Initial reduction of the NiO(100) surface in hydrogen
Qiang Xu1, Singfoong Cheah, Yufeng Zhao
1National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, USA.
The Journal of Chemical Physics
|July 19, 2013
Summary
Hydrogen reduction of nickel oxide (NiO) surfaces is computationally challenging. This study reveals hydrogen acts as both reactant and mediator, lowering kinetic barriers for NiO reduction and water formation on NiO(100) surfaces.
Area of Science:
- Materials Science
- Surface Chemistry
- Computational Chemistry
Background:
- Hydrogen reduction of nickel oxide (NiO) is crucial for industrial applications.
- Theoretical studies are limited due to material complexity and computational challenges.
Purpose of the Study:
- To systematically investigate the hydrogen reduction of an ideal NiO(100) surface.
- To elucidate the reaction mechanism, energetics, and kinetics using advanced computational methods.
Main Methods:
- Density Functional Theory (DFT) with Hubbard U correction.
- Verification using hybrid density functional methods.
- Analysis of surface slab models for NiO(100) reduction.
Main Results:
- Oxygen vacancies stabilize in the subsurface layer, with a high migration barrier (3.02 eV).
- Water formation and NiO reduction are favored at higher hydrogen coverage.
- Hydrogen acts as both a reactant and mediator, reducing the kinetic barrier from 2.41 eV to 1.86 eV.
Conclusions:
- The study clarifies the mechanism of hydrogen reduction on NiO(100) surfaces.
- Identified hydrogen's dual role in lowering activation energy.
- Provides theoretical insights for optimizing industrial NiO reduction processes.
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