The adsorption and activation of a CO 2 molecule on cubic d-MoC(001) and orthorhombic b-Mo 2 C(001) surfaces have been investigated by means of periodic density functional theory based calculations using the Perdew-Burke-Ernzerhof exchange-correlation functional and explicitly accounting for (or neglecting) the dispersive force term description as proposed by Grimme. The DFT results indicate that an orthorhombic b-Mo 2 C(001) Mo-terminated polar surface provokes the spontaneous cleavage of a C-O bond in CO 2 and carbon monoxide formation, whereas on a b-Mo 2 C(001) C-terminated polar surface or on a d-MoC (001) nonpolar surface the CO 2 molecule is activated yet the C-O bond prevails. Experimental tests showed that Mo-terminated b-Mo 2 C(001) easily adsorbs and decomposes the CO 2 molecule. This surface is an active catalyst for the hydrogenation of CO 2 to methanol and methane. Although MoC does not dissociate C-O bonds on its own, it binds CO 2 better than transition metal surfaces and is an active and selective catalyst for the CO 2 + 3H 2 -CH 3 OH + H 2 O reaction. Our theoretical and experimental results illustrate the tremendous impact that the carbon/metal ratio has on the chemical and catalytic properties of molybdenum carbides. This ratio must be taken into consideration when designing catalysts for the activation and conversion of CO 2 .

Where oxide and metals meet: The activation of an efficient associative mechanistic pathway for the water-gas shift reaction by an oxide-metal interface leads to an increase in the catalytic activity of nanoparticles of ceria deposited on Cu(111) or Au(111) by more than an order of magnitude (see graph). In situ experiments demonstrated that a carboxy species formed at the metal-oxide interface is the critical intermediate in the reaction

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