Comparative study on the influence of temperature, electrode potential and alloy bulk composition on hydrogen electrosorption into Pd–Pt and Pd–Au alloys

The Effect of the Iridium Alloying and Hydrogen Sorption on the Physicochemical and Electrochemical Properties of Palladium

Thin layers (up to 1 µm) of Pd-Ir alloys were electrodeposited from aqueous, galvanic baths of PdCl₂ and IrCl₃ mixtures. The morphology of the electrodeposits was examined by means of scanning electron microscopy. The composition of alloys was determined with the use of energy-dispersive spectroscopy, atomic absorption spectrometry, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. For the studies of the electrochemical properties of alloys, cyclic voltammetry, chronoamperometry, and chronopotentiometry were used. It was found that Pd-Ir alloy electrodes were surface-enriched with Pd. Pd-Ir alloys subjected to different electrochemical treatment involving hydrogen sorption changed their surface state. The continuous hydrogen sorption enhanced the Ir ions' dissolution. The values of thermodynamic functions of hydrogen sorption in strong alkaline electrolytes were comparable with those in acidic electrolytes, whereas the kinetics of the process in alkaline medium was hindered. The miscibility gap in the Pd-Ir-H system vanished for the electrode containing ca. 93.7 at.% Pd.

Application of machine-learning-based global optimization: potential-dependent co-electrosorbed structure and activity on the Pd(110) surface

Electrodes can adsorb different reaction intermediates under electrochemical conditions, which in turn significantly affect their electrochemical performance. This complex phenomenon attracts continuous interest in both science and industry for understanding the co-electrosorbed structure and activity under electrochemical conditions. Here, we report the first theoretical attempt by combining the machine-learning-based global optimization (SSW-NN method) and modified Poisson-Boltzmann continuum solvation (CM-MPB) based on first-principles calculations to elucidate the potential-dependent co-electrosorbed species on the Pd(110) surface. We reveal the potential-dependence adsorption/absorption hydrogen phases, the phase transition of α-H_ri/Pd to β-H_ri/Pd, and the co-electrosorbed H_ri-NH_y surface structures. In particular, we found that H_ri-NH₂ and H_ri-NH₃ are favorable intermediates for the N₂ reduction reaction, and the subsurface H is the key species responsible for NH₂ hydrogenation on the Pd(110) electrode.

Comparison of electrocatalytic activity of Pt1−xPdx/C catalysts for ethanol electro-oxidation in acidic and alkaline media

The Pt_1−xPd_x/C catalysts exhibit much higher electrocatalytic activity in alkaline media than in acid media.

On the Nature of Voltammetric Signals Originating from Hydrogen Electrosorption into Palladium-Noble Metal Alloys

Hydrogen sorption/desorption signals observed on cyclic voltammograms in experiments on hydrogen electrosorption into Pd-noble metal alloys (Pd-Au, Pd-Pt, Pd-Rh, Pd-Ru, Pd-Pt-Rh, Pd-Pt-Au) were characterized. The influence of electrosorption potential, scan rate and alloy bulk composition on the features of the hydrogen peaks was investigated. The experimental results were compared with those obtained on the basis of a model taken from the literature. It was confirmed that the rate of the α-β phase transition controls the overall rate of the process of hydrogen absorption/desorption into/from thin Pd-based electrodes. It was demonstrated that from the analysis of the changes of the hydrogen oxidation peak potential with the hydrogen electrosorption potential in cyclic voltammetric experiments it is possible to determine the limiting Pd bulk content, below which the β-phase in the alloy-hydrogen system is not formed.