Structural effects on voltammograms of the high index planes of Pd in alkaline solution

Electrochemical Behavior and Shape Evolution of Structured Pd Nanoparticles in Alkaline Media─Influence of Electrochemically Absorbed Hydrogen

“…In the acidic medium, the CV profiles reveal the following: (i) a flat, featureless double-layer charging region of very low current ( I ) for both Pd NCs and Pd NOs (0.35–0.70 V); (ii) two well-defined cathodic and anodic peaks attributed to the UPD H; the shape of these features depends on the shape of the Pd NPs; and (iii) the current of the peaks at lower potentials is much lower than that of the peaks at higher potentials (Figure a,b). These CV characteristics are in good agreement with our previously reported results and indicate that the NPs and the experimental setup are very clean. , In the alkaline medium, the behavior is significantly different and the CV profiles reveal the following: (i) a narrow double-layer charging region with a significant current (0.55–0.70 V for the Pd NCs and 0.45–0.70 V for the Pd NOs); (ii) in the case of the Pd NCs, two anodic peaks (at E = 0.35 V and E = 0.49 V) and one cathodic peak ( E = 0.28 V) attributed to the UPD H; the UPD H occurs in the entire 0.10–0.55 V range; in the case of the Pd NOs, broad waves with weakly pronounced peaks also attributed to the UPD H (0.10–0.50 V); these CV characteristics are related to the shape and size of the Pd NPs; , and (iii) a small reversible feature in the 0.55–0.70 V range in the case of the Pd NOs that is assigned to the formation and reduction of a Pd surface oxide (Figure c,d). , …”

“…23,29 In the alkaline medium, the behavior is significantly different and the CV profiles reveal the following: (i) a narrow double-layer charging region with a significant current (0.55−0.70 V for the Pd NCs and 0.45−0.70 V for the Pd NOs); (ii) in the case of the Pd NCs, two anodic peaks (at E = 0.35 V and E = 0.49 V) and one cathodic peak (E = 0.28 V) attributed to the UPD H; the UPD H occurs in the entire 0.10−0.55 V range; in the case of the Pd NOs, broad waves with weakly pronounced peaks also attributed to the UPD H (0.10−0.50 V); these CV characteristics are related to the shape and size of the Pd NPs; 18,32 and (iii) a small reversible feature in the 0.55−0.70 V range in the case of the Pd NOs that is assigned to the formation and reduction of a Pd surface oxide (Figure 2c,d). 26,33 Any eventual application of shape-controlled Pd NPs (here, Pd NCs and Pd NOs) depends on their stability. Consequently, we examined their behavior by conducting CV measurements (repetitive potential cycling experiments) in the potential range of the UPD H (Figure 3a,b) and the H absorption and desorption (Figure 3c,d).…”

Manganese Oxides (Mn3O4 & α‐MnO2) as Co‐catalysts in Pd‐Based Nanomaterials for the Ethylene Glycol Electro‐Oxidation.

“…The electrochemical profiles in alkaline medium (0.5 M KOH) demonstrated that each metal oxide provided different features. For Pd/α-MnO 2 (Figure 6a), the cyclic voltammogram (CV) revealed the presence of at least four peaks; the labeled peak I found at À 0.4 V vs. NHE can be related to the anion adsorption, [27] while peaks III and IV are related to the formation of Pd oxides and to their respective reduction. [28] Peak II (located at 0.05 V vs. NHE) is too far from the adsorption zone of OH À species on Pd surfaces (from À 0.6 to À 0.3 V vs. NHE) and from the zone related to the formation of Pd oxides.…”

Subsurface Hydride Formation Leads to Slow Surface Adsorption Processes on a Pd(111) Single-Crystal Electrode in Acidic Electrolytes

“…Electrochemical characterization of Pd single-crystal electrodes started after the introduction of the inductive heating technique. , Hoshi et al carried out a considerable amount of work on Pd single-crystal electrodes with low- and high-index planes to explore (bi)­sulfate anion adsorption , and CO adsorption processes by infrared reflection absorption spectroscopy (IRAS). Later, they continued with a series of systematic experiments to describe the cyclic voltammograms of Pd-stepped electrodes. − All studies specifically focused on the effect of introducing different types of steps with different step densities, on voltammetric peaks in the more positive potential region (0.65 V < E < 1.20 V) related to hydroxide/oxide formation on Pd surfaces. However, cycling to such high potentials always induces irreversibility in the subsequent cycles, suggesting that the formation of O ads is accompanied by a significant restructuring of the Pd surface.…”