Theoretical insights into the generation and reactivity of hydride on the ZnO(10
0) surface†
Abstract
ZnO is an important catalytic material for CO/CO2 hydrogenation. In this work, the pristine ZnO(100) and the surfaces with Zn–O dimer vacancies (ZnO(10
0)–(Zn–O)DiV) and oxygen vacancies are calculated. We find that the hydride (H−) species can be generated via heterolytic H2 dissociation on these surfaces, and that ZnO(10
0)–(Zn–O)DiV only needs to overcome the energy barrier of ∼0.10 eV. This is because the ZnO system has flexible orbitals for electron storage and release and the low-coordinated Zn3c atoms at the defect sites can form stable Zn–H− covalent bonds with high symmetry. Flexible Zn orbitals also impart the unique feature of activating multiple electrophilic adsorbates simultaneously as excess electrons exist. Moreover, we show that the covalent Zn–H− species can regulate the catalytic activity and selectivity for CO2 hydrogenation by preferentially producing *HCOO intermediates at Zn–O dimer vacancies. These results may help in the design of efficient Zn-based hydrogenation catalysts.