Department of Materials Science and Engineering, University of Washington , Seattle, Washington 98195, United States.
Department of Electrical Engineering, University of California , Santa Cruz, California 95064, United States.
ACS Appl Mater Interfaces. 2018 Jan 17;10(2):1933-1938. doi: 10.1021/acsami.7b16640. Epub 2018 Jan 4.
Charge transfer at the interface between the active layer and the contact is essential in any device. Transfer of electronic charges across the contact/active layer interface with metal contacts is well-understood. To this end, noble metals, such as gold or platinum, are widely used. With these contacts, ionic currents (especially protonic) are often neglected because ions and protons do not transfer across the interface between the contact and the active layer. Palladium hydride contacts have emerged as good contacts to measure proton currents because of a reversible redox reaction at the interface and subsequent absorption/desorption of H into palladium, translating the proton flow reaching the interface into an electron flow at the outer circuit. Here, we demonstrate that gold and palladium contacts also collect proton currents, especially under high relative humidity conditions because of electrochemical reactions at the interface. A marked kinetic isotope effect, which is a signature of proton currents, is observed with gold and palladium contacts, indicating both bulk and contact processes involving proton transfer. These phenomena are attributed to electrochemical processes involving water splitting at the interface. In addition to promoting charge transfer at the interface, these interfacial electrochemical processes inject charge carriers into the active layer and hence can also modulate the bulk resistivity of the materials, as was found for the studied peptide fibril films. We conclude that proton currents may not be neglected a priori when performing electronic measurements on biological and bioinspired materials with gold and palladium contacts under high humidity conditions.
在任何设备中，活性层与接触之间的电荷转移都是至关重要的。金属接触在接触/活性层界面处的电子电荷转移已经得到了很好的理解。为此，广泛使用贵金属，如金或铂。对于这些接触，通常忽略离子电流（特别是质子电流），因为离子和质子不会在接触和活性层之间的界面处转移。由于界面处的可逆氧化还原反应以及随后钯中 H 的吸收/解吸，将到达界面的质子流转化为外电路中的电子流，因此钯氢化物接触已成为测量质子电流的良好接触。在这里，我们证明金和钯接触也会收集质子电流，特别是在高相对湿度条件下，因为界面处的电化学反应。在金和钯接触时观察到明显的动力学同位素效应，这是质子电流的特征，表明涉及质子转移的体相和接触过程。这些现象归因于界面处涉及水分解的电化学过程。除了促进界面处的电荷转移外，这些界面电化学过程还会向活性层注入载流子，因此也可以调节材料的体电阻率，如研究的肽原纤维膜所示。我们得出结论，在高湿度条件下使用金和钯接触对生物和仿生材料进行电子测量时，不能先验地忽略质子电流。
