DFT Study of the BH₄⁻ Hydrolysis on Au(111) Surface

Abstract

The mechanism of the catalytic hydrolysis of BH4− on Au(111) as studied by DFT is reported. The results are compared to the analogous process on Ag(111) that was recently reported. It is found that the borohydride species are adsorbed stronger on the Au0‐NP surface than on the Ag0‐NP surface. The electron affinity of the Au is larger than that of Ag. The results indicate that only two steps of hydrolysis are happening on the Au(111) surface and the reaction mechanism differs significantly from that on the Ag(111) surface. These remarkable results were experimentally verified. Upon hydrolysis, only three hydrogens of BH4− are transferred to the Au surface, not all four, and H2 generation is enhanced in the presence of surface H atoms. Thus, it is proposed that the BH4− hydrolysis and reduction mechanisms catalyzed by M0‐NPs depend considerably on the nature of the metal.

Hydrogen adsorption on various transition metal (111) surfaces in water: a DFT forecast

“…S1, ESI† 35–37,59 ), that didn’t consider solvation effects, the hydrogen binding energies are higher than other published results. 13…”

“…The hydrogen binding energies on the metal surfaces is compared with the previous studies and the values are in line with the reported values (Table S2, ESI† 31,34 ), though, they are higher than the reported values due to the differences in the computational methods used. 13…”

“…Recent studies have shown that the presence of co-adsorbed species and charge on metal surfaces affects the electronic structure of the metal and adsorption energies. 12,13,90,91 In this study, the hydrogen adsorption energies are calculated using the implicit solvation model, VASPsol, 77 to include the effect of the aqueous medium. In addition to that, a water molecule which is adsorbed through the oxygen atom on the atop site is added to the metal surface.…”

“…It should be noted that in many catalytic processes the H atoms stem from the water after a negative charge is formed on the metal, e.g. : electrocatalytic processes, 8,28,55 reactions with radicals, 18,21,22 reactions with BH 4 − 12,13 etc. Negative or positive ion metal surfaces, with one excess electron or one missing electron, using Na + or Cl − as a counter ion were evaluated.…”

“…3 Materials that are precursors of H 2 are widely explored, the most studied material is H 2 O, 4–8 but other materials e.g. : BH 4 − , 9–13 NH 3 (NH 4 + ) 14,15 are also intensively studied. Transition metals are used as important catalysts for many of the hydrogen evolution reactions.…”