H2 dissociation
plays crucial roles in catalytic hydrogenation
reactions and hydrogen storage. Metal-nanoparticle-based heterogeneous
catalysts often dissociate H2 via a homolytic pathway.
The heterolytic H2 dissociation pathway was identified
in several heterogeneous catalytic systems, including single-atom
catalysts, metal–support interfaces, and bulk metal oxides/sulfides/nitrides/phosphides.
The active site structures of these heterogeneous catalysts resemble
homogeneous catalysts where the metal centers (Lewis acids) are coordinated
with O/S/N/P atoms (Lewis bases). These Lewis acid–base pairs
dissociate H2 molecules heterolytically into proton–hydride
pairs, which favor the hydrogenation of polar functional groups in
unsaturated hydrocarbons. In this review, we summarize the common
structural features of heterogeneous, homogeneous, and enzyme catalysts
in the heterolytic dissociation of H2. The active sites,
Lewis acid–base pairs, are discussed throughout this review.
The energy barriers and kinetic contributions of heterolytic and homolytic
H2 dissociation pathways in heterogeneous catalytic systems
are discussed. The spectroscopic evidence of the heterolytic H2 dissociation pathways is critically reviewed.