各校計畫成果

活動簡介

電荷傳輸是一種支撐許多現代技術的基本過程，我們的研究聚焦於揭示如何在分子固體中促進這一過程，特別是體相與界面上的離子與電子傳輸，藉此推動各種應用，例如作為能量儲存／轉換裝置中的離子／電荷導體，以及作為非勻相催化材料。最終，我們的目標是提供理性設計固體所需的見解，從而加速應對社會相關挑戰的化學技術發展。

在我們研究結構－性質－功能關係的過程中，其中一個面向是評估並開發分析固體結構與性質的方法，特別針對那些由於結構不均勻而難以用常規分析方法表徵的材料。以我們在本報告期間發表的成果為例，我們評估了一種分析方法（X 射線光電子能譜，XPS），用於一類稱為石墨相氮化碳（graphitic carbon nitride，gC₃N₄）的化合物進行結構鑑定。這些化合物被視為有潛力應用於太陽能燃料生成的有機半導體，然而由於其結構無序的特性，其分子結構難以確定。此外，普遍認為 gC₃N₄ 中的晶體缺陷賦予母體材料有用的性質，包括快速界面電荷轉移的能力，但由於缺陷濃度低，其結構鑑定一直相當困難。

我們的發表評估了 XPS 對 gC₃N₄ 及其缺陷的結構鑑定之適用性，並檢視了此光譜技術的定量準確度。在此，我們採用分子模型的方法，即以結構明確的小分子來模擬複雜化學體系（此處為 gC₃N₄）的結構。對這些分子模型的 XPS 分析顯示，此技術不僅缺乏足夠的光譜解析度來區分 gC₃N₄ 上不同官能基，還存在高達 70% 的定量不確定性。儘管 XPS 廣泛應用於固態分析，我們的結果揭示了該技術的侷限性，並激勵我們開發可用於此類及其他功能材料的定量結構分析方法。

Charge transport is a process underpinning many modern technologies, and our research focuses on uncovering how this process, specifically ionic and electronic transport in the bulk and at the interface, can be promoted within molecular solids, which could enable various applications such as ionic/charge conductors in energy storage/conversion devices and as heterogeneous catalysis. Ultimately, we aim to furnish the insights necessary for the rational design of solids, thereby accelerating the development of chemical technologies that tackle challenges of societal relevance.
As part of our research in delineating structure-property-function relationship, one aspect in our work is evaluating and developing methods of analyzing the structure and properties of solids, particularly those that are difficult to characterize using routine analytic methods owing to structural inhomogeneity. Using our publication during this reporting period as an example of our achievements, we evaluated one analytical method (x-ray photoelectron spectroscopy or XPS) for the structural characterization of a class of compounds known as graphitic carbon nitride or gC₃N₄. These compounds are considered to be organic semiconductors with potential applications in solar fuel production, although their molecular structure is difficult to determine due to their amorphous nature. Moreover, it is widely accepted that crystallographic defects within gC₃N₄ impart useful properties to the parent material, including the ability for fast interfacial charge transfer, though structural characterization of such defects has proven difficult due to their low concentration. Our publication assessed the suitability of XPS for the structural characterization of gC₃N₄ and their defects, and assessed the quantitative accuracy of this spectroscopic method. Here, we employ the methodology of molecular models, whereby a complex chemical system (gC₃N₄ in this case) is structurally emulated by small molecules with unambiguous structure. XPS analyses of these molecular models show that this technique not only lacks the spectral resolution to discriminate different functional groups on gC₃N₄, but also has large quantification uncertainty of up to 70%. Despite the fact that XPS is widely used for solid state analysis, our results demonstrate the limitation of this technique and motivate us to develop methods for quantitative structural analysis for this and other classes of functional materials.