BH4 dissociation on various metal (1 1 1) surfaces: A DFT study

In this study, the catalytic effect of various metal surfaces on the sequential decomposition of BH₄ molecule has been studied by Density Functional Theory (DFT) for the first time. For this purpose, the sequential dissociation of BH_x (x = 0 → 4) molecules on Au, Cu, Al and Ag (1 1 1) surfaces were systematically investigated. At first, ground state structures of BH_x (x = 0 → 4) molecules and their decomposed versions such as BH_x + yH (x + y = 4) were obtained. Then, transition state search calculations were performed to find activation barriers related to every BH_x + yH (x + y = 4) decomposition step until x = 0 has been reached. An additional hydrogen atom(s) remaining from a previous step accepted as if they(it) are(is) at infinite distances from the central unit cell of the surface because it is prerequisite to form energy diagram which keeps the number of the atom(s) constant. Our calculations were supported with the lateral interaction energies and the various bond distances to clarify catalytic abilities of the surfaces. It is concluded that Au(1 1 1) surface is the most active surface among the others however the activity of the Cu(1 1 1) surface can compete with it. Al(1 1 1) and Ag(1 1 1) surfaces are the least active surfaces. This knowledge can be used to develop strategies to design Cu-based cheap and active catalyst for hydrogen generation from borohydride dissociation.