On the interaction of Mg with the (111) and (110) surfaces of ceria

The catalytic activity of cerium dioxide can be modified by deposition of alkaline earth oxide layers or nanoparticles or by substitutional doping of metal cations at the Ce site in ceria. In order to understand the effect of Mg oxide deposition and doping, a combination of experiment and first principles simulations is a powerful tool. In this paper, we examine the interaction of Mg with the ceria (111) surface using both angle resolved X-ray (ARXPS) and resonant (RPES) photoelectron spectroscopy measurements and density functional theory (DFT) corrected for on-site Coulomb interactions (DFT + U). With DFT + U, we also examine the interaction of Mg with the ceria (110) surface. The experiments show that upon deposition of Mg, Ce ions are reduced to Ce3+, while Mg is oxidised. When Mg is incorporated into ceria, no reduced Ce3+ ions are found and oxygen vacancies are present. The DFT + U simulations show that each Mg that is introduced leads to formation of two reduced Ce3+ ions. When Mg is incorporated at a Ce site in the (111) surface, one oxygen vacancy is formed for each Mg to compensate the different valencies, so that all Ce ions are oxidised. The behaviour of Mg upon interaction with the (110) surface is the same as with the (111) surface. The combined results provide a basis for deeper insights into the catalytic behaviour of ceria-based mixed oxide catalysts

On the interaction of Mg with the (111) and (110) surfaces of ceria

The catalytic activity of cerium dioxide can be modified by deposition of alkaline earth oxide layers or nanoparticles or by substitutional doping of metal cations at the Ce site in ceria. In order to understand the effect of Mg oxide deposition and doping, a combination of experiment and first principles simulations is a powerful tool. In this paper, we examine the interaction of Mg with the ceria (111) surface using both angle resolved X-ray (ARXPS) and resonant (RPES) photoelectron spectroscopy measurements and density functional theory (DFT) corrected for on-site Coulomb interactions (DFT + U). With DFT + U, we also examine the interaction of Mg with the ceria (110) surface. The experiments show that upon deposition of Mg, Ce ions are reduced to Ce3+, while Mg is oxidised. When Mg is incorporated into ceria, no reduced Ce3+ ions are found and oxygen vacancies are present. The DFT + U simulations show that each Mg that is introduced leads to formation of two reduced Ce3+ ions. When Mg is incorporated at a Ce site in the (111) surface, one oxygen vacancy is formed for each Mg to compensate the different valencies, so that all Ce ions are oxidised. The behaviour of Mg upon interaction with the (110) surface is the same as with the (111) surface. The combined results provide a basis for deeper insights into the catalytic behaviour of ceria-based mixed oxide catalysts

Tunable Energy Release in a Reversible Molecular Solar Thermal System br

Molecular solar thermal (MOST) systems open application fields for solar energy conversion as they combine conversion, storage, and release in one single molecule. For energy release, catalysts must be controllable, selective, and stable over many operation cycles. Here, we present a MOST/catalyst couple, which combines all these properties. We explore solar energy storage in a tailor-made MOST system (cyano-3-(3,4-dimethoxyphenyl)-norbornadiene/quadricyclane; NBD \u27/QC \u27) and the energy release heterogeneously catalyzed at a Au(111) surface. By photoelectrochemical infrared reflection absorption spectroscopy (PEC-IRRAS) and scanning tunneling microscopy, we show that Au triggers the energy release with very high activity. Most remarkably, the release rate of the heterogeneously catalyzed process can be tuned by applying an external potential. Our durability tests show that the MOST/catalyst system is stable over 1000 storage cycles without any decomposition. The surface structure of the catalyst is preserved, and its activity decreases by only 0.1% per storage cycle