Copper oxide, surface reduction through

When a simple galvanic cell does useful work, it is called a battery. If the external circuit is connected with a wire, electrons flow from the site of oxidation at the magnesium strip and through the LED to the surface of the copper strip, where reduction of Cu + ions takes place. The voltage pushes electrons through the LED, causing it to light up. 

Because of the excellent catalytic performance of the ceria-based C03O4 and CuO catalysts, a combination of the two systems was investigated by preparing, through co-precipitation, mixed Cu-Co-Ce-O oxides with different compositions. The mixed oxides had a larger surface area with respect to the Co-Ce-O and Cu-Ce-O composite oxides. Moreover, the addition of cobalt to the Cu-Ce-O catalyst enhanced thermal stability because the particle size was unchanged on calcination at 850 °C. According to the H2-TPR patterns, the peaks due to cobalt oxide reduction and those for copper oxide reduction were reciprocally affected and shifted towards lower temperatures. The interaction between cobalt and... 

As a result of that reductive process, a deposit of copper metal (denoted in Eq. 2.2 by s for solid ) is formed on the carbon electrode surface. The prominent anodic peak recorded in the reverse scan corresponds to the oxidative dissolution of the deposit of copper metal previously formed. The reason for the very intense anodic peak current is that the copper deposit is dissolved in a very small time range (i.e., potential range) because, in the dissolution of the thin copper layer, practically no diffusion limitations are involved, whereas in the deposition process (i.e., the cathodic peak), the copper ions have to diffuse through the expanding diffusion layer from the solution to the electrode surface. These processes, labeled as stripping processes, are typical of electrochemically deposited metals such as cadmium, copper, lead, mercury, zinc, etc., and are used for trace analysis in solution [84]. Remarkably, the peak profile is rather symmetrical because no solution-like diffusive behavior is observed. 

In Equation 9.13, Zi, and Z2 are the number of electrons involved for redox Reaction 9.1 and 9.2, respectively, and F is Faraday s constant. If AG is negative then the oxidized form, Ox], will be reduced by the reductant, Red2. As an example, Pt can be readily deposited onto Cu surfaces and onto Au [97]. Deposition of Pt onto pre-reduced Ru surfaces has also been carried out using flic same principles. Similarly, Ru has been deposited onto Cu surfaces, but to a smaller extent than Pt and Au. This is in fact seen experimentally, by preferential Ru deposition onto the rims of copper particles [97]. The equilibrium potentials, Ei and E2, are given by the metal and metal-salt involved, as defined by Nemst s law. It follows that the anion of the metal salt influences the E value and hence, AG. Through the selection of proper complexing ions it is possible to reverse the host and depositing metals. This has been shown for Pd deposition onto Rh surfaces... 

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