Hydrogen donation of bio-acids over transition metal facets: a density functional theory study

Bio-acids produced from biomass fast pyrolysis are regarded as alternative hydrogen source for upgrading bio-oil into transport fuels. In this work, the hydrogen donation performance of acetic acid (AcOH) and formic acid (FA) were evaluated over the transition metal facet in comparison with H₂ gas, using Density Functional Theory (DFT) modelling. It was revealed that Mo (110) led to stronger binding with the bio-acid molecule than other base transition metals, and the consequent electrons migration significantly facilitated the bio-acids decomposition. AcOH exhibited a greater potential than FA as a hydrogen donor over Mo (110) because it released more H atoms with low energy barriers. H₂ gas showed undoubtable merits of dissociative adsorption with negligible energy barrier over Mo (110). However, the larger enthalpy changes from the exothermic decomposition of bio-acids would probably more facilitate the activation and migration of the individual H atoms for their donation compared to H₂ gas.