碳钢表面原位构筑结构功能一体化微纳嵌套孔膜层及其降解苯酚机制研究

The advantages of low cost and various valence of iron make it draw great attentions as environmental catalytic materials. However, it is seldom reported on the structural-functional integration of the iron-based environmental catalytic materials. To resolve the easily broken off and fragile defects of supported catalyst powders, the proposed project will in-situ fabricate high adhesive strength, impact resistant and porous coating with high mechanical property by liquid plasma electrolytic deposition (PED), whose catalytic property is enhanced by the increase of oxygen vacancy and other defects due to the scorification/the “quick-cooling” effect / solidification of the remarkable repeated plasma discharge and in situ doping. By systematically investigating the porous structure and its evolution during PED, the controllable fabrication model with desired structure and morphology for the PED coating is to be proposed. The enhanced adsorption mechanism induced by the oxygen vacancies in the multilevel porous structure is revealed; the relation between the strong oxidant yielding and microstructure, oxygen vacancies as well as the distribution of iron with different valence is found, and the novel ways to increase the efficiency of degrading phenol is explored. Through the optimization design of the overall materials, the structural-functional integral iron-based catalyst with high mechanical properties and catalytic activities will be fabricated. These researches can provide reference to resolve the bottleneck of difficultly coordinating catalytic activities and mechanical properties for the supported catalysts, which also can extend the potential applications in industry of oxidized iron catalysts.

铁廉价易得且价态丰富，使得铁基环境催化材料受到人们广泛关注，但目前关于铁基催化材料的力学性能与催化活性一体化研究鲜有报道。本项目利用液相等离子体电解沉积（PED）技术在碳钢表面原位生长结合强度高、耐冲击的多孔膜层，基于PED技术独有的反复等离子体放电烧熔/液淬/凝固特性并可原位掺杂改性，来增加膜层中氧空位数量提高催化活性，实现结构功能一体化铁基催化材料制备。研究PED过程膜层孔结构演变规律，实现微纳嵌套孔膜层的可控制备。揭示膜层中氧空位对苯酚的吸附增效机制，建立膜层结构、氧空位和铁价态分布与强氧化剂产出的关系，探索提高苯酚降解效率的新途径。通过对材料整体的优化设计，研制出同时具有高力学性能和催化活性的结构功能一体化多级嵌套孔的铁基催化材料，解决负载型催化材料易脱落、破碎等问题。这些研究可解决负载型催化材料力学与催化性能难协调的瓶颈问题，为拓展铁氧化物催化材料的应用领域奠定理论基础。

本项目利用液相等离子体电解沉积（PED）和电化学还原法制备了两大类兼顾力学性能和高催化活性的结构功能一体化负载型铁基催化材料。基于PED技术，工艺参数为j=12A/cm2、t=10min、f=2000Hz在碳钢表面原位生长结合强度高、耐冲击的Fe3O4/FeAl2O4和Fe3O4/SiO2微纳嵌套孔膜层并原位掺杂硫和锆改性，来增加膜层力学性能和固体酸性提高催化活性，PEO膜层的稳定性研究显示连续降解4次后苯酚降解效率无明显降低有良好的力学性性能，研究PED过程膜层孔结构演变规律，实现结构功能一体化铁基催化材料制备；基于电化学还原法制备了枝状零价铁（ZVI）多级结构，提高材料比表面积达41m2/g，通过溶剂热后处理法对枝状铁表面实施可控氧化，添加葡萄糖为碳量子点前驱体，制备了具有碳量子点和氧空位组成的Fe@Fe3O4枝状结构材料，通过增加材料中氧空位数量提高催化活性。为拓展铁氧化物催化材料的应用领域奠定了理论基础。创新性主要成果如下：研究表明硫改性铁基氧化物膜层表面形成Fe-SO42-键，创造了酸性微环境，提高了该膜层的类Fenton催化活性；制得了含有ZrO2的铁基氧化物复合膜层，由于氧化锆具有固体酸特性，发现其在近中性条件下可快速（＜5min）降解苯酚，降解效率达100%；提出了利用乙醇和葡萄糖溶液制备枝状碳量子点负载铁基材料高效异相类芬顿催化剂的方法，催化剂活性高，金属离子溶出小，且将适用pH扩展到中性条件；富含氧空位的碳量子包覆Fe@Fe3O4类芬顿催化剂在中性条件60min可降解99%的苯酚。揭示了催化剂在中性条件下具有良好的催化活性是由于氧空位与H2O和H2O2分子的作用。