On the dissociation of molecular hydrogen by Au supported on transition metal carbides: choice of the most active support.

A systematic density functional study of the adsorption and dissociation of H(2) on the clean (001) surface of various transition metal carbides (TMCs; TM = Ti, Zr, V, Mo) and on Au(4) nanoclusters supported on these TMCs is presented. It is found that the H(2) dissociation on the bare clean TMCs strongly depends on the chemical nature of the support. Thus, the H(2) molecule interacts rather strongly with TiC(001) and ZrC(001) but very weakly with VC(001) and δ-MoC(001). For the supported Au(4) cluster, two different types of molecular mechanisms are found. For Au(4)/TiC(001) and Au(4)/ZrC(001), H(2) dissociation leads to a H atom directly interacting with the Au(4) cluster while the second H atom is transferred to the support. In contrast, for Au(4)/VC(001) and Au(4)/δ-MoC(001), both H atoms interact with the Au(4) cluster. Overall, the present study suggests that, among the systems studied, Au/ZrC is the best substrate for H(2) dissociation.