、化学稳定性高的纳米石墨为基体，高选择性、高活性的合金为第二组元，借鉴锂离子电池领域锂离子在石墨层中的插入反应，合成一种纳米石墨-合金插层结构二电子氧还原电催化剂，利用石墨层的“包夹”实现合金组分的稳定化、纳米化，研究纳米石墨-合金插层结构电催化剂结构、组成、形貌等与其催化活性、选择性、稳定性的构效关系，在此基础上探索适用于该催化剂的气体扩散电极制备方法，从而为二电子氧还原阴极技术在相关领域的应用奠定基础。

二电子氧还原电催化剂可将氧原位转化为过氧化氢，在污水处理、氯碱工业节能改造以及某型化学激光器原料再生等领域，应用前景广阔。但常见的氧还原催化剂在催化氧还原时，主要以四电子路径为主，其产物为水，发生二电子还原生成的过氧化物也易于在催化剂的作用转变为水，最终结果导致获得的过氧化物浓度非常低，达不到实用化的要求。本项目研制了多种二电子氧还原催化剂，包括XC-72、石墨烯、Au/RGO、Co3O4/C、Pt/Hg-GICs、Pt-Hg/C、纳米石墨、Pt-Co/C、Pd-Au/C催化剂等，利用旋转环盘电极技术对其进行了研究，得到了综合性能较好的二电子氧还原催化剂，实验结果表明Au/RGO选择性可达83.2%，石墨烯二电子选择性可达85.7%。对氧的局域传质进行了研究，在此基础上探索了适用于该二电子氧还原催化剂的气体扩散电极制备方法。设计了不同反应器，进行了氧通过二电子还原制备过氧化物的电解实验，实验中过氧化物产出浓度达到4.575mol/L，与已有文献报道结果（通常低于1mol/L）相比，过氧化物产物浓度得以大幅度提升，满足了某型化学激光器对过氧化物浓度的基本要求，有望应用于某型化学激光器，也为将其应用于污水处理、氯碱工业节能改造等领域打下了较好基础。