新型高效复合对电极材料的设计、合成及其催化性能研究

Dye-sensitized solar cell is a new-generation green and efficient photovoltaic device, but the commonly used platinum counter electrode is expensive and easy to corrosion, and the new Pt-free candidates cannot meet the multiple requirements for high catalytic activity, high conductivity and high stability, which have seriously restricted the practical application of solar cell. The project will develop a self-assembly controllable synthesis technique and creatively construct a new kind of low-cost, high-efficiency and stable metal-nitrogen-ordered mesoporous carbon composite electrode, with the covalent-bonding heterointerface between the metal-nitrogen component, nitrogen heteroatom and carbon matrix. This work will flexibly regulate the type and distribution of metal-nitrogen, the concentration and state of nitrogen, and rationally design the mesopore size of the conductive carbon matrix, aiming at improving the activity and density of catalytic sites, accelerating the electron transport and migration, enhancing the ion diffusion and adsorption, and finally achieving an excellent catalytic activity for the electrode material. In addition, these studies will adopt a heterogeneous chemical bonding strategy to establish an integrated metal-nitrogen-carbon heterointerface structure, for the purpose of further reducing the interfacial contact impedance and stabilizing the catalytic active component. Finally, the research will deeply investigate the electrocatalytic activity, interfacial adsorption and diffusion kinetics of the electrode materials, revealing the intrinsic link of the composition-structure-catalytic activity and developing the electrocatalytic mechanism. The controllable synthesis mechanism, heterointerface bonding design and structure-activity relationship research in this project will pave a new way for the oriented synthesis of high-performance counter electrode material and easy fabrication of highly efficient dye-sensitized solar cell.

染料敏化太阳能电池是新一代绿色高效的光伏器件，但使用的铂对电极昂贵且易腐蚀，而替代铂的新型对电极又难以满足兼具高催化活性、高导电性与高稳定性的要求，严重制约了电池的实际应用。本项目拟利用水热自组装可控合成新技术，开发一类低价、高效且稳定的由金属-氮组分、氮杂原子与碳基体进行界面共价键合构筑的金属-氮-有序介孔碳复合型对电极。通过调控金属-氮类型与分布、氮量与氮态、以及合理设计导电碳基体的介孔孔径，提高催化位点活性与密度，加快电子传输与迁移，增大离子扩散与吸附，制备出催化性能优异的电极材料；通过异质化学键合策略构建一体化金属-氮-碳界面结构，进一步降低界面阻抗，稳固活性组分；并深入研究材料的电催化活性、界面吸附与扩散动力学，揭示出电极材料组分、界面及结构与性能的内在联系及电催化机制。本项目的可控合成机制、异质键合界面设计及构效关系研究将为高性能电极材料导向合成及高效太阳能电池制备提供新途径。

染料敏化太阳能电池是新一代绿色高效的光伏器件，但使用的铂对电极昂贵且易腐蚀，而替代铂的新型对电极又难以满足兼具高催化活性、高导电性与高稳定性的要求，严重制约了电池的实际应用。本项目采用有机-有机超分子自组装策略，通过低温水热共聚反应制备高分子有机碳源与表面活性剂胶束有序共组装前驱体，经高温碳化-氮化共聚物与有机氮源、碳热还原金属有机膦酸盐、无机金属磷酸盐制备了系列兼具高催化活性组分，共价键合界面与有序介孔孔道的新型碳基复合对电极催化材料（NOMC-Ni@NCNTs，CoP-NMC, Mo2C/NCNTs@Co，MxP-NCNTs，Sn-P@PCMs）。设计开发的染料敏化太阳能电池用系列新型碳基复合对电极催化材料具有高活性位点密度，快速电子传输与迁移，高速离子扩散与吸附等优异特性，表现出大的极限交换电流密度（9.5 mA cm-2）与扩散电流密度（73.7 mA cm-2），高的电催化活性（1.4 Ω）与光电转换效率（8.53%），优于铂基电池的相应性能（7.52%）。通过XPS，紫外可见吸收光谱及DFT理论计算揭示了新型碳基复合材料的电催化机制。研究发现活性金属磷化物晶体结构中带正电性的金属活性中心（Mδ+）能化学吸附碘三根离子形成金属-碘共价键从而降低了催化碘-碘键断裂所需活化能（0.5 eV），加速了碘三根离子催化还原速率。此外，我们发现设计制备的异质界面能级匹配的新型复合电催化剂Mo2C/ NCNTs@Co有效提高了对电极电催化活性。通过UPS能谱数据分析与DFT理论计算得出了其催化作用促进机制：金属与氮共掺杂碳纳米管有效降低了碳原子电子功函（4.85→4.63 eV）有利于电子从碳管表面迁移至负载活性组分碳化钼，同时碳化钼与碘三根离子电解液能级相匹配具有较高的吸附碘三根离子、脱附碘负离子可逆性与较高的碘三根离子催化还原活性（1.3 Ω）。最后，我们构建了异质键合界面结构的MxP-NCNTs电催化剂，解决了各组份间电子接触不良，活性组分易流失的问题，获得了较好的电催化活性，电化学稳定性与光电转换效率。本项目的可控合成机制、异质键合界面设计及构效关系研究为高性能电极材料导向合成及高效太阳能电池制备提供了新途径。