Measuring Single Ion Gibbs Transfer Energies without Extrathermodynamic Assumptions to Validate the Unified Acidity and Redox Scales within the Protoelectric Potential Map PPM

PH值和氧化还原电位是常识，对分析化学、能量存储和转换(电解、燃料电池、电池)、材料科学(腐蚀、金属化)或生命科学(质子泵、质子耦合电子转移、光系统)都是非常重要的。它们的定义，例如，pH=−loga(H+)，基于单离子的热力学数量。虽然在世界范围内使用，但由于电子中和性的原因，单离子数量从根本上受到了质疑。在现有的溶液热力学理论框架中，缺少的一个主要环节是这些热力学参数在所有介质中和在所有介质之间的可比性。现在，通过使用我们小组推出的统一的酸度和氧化还原标尺phab和peabs，这是可能的。然而，目前实验测定相应氧化还原/酸碱体系的单离子吉布斯转移能是一个悬而未决的问题。到目前为止，为了达到这个目的，必须使用广泛讨论的热力学外假设，这些假设与至少1-2个pH/Pe单位(60-120 mV，在某些情况下高达1V)的不确定度有关。因此，我们的核心目标是通过测量含有不同溶剂的两个半电池之间的电势来确定严格热力学意义上的单离子吉布斯转移能。它们通过一种“理想的”盐桥连接在一起，这种盐桥充满了一种特定的离子液体，具有相同的阴离子和阳离子扩散系数。在这个装置中，在两种不同介质之间的界面上出现的液体结电势的最大部分被抵消。剩下的部分可以在没有热力学外假设的情况下确定，测得的电池电势可以直接分配给单离子转移的吉布斯能量。这将为溶液热力学提供最后一个缺失的环节，包括接受单离子数量。

pH values and redox potentials are common knowledge and of utmost importance, e.g. to analytical chemistry, energy storage and conversion (electrolysis, fuel cells, batteries), material sciences (corrosion, metallization) or life sciences (proton pump, proton coupled electron transfer, photosystem). Their definitions, e.g. pH = −log a(H+), base on thermodynamic quantities of single ions. Although used worldwide, single ion quantities are fundamentally questioned for electroneutrality reasons. A major missing link in the existing theoretical framework of solution thermodynamics was the comparability of these thermodynamic quantities in and between all media. This is now possible by using the unified acidity and redox scales pHabs and peabs introduced by our group. However, now the experimental determination of single ion Gibbs transfer energies of corresponding redox/acid-base systems is the unresolved problem. So far, heavily discussed extrathermodynamic assumptions have to be used for this purpose, which are associated with uncertainties of at least 1 – 2 pH- / pe-units (60 – 120 mV, in some cases up to 1 V).Our core objective, therefore, is the determination of single ion Gibbs transfer energies in a strict thermodynamic sense by means of potential measurements between two half cells containing different solvents. They are connected – and this is new and crucial – by an “ideal” salt bridge, filled with a specific ionic liquid with identical diffusion coefficients of anion and cation. In this set up, the largest parts of the liquid junction potential occurring at interfaces between two different media cancel. The remaining parts can then be determined without extrathermodynamic assumptions and the measured cell potential can be directly assigned to the Gibbs energy of transfer of single ions. This would provide the last missing link for solution thermodynamics, including acceptance of single ion quantities.