The adsorption of pyridine on Au(111) single crystal electrodes has been systematically studied in a broad range of pH values between 1 and 13. From the voltammetric features of Au(111) in 0.1 M pyridine a potential/pH diagram has been derived, which classifies various phases for adsorbed pyridine. At sufficiently high concentrations of unprotonated pyridine in solution, a significantly enhanced activity for formic acid oxidation on Au( 111) is observed in a narrow potential region, where strongly bound formate has not yet reached its saturation coverage. The various pyridine structures exhibit different enhancement factors. At positive potentials, the typical features of formic acid oxidation on Au(111) are present, pointing toward complete replacement of adsorbed pyridine by formate.

To obtain fundamental insights into the performance of polymer electrolyte membrane (PEM) fuel cells, we perform a parallel investigation of the influence of platinum surface oxide (PtO) formation on the electrocatalytic activity toward the oxygen reduction reaction (ORR) for a polycrystalline platinum electrode in comparison with a commercial PEM fuel cell. PtO is formed by holding both systems at a constant potential for a given period of time. Conditioning potentials between 0.5 and 1.0 V versus SHE and conditioning times from 5 s up to 10 h are explored, respectively. We find that the voltage difference of the ORR between the oxidized and oxide‐free states depends on both the conditioning potential as well as the conditioning time at a given potential and furthermore increases with the applied target current. The change of the voltage loss over time, the so‐called voltage loss rate α, shows a maximum at potentials between 0.85 and 0.9 V and increases with increasing current density. We discuss various hypotheses to explain these findings obtained by linear voltammetry, Tafel slope analysis, Auger electron spectroscopy, and atomic force microscopy experiments. Finally, we conclude that the voltage loss rate is influenced by changes in the relative electrocatalytic activity of different crystal facets for the ORR as the oxide coverage varies.

This study presents a green and facile technique for producing micro/nano‐structured and porous Cu electrodes via in‐liquid plasma electrolysis using phosphorous‐oxoanion‐based electrolytes. The Cu electrodes exhibit unique surface structures, including octahedral nanocrystals besides nanoporous and microporous structures, depending on the employed electrolyte. The incorporation of P‐atoms into the Cu surfaces is observed. The resulting Cu electrodes have increased roughness, leading to higher current densities for CO2 electroreduction reaction. The selectivity of the modified Cu electrodes towards C2 products is highest for the Cu electrodes treated in Na2HPO3 and Na3PO4 electrolytes, while those treated in Na2H2PO2 produce the most H2. The Cu electrode treated in Na3PO4 produces ethylene (23%) at –1.1 V vs. RHE, and a comparable amount of acetaldehyde (15%) that is typically observed for Cu(110) single crystals. The enhanced selectivity is attributed to several factors, including the surface morphology, the incorporation of phosphorus into the Cu structure, and the formation of Cu(110) facets. Our results not only advance our understanding of the influence of the electrolyte’s nature on the plasma electrolysis of Cu electrodes, but also demonstrates that in‐liquid plasma treatment and phosphorous‐doping of Cu surfaces hold promise for the development of efficient Cu electrocatalysts for sustainable CO2 conversion.