An unprecedented polyoxoniobate (PONb) oligomer was obtained by addition of a methylene blue (MB) dye solution over the PONb solution formed a blue nanogel that was converted into a stable blue solid through a lyophilization process. The new solid composite, so-called “blue polyoxoniobate” (blue-PONb), presents a two-dimensional (2D) morphology with electrochemical performance that stand out among the materials used in redox supercapacitor technology. This new material was evaluated as supercapacitor electrode showing a high areal specific capacitance and power density that reaches 110.50 mF cm and 8.49 mW cm. In addition, in this composite the redox additive (MB) and the PONb presented a peculiar electrochemical behavior, the reduction of the niobium species and the transfer of electrons necessary for the accumulation of charge occurring simultaneously. As a result, blue-PONb electrode maintains the cycling performance with high coulombic efficiency (∼99 %) over the 50,000 cycles evaluated. Here, the origins of the electrochemical stability and the mechanism of operation of the blue-PONb electrode are analyzed and discussed. Finally, this work presents a PONb as a new and promising class of redox-capacitive materials with matrix/redox shuttle synergism.

中文翻译：

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基于铌低聚物的前所未有的混合多金属氧酸盐：作为氧化还原超级电容器电极的显着应用


通过在 PONb 溶液上添加亚甲基蓝 (MB) 染料溶液，形成蓝色纳米凝胶，通过冻干过程将其转化为稳定的蓝色固体，从而获得了前所未有的聚氧铌酸盐 (PONb) 低聚物。这种新型固体复合材料被称为“蓝色聚氧铌酸盐”（blue-PONb），呈现出二维（2D）形态，其电化学性能在氧化还原超级电容器技术中使用的材料中脱颖而出。这种新材料被评估为超级电容器电极，表现出高面积比电容和功率密度，分别达到110.50 mF cm和8.49 mW cm。此外，在该复合材料中，氧化还原添加剂（MB）和PONb呈现出独特的电化学行为，铌物质的还原和电荷积累所需的电子转移同时发生。因此，蓝色 PONb 电极在评估的 50,000 次循环中保持了高库伦效率 (∼99%) 的循环性能。在这里，分析和讨论了蓝色 PONb 电极的电化学稳定性的起源和工作机制。最后，这项工作提出了 PONb 作为一类具有基质/氧化还原穿梭协同作用的新型且有前途的氧化还原电容材料。