| Systematic study on the Ni exsolution behavior of NiAl2O4 catalysts for steam methane reforming |
| Sang-Hun Lee1, Young Jun Kwak1,2, Jae-Woo Park1, Ki-Tae Lee1,2,3 |
1Division of Advanced Materials Engineering, Jeonbuk National University, Jeonju, Jeonbuk 54896, Republic of Korea
2Hydrogen and Fuel Cell Research Center, Jeonbuk National University, Jeonju, Jeonbuk 54896, Republic of Korea
3Department of Energy Storage/Conversion Engineering of Graduate School (BK21 FOUR) , Jeonbuk National University, Jeonju, Jeonbuk 54896, Republic of Korea |
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Received: September 27, 2022; Revised: December 12, 2022 Accepted: December 20, 2022. Published online: January 4, 2023. |
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| ABSTRACT |
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The NiAl2O4 spinel exhibited a metal exsolution phenomenon to form Ni nanoparticles and nonstoichiometric Ni1−xAl2O4−x without structural collapse in a reducing atmosphere. The Ni exsolution behavior of NiAl2O4 was strongly affected by the reducing conditions, such as the reduction temperature and holding time during the reduction. The average particle size and amount of the exsolved Ni metal increased with increase in both the reduction temperature and the holding time. The re-dissolution oxidation reaction of the exsolved Ni into Ni1−xAl2O4−x to form NiAl2O4 occurred reversibly over 900 °C. The exsolved Ni nanoparticles were socketed into the surface of the reduced NiAl2O4 matrix and well dispersed without any agglomeration. Owing to this microstructure leading to an extension of the catalytic active site and suppression of agglomeration, the Ni-exsolved NiAl2O4 exhibited better steam methane reforming performance compared with the commercial Ni/Al2O3 catalyst. In addition to the improvement in catalytic activity, the Ni-exsolved NiAl2O4 showed strong tolerance for the formation of carbon due to a smaller driving force for carbon diffusion resulting from the nano-socketed structure. |
| Key words:
Hydrogen production · Steam methane reforming · Ni catalyst · Exsolution · Nickel aluminate |
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