Key Role of Anionic Doping for H2 Production from Formic Acid on Pd(111)

Hydrogen evolution by the catalytic decomposition of formic acid in solution is a key reaction for hydrogen storage for which palladium is one of the most efficient catalysts. Based on density functional theory (DFT) computations, we explain why the presence of an anionic promoter renders palladium more active and more selective for formic acid dehydrogenation. The promotion is well-captured by modeling the anion by a negatively charged surface. This promotional effect can be traced back to the modulation of the electric field at the catalyst surface, with a strongly contrasted action on the energy of the various species along the competing pathways through the electrostatic interaction between the electric field and the surface dipole moment. As a result, both the reaction kinetics and selectivity are markedly improved. This opens the door to a rational design of catalytic systems using promoters.