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The nature and characteristics of the overpotential in cells of the type normalAr‐O2,H2‐H2O,normalorCO‐CO2/ZrO2‐normalCaO/O2 were determined from 700° to 1100°C over a wide range of oxygen pressures. Porous Pt black electrodes were deposited on impervious ZrO2+10 normalm/normalo false(normalmole per centfalse)normalCaO tubes. Almost pure resistance polarization is observed when normalAr‐O2 or H2‐H2O mixtures are present at the anode. However, for normalAr‐O2 mixtures dilute in O2 at the cathode, diffusion overpotential readily appears and limiting currents are eventually reached. Limiting currents, proportional to PO2 , are controlled by the diffusion of gaseous oxygen in the pores of the Pt electrode. Based on the present results and adsorption data, a mechanism is proposed for the cathode reaction. For CO‐CO2 mixtures, transition overpotential associated with the reaction CO2+2e⇄CO+O−− is observed. The transition factor is about 0.5 and exchange current densities are in the vicinity of 1 mA/cm2. Equations relating exchange current density to PCO , PCO2 , and the amount of CO adsorbed on the electrolyte are derived and compared with the experimental results. It is concluded that either gaseous or adsorbed CO and gaseous CO2 are directly involved in the electrochemical step of the reaction.

Copper−nickel−aluminum oxide solid solutions were reduced in hydrogen to produce alumina-supported copper−nickel alloy catalysts. XRD patterns of reduced oxides showed that the type of active metals which emerged upon reduction were sensitive to the reduction temperature and the copper content. Variations from +0.8 to +1 eV were found in the experimental Ni 2p3/2 binding energy (BE) of nickel in the solid solutions compared to the experimental Ni 2p3/2 BE of bulk nickel, attributed to the Ni−Ni arrangements in the solid solution. Also, when the curve-fitted BE values of Ni 2p3/2 and Cu 2p3/2 of different reduced solid solutions were compared, it was found that copper and nickel were in different chemical states depending on reduction temperature and the amount of the copper. Changes in Ni 2p3/2 BE in the reduced solid solutions were also discussed in terms of the filling of nickel d-hole bands due to nickel−copper d−d band interactions. At both high copper content and reduction temperature, copper had a tendency to segregate in order to reduce the interfacial surface energies. This was postulated based on the observation that the Ni 2p3/2 curve-fitted BE values were restored to somewhat close to bulk nickel at a copper content of 11 mol % and reduction temperature of 700 °C.

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