氧化物的氧空位调控及其在催化电极-氧化还原电解质电容体系中的性能研究

Oxygen vacancies represent a type of intrinsic point defects in metal oxides, which can effectively enhance the conductivities, redox activities, adsorptive and catalytic abilities of oxides. Therefore, oxygen vacancies pave a significant avenue to construct high-performance capacitive system. In this project, oxygen vacancies containing faradic oxides are intended to be deposited onto current collector, so as to yield enhanced specific capacitances, rate capabilities and cycleabilities of electrodes through the tuning of oxygen vacancies concentration. Additionally, redox mediators are introduced into the electrolyte to build oxygen vacancies enriched oxides catalytic electrodes-redox species mediated electrolyte systems, so that enable the sufficient and rapid redox reactions of mediators by the catalysis of oxygen vacancies. The specific capacitances and rate capabilities of the capacitive system would therefore be improved by the cumulative faradic capacitance contributions and rapid redox kinetics of electrode and electrolyte. Based on the experimental results, fundimental influence mechanisms of surface oxygen vacancies features on the capacitive performances of catalytic electrode-redox electrolyte system would be elucidated. Furthermore, asymmetric supercapacitors containing double electrolytes are assembled according to the different potential ranges of catalytic electrode-redox electrolyte systems, therefore substantially enhance the energy densities of devices through the maximized device specific capacitances and the widened voltage windows. The ultimate goal of this project is to provide essential designing idea and experimental foundation for the construction of efficient capacitive systems based on catalytic electrode-redox electrolyte and the enhancement in energy densities of supercapacitors.

氧空位是金属氧化物的一种本征点缺陷，能有效提高氧化物的导电性、氧化还原活性、吸附以及催化活性，是构建高性能电容体系的重要途径。本项目拟在集流体表面沉积具有表面氧空位的法拉第氧化物，通过调控氧空位浓度提高氧化物电极的比容、倍率和循环性能。进而在电解质中引入氧化还原活性物质，利用氧空位的催化作用构建氧空位氧化物催化电极-氧化还原电解质体系，促进电解质的充分、快速法拉第反应。通过电极自身和电解质的双重法拉第电容贡献以及较快反应速率，提高电极体系的比容和倍率性能，揭示法拉第氧化物的表面氧空位特性对体系电容性能的影响规律。根据不同催化电极-氧化还原电解质体系的电位区间差异，组装双电解质非对称电容器件，通过提高器件比容和拓宽电压窗口，大幅提升器件能量密度；为高性能催化电极-氧化还原电解质电容体系的构建及电容器件能量密度的提升提供重要设计思路及实验依据。

在项目支持下，我们设计合成了一系列法拉第材料，通过双金属协同、质异结界面电荷分配等策略提高其法拉第活性；并通过构筑低维阵列、多级结构以及与石墨烯复合，优化电子离子扩散速率，研究法拉第电极材料组成、形貌、界面相互作用等物理化学特性与其储能性能之间的构效关系。进而匹配碳质电容电极组装非对称电容器件，获得了均衡的能量、功率密度，良好循环性能和较慢自放电速率。考虑到电解质中氧化还原活性物质能充分参与电极表面法拉第反应，我们以惰性泡沫镍作电极，在碱性电解质中引入氧化还原活性物质，通过[Fe(CN)6]3-/4-电对的充分、快速法拉第反应，以及电极与电解质的相互促进作用，大幅提高电极体系及电容器件输出性能。此外，根据过渡金属化合物对水相电解质电解的催化作用，拓展了OER、HER双功能催化剂的设计和性能优化工作。项目基本达到了预期的成果目标，为课题组在电容和电催化领域的后续研究打下了坚实的基础。