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Shigemoto A, Inoda Y, Ukai C, Higo T, Oka K, Sekine Y. Electric field-assisted NSR process for lean NO x reduction at low temperatures. Chem Commun (Camb) 2024; 60:1563-1566. [PMID: 38204414 DOI: 10.1039/d3cc05189g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2024]
Abstract
Lean-burn engines are gaining attention for their lower CO2 emissions, higher thermal efficiency, and improved fuel economy compared to traditional combustion engines. However, they present some difficulty for reducing nitrogen oxides (NOx) because of residual oxygen. To address this difficulty, NOx storage reduction (NSR) system, which combines noble metals and NOx adsorbents, is developed as a viable approach. But it requires cyclic operation, which adversely affects fuel efficiency. A novel approach proposed in this work is electric field-assisted lean NOx reduction, which applies an electric field to the NSR catalyst during lean conditions. This innovation uses surplus vehicle electricity for exhaust purification, enhances hydrogen transfer, and improves NOx reduction, even at low temperatures. Tests with a 3 wt% Pt-16 wt% BaO/CeO2 catalyst demonstrate markedly higher NOx conversion to N2 (13.1% vs. 2.9% without an electric field). This process is effective with extended electric field exposure, doubling the conversion rate. Electric field-assisted lean NOx reduction, by improving NSR technology, can enhance NOx conversion efficiency, reduce emissions, and optimize fuel efficiency in lean-burn engines.
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Affiliation(s)
- Ayaka Shigemoto
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
| | - Yuki Inoda
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
| | - Chihiro Ukai
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
| | - Takuma Higo
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
| | - Kohei Oka
- Isuzu Central Research Center, Fujisawa, Kanagawa, Japan
| | - Yasushi Sekine
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
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Matsuda T, Ishibashi R, Koshizuka Y, Tsuneki H, Sekine Y. Quantitative investigation of CeO 2 surface proton conduction in H 2 atmosphere. Chem Commun (Camb) 2022; 58:10789-10792. [PMID: 36093590 DOI: 10.1039/d2cc03687h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This report is the first describing a study quantitatively analysing aspects of oxide surface protonics in a dry H2 atmosphere. Elucidating surface protonics is important for electrochemical and catalytic applications. In this study, AC impedance spectroscopy was used to investigate surface conduction properties of porous CeO2 at low temperatures (423-573 K) and in a dry H2 atmosphere. Results demonstrated that the conductivity increased by several orders of magnitude when H2 was supplied. Dissociative adsorption of H2 contributes to conduction by forming proton-electron pairs. Also, H/D isotope exchange studies confirmed protons as the dominant conduction carriers. Furthermore, H2 adsorption equilibrium modelling based on the Langmuir mechanism was applied to explain the H2 partial pressure dependence of conductivity. For the first time, the obtained model explains the experimentally obtained results both qualitatively and quantitatively. These findings represent new insights into surface protonics in H2 atmosphere.
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Affiliation(s)
- Taku Matsuda
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
| | - Ryo Ishibashi
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
| | - Yoshiki Koshizuka
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
| | - Hideaki Tsuneki
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
| | - Yasushi Sekine
- Department of Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo, 169-8555, Japan.
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3
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CeO2-Based Heterogeneous Catalysts in Dry Reforming Methane and Steam Reforming Methane: A Short Review. Catalysts 2022. [DOI: 10.3390/catal12050452] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Transitioning to lower carbon energy and environment sustainability requires a reduction in greenhouse gases such as carbon dioxide (CO2) and methane (CH4) that contribute to global warming. One of the most actively studied rare earth metal catalysts is cerium oxide (CeO2) which produces remarkable improvements in catalysts in dry reforming methane. This paper reviews the management of CO2 emissions and the recent advent and trends in bimetallic catalyst development utilizing CeO2 in dry reforming methane (DRM) and steam reforming methane (SRM) from 2015 to 2021 as a way to reduce greenhouse gas emissions. This paper focus on the identification of key trends in catalyst preparation using CeO2 and the effectiveness of the catalysts formulated.
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Nakano N, Torimoto M, Sampei H, Yamashita R, Yamano R, Saegusa K, Motomura A, Nagakawa K, Tsuneki H, Ogo S, Sekine Y. Elucidation of the reaction mechanism on dry reforming of methane in an electric field by in situ DRIFTs. RSC Adv 2022; 12:9036-9043. [PMID: 35424901 PMCID: PMC8985195 DOI: 10.1039/d2ra00402j] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 03/14/2022] [Indexed: 01/17/2023] Open
Abstract
With increasing expectations for carbon neutrality, dry reforming is anticipated for direct conversion of methane and carbon dioxide: the main components of biogas. We have found that dry reforming of methane in an electric field using a Pt/CeO2 catalyst proceeds with sufficient rapidity even at a low temperature of about 473 K. The effect of the electric field (EF) on dry reforming was investigated using kinetic analysis, in situ DRIFTs, XPS, and DFT calculation. In situ DRIFTs and XPS measurements indicated that the amount of carbonate, which is an adsorbed species of CO2, increased with the application of EF. XPS measurements also confirmed the reduction of CeO2 by the reaction of surface oxygen and CH4. The reaction between CH4 molecules and surface oxygen was promoted at the interface between Pt and CeO2.
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Affiliation(s)
- Naoya Nakano
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Maki Torimoto
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Hiroshi Sampei
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Reiji Yamashita
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Ryota Yamano
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Koki Saegusa
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Ayaka Motomura
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Kaho Nagakawa
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Hideaki Tsuneki
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
| | - Shuhei Ogo
- Department of Marine Resources Science, Faculty of Agriculture and Marine Science, Kochi University Nankoku 783-8502 Japan
- Center for Advanced Marine Core Research, Kochi University Nankoku 783-8502 Japan
| | - Yasushi Sekine
- Department of Applied Chemistry, Waseda University 3-4-1, Okubo, Shinjuku Tokyo 169-8555 Japan
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5
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Torimoto M, Sekine Y. Effects of alloying for steam or dry reforming of methane: a review of recent studies. Catal Sci Technol 2022. [DOI: 10.1039/d2cy00066k] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A survey on the catalytic nature of Ni-based alloy catalysts in recent years provides a direction for future catalyst development.
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Affiliation(s)
- Maki Torimoto
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
| | - Yasushi Sekine
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan
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Murakami K, Sekine Y. Recent progress in use and observation of surface hydrogen migration over metal oxides. Phys Chem Chem Phys 2020; 22:22852-22863. [PMID: 33033817 DOI: 10.1039/d0cp04139d] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Hydrogen migration over a metal oxide surface is an extremely important factor governing the activity and selectivity of various heterogeneous catalytic reactions. Passive migration of hydrogen governed by a concentration gradient is called hydrogen spillover, which has been investigated broadly for a long time. Recently, well-fabricated samples and state-of-the-art measurement techniques such as operando spectroscopy and electrochemical analysis have been developed, yielding findings that have elucidated the migration mechanism and novel utilisation of hydrogen spillover. Furthermore, great attention has been devoted to surface protonics, which is hydrogen migration activated by an electric field, as applicable for novel low-temperature catalysis. This article presents an overview of catalysis related to hydrogen hopping, sophisticated analysis techniques for hydrogen migration, and low-temperature catalysis using surface protonics.
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Affiliation(s)
- Kota Murakami
- Applied Chemistry, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555, Japan.
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