From previous work within the group, the design of highly active binary borides VB2 and MoB2 catalysts for hydrogen production was reported1-2. Using the Gibbs free energy of hydrogen (ΔGH) binding onto the surface as the descriptor, density functional theory (DFT) calculations on surface slab models were used to predict a negative ΔGH for VB2 in the mixed V/B terminated {101} layer while for the {101} layer of MoB2 the ΔGH crosses zero and is positive, at high hydrogen coverages. Now based on these results the ternary solid solution phases of MoxVx-1B2 (x=0.1, 0.3, 0.5, 0.7, and 0.9) were synthesized and experimental measurements of their Hydrogen evolution reaction (HER) activity in acid electrolytes revealed an increase in activity with increasing Mo content with the trend peaking for Mo0.7V0.3B2 before decreasing. In this work we will present on the DFT calculations on the {110} and {101} mixed V/B terminated layers of Mo0.75V0.25B2 and Mo0.5V0.5B2 to study the active sites of these materials. In conjunction with the HER activity trend for the solid solution, it was also experimentally found that the c lattice parameter also followed the same trend of increasing with Mo content to a maximum for Mo0.7V0.3B2 before decreasing. In the next part of this study, the density of state (DOS) and Crystal Orbital Hamilton Populations (COHP) of the two surface slab models along with MoB2 and VB2 will be done to study the relationship between their electronic structures and bonding properties of these binary and ternary borides to HER activity.

DFT studies on the HER activity, electronic structure, and bonding properties of the boride MoxVx-1B2 (0 < x < 1)

ACS Spring 2022

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