(207a) The Role of Oxygen Vacancies of CeO2 Supported Catalyst on Catalytic Performance of the CO2 to CO

The performance of a catalyst depends on many factors. It is usually hard to discuss these effects separately due to their interwoven relationship. Here, we focus on the catalytic activity of nanosized Cu supported on cerium oxide by the space-confined method and mesoporous silica, whereby Cu nanocatalysts are deliberately controlled under the same loading, particle size and coordination number to highlight the interactions caused by different supports. It is interesting to note that the redox temperature of cerium oxide is dramatically decreased from >600^oC to <300^oC by CuCeOx solid solution so that its conversion is 18% with 100% selectivity approaching the equilibrium conversion 23% of the CO₂ to CO at 1 bar and 300^oC the by flow reactor.

Oxygen vacancies generated by the reducible cerium oxide were found to be able to contribute more carbonate with bidentate type absorption. The space confined method was capable of generating high Cu dispersion (~50%) from nano-size CuCeOx solid solution. The Cu maintains the CeO₂ support to keep the oxygen vacancies recycling by hydrogen spill over behavior at 300^oC when the reaction of CO₂ to CO oxidized the catalyst. However, similar metal-support was not seen in the mesopeorous silica system.

We have demonstrated that the active sites locate in the proximity between support and reduced nano-sized metal by synchrotron analysis, TEM mapping, in-situ FTIR and catalytic reaction. Furthermore, the work presented illustrates the significant role of oxygen vacancies in the metal-support interaction and how the potential of oxide supported nanocatalysts can be further explored and tuned by for the space confined method and thermal treatment for CO₂ to CO.