Carbonized Eggshell Membranes as a Natural and Abundant Counter Electrode for Efficient Dye‐Sensitized Solar Cells
Carbonized Eggshell Membranes as a Natural and Abundant Counter Electrode for Efficient Dye‐Sensitized Solar Cells
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DOI：
10.1002/aenm.201401524
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发表时间：
2015-03
影响因子：
27.8
通讯作者：
Chih-Liang Wang;Jinyun Liao;Sheng‐Heng Chung;A. Manthiram
中科院分区：
文献类型：
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作者：
Chih-Liang Wang;Jinyun Liao;Sheng‐Heng Chung;A. Manthiram
DOI：10.1002/aenm.201401524被认为是典型Pt电极的潜在替代品。例如，Grätzel的小组和Gao的小组分别探索了海带的大孔结构（超过50 nm）和橡树的中孔结构（2-50 nm）。[5，6]然而，电化学活性和微观结构之间的关系仍然不清楚，并且由微孔（小于2nm）组成的天然衍生CE尚未作为CE应用于DSSC。在这篇文章中，我们提出了一种天然来源的碳质材料作为DSSC的无Pt CE。这种材料是由从生活垃圾中回收的蛋壳膜制成的。结果表明，蛋壳膜具有丰富的微孔结构，能有效地促进电荷转移过程，从而提高了DSSC的开路电压V_c，并具有与传统Pt基CE相比的竞争效率。图1a显示了碳化前蛋壳膜的扫描电子显微镜（SEM）图像。它表现出交织聚结纤维的缠结结构，形成高度多孔的微观结构。为了进一步提高电导率，将蛋壳膜表面涂覆一层碳。通过将新鲜蛋壳膜浸入蔗糖溶液中，然后在800 °C下碳化来制备经蔗糖涂覆的蛋壳膜（CSEMs）。CSEM的均匀粗化和增厚的形态，可再生太阳能的最终目标是开发低成本、高效率的光伏技术，以满足未来太瓦级太阳能的需求。染料敏化太阳能电池（DSSC）的光电转换效率超过12%，具有组装简单、成本低廉、环境友好等优点，被认为是下一代太阳能电池最有前途的候选材料之一。[ 1 ] DSSC的原型结构由n型TiO 2的多孔膜、光敏染料、由I /I3 − − I电解质组成的氧化还原对和Pt对电极（CE）组成。铂的贵金属性和稀缺性以及其在电解质中的稳定性差已经成为实现DSSC的低成本和大规模部署的重要障碍。在太阳光照射下，染料分子经历从基态到激发态的电子跃迁。这是其次是一个超快的电子注入从激发态的染料分子到二氧化钛的导带，这导致染料分子的氧化。氧化后的染料在电解液中刺激碘离子氧化成三碘离子，注入TiO 2导带的电子被传输到CE。CE的功能是从三碘化物中再生碘化物，以完成光电转换过程。因此，CE的电性能和催化能力在DSSC过程中起着重要作用。之前探索作为CE铂替代品的材料包括碳质材料、导电聚合物、金属化合物和复合材料。[ 2 ]然而，涉及有毒和/或复杂合成过程或含有脆弱微结构的材料对于大规模制造来说变得具有挑战性。与这些材料相反，直接从我们周围环境中提取的天然材料是丰富的，可获得的，并且是环保的。几种由独特结构组成的天然衍生材料已被开发用于高级应用，如合成模板，光子晶体，超级电容器，Li-S电池和DSSC。[第3、4页]
DOI: 10.1002/aenm.201401524 recognized as a potential substitute for the typical Pt electrode. For instance, the macroporous structure (beyond 50 nm) of carbonized sea tangle and the mesoporous structure (2–50 nm) of carbonized oak have been explored by, respectively, Grätzel’s group and Gao’s group. [ 5,6 ] However, the relationships between the electrochemical activity and the microstructure remain unclear and naturally derived CEs composed of micropores (less than 2 nm) have not yet been applied to DSSCs as CEs. In this communication, we present a naturally derived carbonaceous material as a Pt-free CE for DSSCs. The material was made from eggshell membranes that were recycled from domestic waste. It is found that the unique micropore-rich, hierarchically porous microstructure of eggshell membranes can effectively facilitate the charge-transfer process, leading to an improved open-circuit voltage V oc and a competitive effi ciency as compared with a DSSC with a traditional Pt-based CE. Figure 1 a shows the scanning electron microscopy (SEM) image of an eggshell membrane before carbonization. It exhibits an entangled architecture of interwoven coalescing fi bers, which form a highly porous microstructure. To further enhance the electrical conductivity, the carbonized eggshell membranes were surface coated with a layer of carbon. The carbonized sucrose-coated eggshell membranes (CSEMs) were prepared by immersing the fresh eggshell membranes into a sucrose solution and then carbonizing at 800 °C. The uniformly coarsened and thickened morphology of the CSEM in The ultimate goal of renewable solar energy is aimed at developing low-cost, high-effi ciency photovoltaic technologies that can satisfy the demand for future terawatt-scale solar energy. The dye-sensitized solar cells (DSSC), with a light–electricity conversion effi ciency exceeding 12%, are considered to be one of the most promising candidates for next-generation solar cells due to their facile assembly, cost-effectiveness, and environmental friendliness. [ 1 ] The prototypical architecture of a DSSC consists of a porous fi lm of n-type TiO 2 , a photosensitized dye, a redox couple consisting of I /I3 − − Ielectrolyte, and a Pt counter electrode (CE). The noble and scarce nature of Pt as well as its poor stability in the electrolyte has become a signifi cant hurdle to realize low-cost, and thus, large-scale, deployment of DSSCs. Upon solar illumination, the dye molecule undergoes an electronic transition from the ground state to the excited state. This is followed by an ultrafast electron injection from the excited state of the dye molecule into the conduction band of TiO 2 , which leads to the oxidation of the dye molecule. The oxidized dye subsequently stimulates the oxidation of iodide into triiodide in the electrolyte, and the electron injected into the conduction band of TiO 2 is transported to the CE. The function of the CE is to regenerate iodide from triiodide in order to complete the light–electricity conversion process. Accordingly, the electrical properties and catalytic ability of the CE play a signifi cant role in the DSSC process. Materials previously explored as alternatives to Pt for CEs include carbonaceous materials, conductive polymers, metal compounds, and composite materials. [ 2 ] However, materials that involve toxic and/or complex synthesis processes or that contain vulnerable microstructures, become challenging for large-scale manufacturing. In contrast to such materials, natural materials drawn directly from our surroundings are abundant, accessible, and environmentally friendly. Several naturally derived materials, composed of unique structures, have been developed for advanced applications, such as synthesis templates, photonic crystals, supercapacitors, and Li–S batteries, and DSSCs. [ 3,4 ]