Three-dimensional nitrogen-doped graphene/reduced hydroxylated carbon nanotube composite aerogel (NG/CNT-OH) with unique hierarchical porosity and mechanical stability is developed through a two-step hydrothermal reaction. With plenty of exposed active sites and efficient multidimensional transport pathways of electrons and ions, NG/CNT-OH exhibits great electrocatalytic performances for I⁻/I₃ ⁻ redox couple. The subsequent compressed NG/CNT-OH papers possess high electrical conductivity and good flexibility, thus generating high-performance flexible counter electrodes (CEs) with transparent conducting oxide free (TCO-free) for dye-sensitized solar cells (DSSCs). The flexible NG/CNT-OH electrodes show good stability and the DSSCs with the optimized NG/CNT-OH CE had higher short-circuit current density (13.62 mA cm⁻²) and cell efficiency (6.36%) than DSSCs using Pt CE, whereas those of the DSSCs using Pt CE were only 12.81 mA cm⁻² and 5.74%, respectively. Increasing the ratio of hydroxylated carbon nanotubes (CNT-OH) to the graphene oxide (GO) in the reactant would lead to less content of doped N, but better diffusion of electrolyte in the CEs because of more complete GO etching reaction. The design strategy presents a facile and cost effective way to synthesis three-dimensional graphene/CNT composite aerogel with excellent performance, and it can be potentially used as flexible TCO-free CE in other power conversion or energy storage devices.

中文翻译：

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透明无导电氮掺杂石墨烯/还原羟基化碳纳米管复合纸作为染料敏化太阳能电池的柔性对电极

通过两步水热反应，开发了具有独特的分级孔隙率和机械稳定性的三维氮掺杂石墨烯/还原羟基化碳纳米管复合气凝胶（NG / CNT-OH）。随着大量的电子和离子的暴露的活性位点和效率的多维运输途径的，NG / CNT-OH为我显示出很大的电催化性能^- / I ₃ ^-氧化还原夫妇。随后的压缩NG / CNT-OH纸具有较高的电导率和良好的柔韧性，从而产生了用于染料敏化太阳能电池（DSSC）的具有透明无导电氧化物（TCO-free）的高性能柔性对电极（CE）。柔性NG / CNT-OH电极显示出良好的稳定性，并且采用优化的NG / CNT-OH CE的DSSC与使用Pt CE的DSSC相比，具有更高的短路电流密度（13.62 mA cm ^-2）和电池效率（6.36％），而使用Pt CE的DSSC仅为12.81 mA cm ^-2和5.74％。增加反应物中羟基化碳纳米管（CNT-OH）与氧化石墨烯（GO）的比例将导致掺杂N的含量降低，但由于GO蚀刻反应更加完全，CE中电解质的扩散更好。该设计策略为合成具有优异性能的三维石墨烯/ CNT复合气凝胶提供了一种简便且经济高效的方法，它有可能在其他功率转换或储能设备中用作无TCO的柔性CE。