Mild aqueous electrolytes containing multivalent metal salts are currently scrutinized for the development of ecosustainable energy-related devices. However, the role of soluble multivalent metal ions in the electrochemical reactivity of transition metal oxides is a matter of debate, especially when they are performed in protic aqueous electrolytes. Here, we have compared, by means of (spectro)electrochemistry, the reversible electrochromic reduction of transparent nanostructured γ-WO₃ thin films in mild aqueous electrolytes of various chemical composition and pH. This study reveals that reversible proton insertion is the only charge storage mechanism over a large pH range and that it is effective for aqueous electrolytes prepared from either organic (such as acetic acid) or inorganic (such as solvated multivalent cations) Bro̷nsted acids. By refuting charge storage mechanisms relying on the reversible insertion of multivalent metal ions, notably in aqueous electrolytes based on Al³⁺ ions or a mixture of Al³⁺ and Zn²⁺ ions, these fundamental results pave the way for the rational development of electrolytes and active materials for a range of aqueous-based devices, such as the emerging concept of an energy-saving smart window, which we also address in this study.

中文翻译：

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多价离子与质子从温和水电解质插入纳米结构电致变色 WO3

目前，人们正在仔细审查含有多价金属盐的温和水性电解质，以开发生态可持续能源相关设备。然而，可溶性多价金属离子在过渡金属氧化物电化学反应中的作用仍存在争议，特别是当它们在质子水性电解质中进行时。在这里，我们通过（光谱）电化学的方式比较了透明纳米结构γ-WO ₃薄膜在不同化学成分和pH值的温和水性电解质中的可逆电致变色还原。这项研究表明，可逆质子插入是大 pH 范围内唯一的电荷存储机制，并且它对于由有机（例如乙酸）或无机（例如溶剂化的多价阳离子）布朗斯台德酸制备的水性电解质有效。通过反驳依赖于多价金属离子可逆插入的电荷存储机制，特别是在基于 Al ^{3+离子或 Al 3+}和 Zn ²⁺离子混合物的水性电解质中，这些基本结果为电解质的合理开发铺平了道路以及用于一系列水基设备的活性材料，例如节能智能窗户的新兴概念，我们也在本研究中讨论了这一点。