热释电纳米材料制备及热-电-化学耦合效应室温热催化降解染料

Under illumination, photocatalytic materials create electrons and holes and further generate the strong oxidant free radicals which can degrade dye. Similarly, under temperature alternation, pyroelectric materials can also create electrical charges and further generate the strong oxidant free radicals to degrade dye. The new effect is called “pyro-electro-chemical effect”, which can be considered as the product of pyroelectric effect and electrochemical effect. The new catalytic technology is called “pyrocatalysis”, which is useful in the field of clean-energy and environmental protection, such as cold-hot-alternation-decomposing organic dyes in wastewater at room-temperature, cold-hot-alternation-splitting water for hydrogen production. In this project, we plan to synthesize some typical pyrooelectric LiTaO3, Bi0.5Na0.5TiO3 and Ba0.7Sr0.3TiO3 nanomaterials and systematically study the pyro-electro-chemical effect for the application in pyro-catalytically decomposing organic dyes wastewater under room- temperature cold-hot alternation. We will investigate the dependence of nanoparticle's size and shape, the concentration of electrolyte solution, temperature changing rate and amplitude, pH value, dye types, the addition of catalyst and H2O2, and optimize these parameters and conditions to obtain a high degradation ratio of >90%. The generation process of intermediate product-- strong oxidant free radicals will also studied to understand the physical mechanism of pyro-electro-chemical coupling. We will also analyze the mechanism on basis of spontaneous polarization, surface chemical effect, energy band structure. Heterojunction structure (Ba0.7Sr0.3TiO3/TiO2) and noble metal(Ag, Pd) coating material will also be try to enhance pyrocatalytic performance. The pyroelectric electric potential distribution will also be simulated through using Comsol software. Some pyroelectric nano-materials also possess excellent photocatalytic and piezo-catalytic performances. We also plan to combine photocatalysis, piezo-catalysis with pyro-catalysis to realize high degradation ratio. The execution of this project can provide academic reference and scientific basis for the design of novel pyro-electro-chemical effect and the preparation of novel room-temperature pyro-catalyst.

光催化材料在光照下可产生电子和空穴，其在溶液中可产生强氧化的活性自由基以降解染料。在温度变化下，热释电材料可诱导出正负电荷，理论上也可诱导出活性自由基。这称为热-电-化学效应。这种新的热催化技术在室温冷热变化驱动染料降解和分解水制氢等方面应用前景广阔。本课题拟合成LiTaO3、Bi0.5Na0.5TiO3和Ba0.7Sr0.3TiO3等热释电纳米材料；给出颗粒大小和形貌、染料浓度、冷热变化速率、温度幅度、酸碱度、染料种类、催化剂添加量、少量双氧水添加等对热-电-化学耦合热催化的影响规律并优化，使降解率90%以上、研究活性自由基的产生过程、自发极化、表面化学效应、能带结构；制备异质结如Ba0.7Sr0.3TiO3/TiO2及贵金属（Ag、Pd）负载Ba0.7Sr0.3TiO3等；用Comsol软件模拟热释电势分布；研究热释电纳米材料光催化、机械催化和热催化的协同。为室温热催化的应用提供参考。

环境冷热变换如昼夜温差是自然界的普遍现象，其也是人们未来可以收集利用的一种能源。铁电材料具有自发电极化，在外加应力或冷热变化下，其电偶极子的有序排列会被破坏，表面电荷平衡被打破，从而表现出压电和热释电效应。在温度变化下，铁电材料两端可诱导出正负电荷，其进一步在溶液中与溶解氧或者氢氧根离子发生反应，可以产生具有强氧化能力的活性自由基，驱动化学氧化还原反应进行。这称为热-电-化学耦合效应。这种新的热催化技术在室温冷热变化驱动染料降解、分解水制氢清洁能源、从空气中固氮、温室气体二氧化碳还原等方面应用前景广阔。本项目中，给出了BaTiO3、BiFeO3、Bi0.5Na0.5TiO3、ZnSnO3、(K0.5Na0.5)NbO3、Ba0.75Sr0.25TiO3 (BST)等多种无铅铁电纳米催化剂材料的合成制备方法。这些热释电催化剂对染料溶液如罗丹明B、亚甲基蓝、甲基橙、酸性橙7等均表现出优异的热释电催化染料降解效果，例如对于罗丹明B溶液的降解率可达90以上。进一步地，通过负载炭黑或贵金属、直流电极化预处理、构建异质结、铁电光催化/压电催化/热释电催化协同等手段，催化染料降解性能还可以进一步提升。为室温铁电纳米材料收集环境冷热变换热能用于实现热-电-化学效应提供科学依据，也为热释电催化技术的未来实际应用提供科学参考。