Abstract
Ethanol steam reforming (ESR) is of societal interest. In this work, experiments were conducted to ascertain if some of the H2 is produced by a redox cycle involving H2O filling oxygen vacancies over reducible oxide catalysts. Redox cycling experiments were performed over La0.7Sr0.3MnO3-x(1 0 0) in ultra-high vacuum. It was found that H2 was produced from redox cycling with alternating ethanol and water exposures over La0.7Sr0.3MnO3-x(1 0 0), with both half-cycles occurring at temperatures ≤800 K. In the first half-cycle, ethanol ‘directly’ reduced the surface to create oxygen vacancies (not by a CO intermediate), and in the second half-cycle water filled oxygen vacancies to make H2. The H2 production during the water exposure has a half-cycle turnover frequency of >3.2 × 10-2 molecules site-1 s−1 in the temperature range of 700–800 K, which is fast enough to be part of the ESR full catalytic cycle. Flowing both reactant gases together, ethanol and water, over La0.7Sr0.3MnO3-x(1 0 0) and La0.7Sr0.3MnO3-x powders significantly increases hydrogen production compared to pure ethanol. The results suggest that steady state ESR includes a sub-mechanism of ethanol ‘directly’ reducing the surface to create oxygen vacancy, and water filling oxygen vacancy to make some of the H2 by a Mars van Krevelen type mechanism.
Original language | English |
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Article number | 156603 |
Journal | Applied Surface Science |
Volume | 617 |
DOIs | |
State | Published - Apr 30 2023 |
Funding
This research was sponsored by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science program. This research was sponsored by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science program. Thin film growth and characterization research conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan.
Funders | Funder number |
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U.S. Department of Energy | |
Office of Science | |
Basic Energy Sciences | |
Oak Ridge National Laboratory |
Keywords
- Hydrogen Production
- Mars van Krevelen
- Oxygen Vacancy
- Redox Cycling
- Steam Reforming
- Temperature Programmed Reaction
- Water Gas Shift