Nondissociative Activated Dihydrogen Binding on CeO₂ Revealed by High-Pressure Operando Solid-State NMR Spectroscopy

Area of Science:

• Catalysis
• Materials Science
• Surface Chemistry

Background:

• Dihydrogen complexes are well-studied in homogeneous and enzymatic catalysis, retaining the H-H bond.
• Nondissociative chemisorbed dihydrogen binding in heterogeneous catalysis is experimentally scarce due to surface complexity and characterization challenges.

Purpose of the Study:

• To provide the first unambiguous experimental observation of activated dihydrogen binding on a reduced ceria catalyst.
• To investigate the relationship between ceria surface reduction and dihydrogen binding.
• To explore the role of bound dihydrogen in catalytic reactions.

Main Methods:

• Utilizing high-pressure operando solid-state Nuclear Magnetic Resonance (NMR) technology.
• Employing versatile NMR structural and dynamical analysis methods, including H-D through-bond coupling (JHD), T1 relaxation, and proton isotropic chemical shifts.
• Conducting in situ NMR analysis during a room-temperature ethylene hydrogenation reaction.

Main Results:

• First unambiguous experimental observation of activated dihydrogen binding on reduced ceria via surface oxygen vacancies.
• Established a proportional relationship between ceria surface reduction degree and dihydrogen binding.
• Demonstrated the participation of bound dihydrogen species in ethylene hydrogenation at room temperature.

Conclusions:

• Activated dihydrogen binding on reduced ceria is experimentally confirmed, offering insights into heterogeneous catalysis.
• The findings suggest similarities between surface-activated dihydrogen and molecular dihydrogen complexes, aiding hydrogenation mechanism understanding.
• This research has the potential to enhance hydrogen utilization in various solid catalyst systems.