Artmann Evelyn, Menezes Pramod V, Forschner Lukas, Elnagar Mohamed M, Kibler Ludwig A, Jacob Timo, Engstfeld Albert K
Institute of Electrochemistry, Ulm University, D-, 89081, Ulm, Germany.
Chemphyschem. 2021 Dec 3;22(23):2429-2441. doi: 10.1002/cphc.202100433. Epub 2021 Nov 2.
Applying a voltage to metal electrodes in contact with aqueous electrolytes results in the electrolysis of water at voltages above the decomposition voltage and plasma formation in the electrolyte at much higher voltages referred to as contact glow discharge electrolysis (CGDE). While several studies explore parameters that lead to changes in the I-U characteristics in this voltage range, little is known about the evolution of the structural properties of the electrodes. Here we study this aspect on materials essential to electrocatalysis, namely Pt, Au, and Cu. The stationary I-U characteristics are almost identical for all electrodes. Detailed structural characterization by optical microscopy, scanning electron microscopy, and electrochemical approaches reveal that Pt is stable during electrolysis and CGDE, while Au and Cu exhibit a voltage-dependent oxide formation. More importantly, oxides are reduced when the Au and Cu electrodes are kept in the electrolysis solution after electrolysis. We suspect that H O (formed during electrolysis) is responsible for the oxide reduction. The reduced oxides (which are also accessible via electrochemical reduction) form a porous film, representing a possible new class of materials in energy storage and conversion studies.
向与水性电解质接触的金属电极施加电压，会在高于分解电压时导致水电解，并在更高电压下在电解质中形成等离子体，这被称为接触辉光放电电解（CGDE）。虽然有几项研究探讨了导致该电压范围内电流 - 电压（I - U）特性变化的参数，但对于电极结构性质的演变却知之甚少。在此，我们针对电催化的关键材料，即铂（Pt）、金（Au）和铜（Cu）来研究这一方面。所有电极的静态I - U特性几乎相同。通过光学显微镜、扫描电子显微镜和电化学方法进行的详细结构表征表明，铂在电解和CGDE过程中是稳定的，而金和铜则表现出电压依赖性的氧化物形成。更重要的是，在电解后将金和铜电极保持在电解液中时，氧化物会被还原。我们怀疑电解过程中形成的H₂O是氧化物还原的原因。还原后的氧化物（也可通过电化学还原获得）形成多孔膜，这代表了储能和能量转换研究中一类可能的新型材料。
