Molecular catalysts for the hydrogen evolution reaction: a first-principles study

Molecular catalysts can be used in solution to promote the hydrogen evolution reaction (HER) during electrolysis and photocatalysis processes. We study the HER from first principles for four different molecular catalysts composed of a transition metal atom and two organic ligands. By computing the Gibbs free energy from density functional theory (DFT) at every step of the HER, we identify the protonation sites and the most favourable catalytic pathway on the different catalysts. We compare the efficiency of the different catalyst from their energetic span and from their Pourbaix diagrams, which shows the electrical potential and pH at which the HER becomes spontaneous. We find that both the copper and nickel based systems offer a viable alternative for HER molecular catalysts free of precious metals.