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 delta-MoC(001). For the supported Au4 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 Au4 cluster while the second H atom is transferred to the support. In contrast, for Au-4/VC(001) and Au-4/delta-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.