Rest Potentials in the Platinum-Oxygen-Acid System

Abstract

The rest potential of a platinum bead electrode in oxygen-stirred acid solution was investigated as a function of the pH, the partial pressure of oxygen, and the history of electrode preparation. It is believed that the theoretical equilibrium oxygen potential, +1.229v vs. N.H.E., cannot be obtained in any ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 131.215.225.9 Downloaded on 2015-05-28 to IP Vol. 109, No. 9 REST POTENTIALS bottom of each inlet tube is placed a ball of platinum gauze to break the gas stream into fine bubbles. Finally, a small hole, through which a thin platinum wire may be inserted as a pre-electrolysis electrode, is made in each top. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 131.215.225.9 Downloaded on 2015-05-28 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 131.215.225.9 Downloaded on 2015-05-28 to IP Vol. 109, No. 9 REST POTENTIALS IN Pt-O-ACID SYSTEM 865When these substances are present the system becomes more reversible.

Improved Internal Reference Oxygen Sensors with Composite Ceramic Electrodes

“…formation of the peroxide ion, might be the dominant reaction with a much lower equilibrium voltage, similar to the low open circuit voltage observed in low temperature fuels cells like the polymer electrolyte membrane fuel cell (PEMFC). 46,47 Cell performance.-The cell responds to pO 2 variations rapidly as shown in Figure 5. The volume of the test setup is ca.…”

PEM fuel cell open circuit voltage (OCV) in the temperature range of 23°C to 120°C

“…The difference between the theoretical and measured OCVs is mainly caused by two different drops in potential ( E OCV Pt−O 2 and E OCV H 2 −xover as listed in Table 2). One drop ( E OCV Pt−O 2 ) is caused by a reaction between the Pt surface and O 2 , resulting in a mixed cathode potential (E OCV mixed ) [12,[18][19][20]35], and the other drop ( E OCV H 2 −xover ) is caused by H 2 crossover from the anode to cathode, reacting with O 2 reducing the O 2 surface concentration, resulting in a decrease in the E r c value by an amount equivalent to E OCV H 2 −xover . For a mixed cathode potential, a local-cell mechanism has been put forward to explain the Pt-O 2 reaction mechanism at the electrode in an O 2 saturated acidic solution [18,35,40,41].…”

“…A mixed potential [15][16][17][18] was widely used to interpret the lower open circuit voltage in an acidic medium, when compared to the thermodynamic value of the oxygen electrode (about 1.23 V versus NHE at 25 • C). This mixed potential is a result of the cathodic four-electron oxygen reduction reaction (ORR), and the anodic oxidation that is considered to be either Pt oxidation [18] or the oxidation of impurities [15]. Parthasarathy et al [12,19,20] employed a micro Pt electrode coated with a thin Nafion membrane, which is similar to a fuel cell cathode/membrane environment, and observed behaviour of the open circuit voltage.…”

Oxygen-Containing Nanoclusters on the Surface of Pt-Electrodes and Oxygen Reduction Reaction in Alkaline Medium

“…Therefore, a "mixed potential" with some intermediate value in the 0.9 to 1.23 V range should be observed on Pt-electrodes. The stationary potential with values within narrow 1.17-1.16 V (versus RHE) interval was observed in experimental studies [23,24]; it was explained by the studies' author as manifestation of the "mixed potential". Let us note that potential of cathodic reaction (2) remains practically unchanged value in a course of reaction (11) in the oxygen atmosphere.…”

“…As a result, the averaged potential, mix , at which reaction (11)) may proceed is established. Similar methods of calculation of parameter mix ("mixed potential") were used in studies [23,24] for investigation of stationary potentials on Ptelectrodes in 2 N H 2 SO 4 . The studies' author assumed that platinum surface is not inert in relation to molecular oxygen and that reaction Pt-O + 2H + + 2e − ↔ Pt + H 2 O is realized in acidic solutions.…”