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

Abstract

A systematic density functional study of the adsorption and dissociation of H₂ on the clean (001) surface of various transition metal carbides (TMCs; TM = Ti, Zr, V, Mo) and on Au₄ nanoclusters supported on these TMCs is presented. It is found that the H₂ dissociation on the bare clean TMCs strongly depends on the chemical nature of the support. Thus, the H₂ molecule interacts rather strongly with TiC(001) and ZrC(001) but very weakly with VC(001) and δ-MoC(001). For the supported Au₄ cluster, two different types of molecular mechanisms are found. For Au₄/TiC(001) and Au₄/ZrC(001), H₂ 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 Au₄/VC(001) and Au₄/δ-MoC(001), both H atoms interact with the Au₄ cluster. Overall, the present study suggests that, among the systems studied, Au/ZrC is the best substrate for H₂ dissociation.