The Bifurcation Point of the Oxygen Reduction Reaction on Au-Pd Nanoalloys

The oxygen reduction reaction is of major importance in energy conversion and storage. Controlling electrocatalytic activity and its selectivity remains a challenge of modern electrochemistry. Here, first principle calculations and analysis of experimental data unravel the mechanism of this reaction on Au-Pd nanoalloys in acid media. A mechanistic model is proposed from comparison of electrocatalysis of oxygen and hydrogen peroxide reduction on different Au-Pd ensembles. A H2O production channel on contiguous Pd sites proceeding through intermediates different from H2O2 and OOHσ adsorbate is identified as the bifurcation point for the two reaction pathway alternatives to yield either H2O or H2O2. H2O2 is a leaving group, albeit reduction of H2O2 to H2O can occur by electrocatalytic HO-OH dissociation that is affected by the presence of adsorbed OOHσ. Similarities and differences between electrochemical and direct synthesis from H2 + O2 reaction on Au-Pd nanoalloys are discussed

Enhanced electrolytic generation of oxygen gas at binary nickel oxide–cobalt oxide nanoparticle-modified electrodes

This study addresses the enhancement of the oxygen evolution reaction (OER) on glassy carbon, Au, and Pt electrodes modified with binary catalysts composed of nickel oxide nanoparticles (nano-NiOx) and cobalt oxide nanoparticles (nano-CoOx). Binary NiOx/CoOx-modified electrodes (with NiOx initially deposited) show a high catalytic activity and a marked stability which far exceeds that obtained at the individual oxide-modified electrodes. This enhancement is demonstrated by a marked negative shift (more than ca. 600 mV) in the onset potential of the OER compared to that obtained at the unmodified electrodes. The modified electrodes show a significantly higher long-term stability, over a period of 5 h of continuous electrolysis, without any significant loss of activity towards the OER in alkaline medium. The influence of the solution pH, the loading level, and sequence of deposition of each oxide on the electrocatalytic activity of the modified electrodes is addressed with an aim to maximize the catalytic activity of the modified electrodes towards the OER. SEM imaging is used to disclose the size and morphology of the fabricated nano-NiOx and nano-CoOx binary catalysts at the electrode surface