Polyoxometalates (POMs) have been considered as an efficient catalyst for triiodide reduction in dye-sensitized solar cells (DSSCs). However, agglomeration of POMs limits the improvement in power conversion efficiency (PCE) of DSSCs. In this paper, we improve our previous synthesis process by a simple ultrasonic driving strategy. A series of highly dispersed POM nanoparticles periodically deposited on multi-walled carbon nanotube (MWCNT) nanocomposites (abbreviated as POMs/CNTs) is synthesized, which increases the active sites by improving the dispersion degree and inhibiting the aggregation of POM molecules. Additionally, CNTs as a conductive support skeleton and physical barrier promote the rapid electron transfer and protect POM molecules from chemical degradation. The nanocomposites exhibit well-distributed morphology, and highly dispersed POM nanoparticles about tens of nanometers in diameter are in intimate contact with CNTs. Powder X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy demonstrate that POM nanoparticles have been periodically deposited on CNTs. POM/CNT counterelectrodes (CEs) exhibit a more remarkable performance towards triiodide reduction than pure CNT CEs, indicating that POMs deposited on CNTs boost electrocatalytic triiodide reduction. Among these POM/CNT CEs, the Co₄PW₉/CNT CE exhibits the best photovoltaic behavior with a high power conversion efficiency (PCE) of 7.60%, which is superior to that of the Pt CE (6.59%). The excellent activity originates from the synergistic effect between the high redox activity of POMs and the excellent conductive ability of CNTs. This work provides a foundation for preparing advanced high-efficient CE catalysts of POM materials.

中文翻译：

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高度分散的氧化还原活性多金属氧酸盐在多壁碳纳米管上的周期性沉积，以促进染料敏化太阳能电池中三碘化物的电催化还原

多金属氧酸盐（POM）被认为是染料敏化太阳能电池（DSSC）中三碘化物还原的有效催化剂。但是，POM的聚集限制了DSSC的功率转换效率（PCE）的提高。在本文中，我们通过简单的超声波驱动策略改进了先前的合成过程。合成了周期性沉积在多壁碳纳米管（MWCNT）纳米复合材料（缩写为POMs / CNT）上的一系列高度分散的POM纳米颗粒，通过改善分散度和抑制POM分子的聚集来增加活性位点。另外，作为导电支撑骨架和物理屏障的CNT促进了电子的快速转移并保护了POM分子免于化学降解。纳米复合材料表现出分布均匀的形态，直径约数十纳米的高度分散的POM纳米粒子与CNT紧密接触。粉末X射线衍射，X射线光电子能谱，扫描电子显微镜和透射电子显微镜证明，POM纳米颗粒已定期沉积在CNT上。POM / CNT对电极（CEs）在还原三碘化物方面表现出比纯CNT CEs更出色的性能，这表明沉积在CNT上的POM促进了电催化三碘化物的还原。在这些POM / CNT CE中，POM / CNT对电极（CEs）在还原三碘化物方面表现出比纯CNT CEs更出色的性能，这表明沉积在CNT上的POM促进了电催化三碘化物的还原。在这些POM / CNT CE中，POM / CNT对电极（CEs）在还原三碘化物方面表现出比纯CNT CEs更出色的性能，这表明沉积在CNT上的POM促进了电催化三碘化物的还原。在这些POM / CNT CE中，₄ PW ₉ / CNT CE表现出最佳的光伏性能，具有7.60％的高功率转换效率（PCE），优于Pt CE（6.59％）。优异的活性源于POM的高氧化还原活性和CNT优异的导电能力之间的协同作用。该工作为制备POM材料的先进高效CE催化剂提供了基础。