Catalytic Duality of Platinum Surface Oxides in the Oxygen Reduction and Hydrogen Oxidation Reactions

Hydrogen Oxidation Artifact During Platinum Oxide Reduction in Cyclic Voltammetry Analysis of Low-Loaded PEMFC Electrodes

“…In this study, we investigate an artifact peak overlapping the PtOx reduction peak measured in the cathodic transient of cyclic voltammetry analysis of ultra-low-loaded catalyst layers through a parametric analysis. Considering findings by Tahmasebi et al [29] and Zhao et al [30] with respect to comparable oxidation peaks, we conclude that this peak is caused by spontaneous HOR of previously accumulated crossover hydrogen (H 2X ). Two requirements must be fulfilled for this feature to be measured.…”

“…At lower scan rates, the currents in the potential window decrease due to the decrease in H 2X bias as a result of PtOx formation, which will be explained in more detail in the following section. During the cathodic CV transient, PtOx reduction proceeds at potentials of about 0.7 to 1.1 V. Typically, the reduction would continue to even lower potentials of about 0.6 [29], but the artifact appears as a positive oxidation peak overlapping the reduction current. With higher scan rates, the artifact starts at lower potentials (E Red ), inset of Fig.…”

“…double-layer charging or H-adsorption. For example, if all Pt sites are occupied by atomic hydrogen, the doubling in scan rate will result in twice the current magnitude in the potential range of 0.1-0.3 V, while integration would result in an almost constant charge transfer as H-adsorption and double-layer charging are relatively fast processes [29]. Vice versa, a disproportional change in current and significant differences in transferred charges would hint towards a Faradaic process, which is controlled or dominated by the diffusion of reactants and/or products.…”

“…In literature, few comparable oxidation peaks during the reverse (cathodic) scan of CVs have been reported. Tahmasebi et al [29] investigated electrocatalytic reactions occurring on a Pt wire acting in an all-glass electrochemical cell under atmospheres saturated with N 2 , oxygen (O 2 ), or H 2 and found this oxidation peak during the cathodic scan, once the setup and electrode was saturated with H 2 . They associated this peak to an "increased catalytic activity" towards H 2 oxidation reaction (HOR), which indicates the necessity of H 2 to be present for the artifact to occur.…”

Influência Da Composição Dos Nanofios Pt-Ir/C Na Atividade Catalítica Frente a Oxidação Eletroquímica De Etanol Em Meio Ácido

“…O perfil obtido se assemelha ao perfil da platina policristalina. 27 Foram observados picos redox típicos, associados à adsorção/ dessorção de H 2 que é formado pela oxidação do hidrogênio absorvido (varredura anódica) e redução de íons de H + presentes na solução (varredura catódica) entre 0,05-0,3 V vs. EHMS. O eletrodo entre 0,3 e 0,7 V se comporta como idealmente polarizado apresentando apenas correntes capacitivas correspondentes à acomodação dos íons na dupla camada.…”