【公開日：2025.06.10】【最終更新日：2025.05.19】

課題データ / Project Data

課題番号 / Project Issue Number

24AE0001

利用課題名 / Title

Research of the strong metal-support interaction involving low melting point metals in reverse water gas shift reaction

利用した実施機関 / Support Institute

日本原子力研究開発機構 / JAEA

機関外・機関内の利用 / External or Internal Use

外部利用/External Use

技術領域 / Technology Area

【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-

【重要技術領域 / Important Technology Area】（主 / Main）革新的なエネルギー変換を可能とするマテリアル/Materials enabling innovative energy conversion（副 / Sub）-

キーワード / Keywords

Liquid metals, RWGS reaction, CO2 conversion, strong metal-support interaction

利用者と利用形態 / User and Support Type

利用者名（課題申請者）/ User Name (Project Applicant)

Wu Dongshuang

所属名 / Affiliation

Nanyang Technological University

共同利用者氏名 / Names of Collaborators Excluding Supporters in the Hub and Spoke Institutes

Huayu Gu,Bing Zhu,Yuanyuan Wang,Masashi Nakamura

ARIM実施機関支援担当者 / Names of Supporters in the Hub and Spoke Institutes

松村　大樹

利用形態 / Support Type

（主 / Main）共同研究/Joint Research（副 / Sub）-

利用した主な設備 / Equipment Used in This Project

AE-006：エネルギー分散型XAFS装置

報告書データ / Report

概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)

For the loaded NPs, we found that the liquid metals can form metal-oxygen bonds from the support even at room temperature. At high temperatures, the diffusion of liquid metals can cause the formation of Intermetallic compounds, the real active species for CO₂ hydrogenation. The catalysts can achieve over 99% CO conversion and enhanced CO yields under reaction conditions. The transformation process and structural changes of catalysts can be characterized by XAFS.

実験 / Experimental

Experimental conditions and beamtime:
1. X-ray energy calibration of Ni K-edge using Si 111 monochromator and In K-edge using Si 311 monochromator.
2. Chamber set-up and gas system set-up.
3. Edge jump check and sample preparation.
4. For In and Ni K-edge of In/NiO before and after calcination under Ar atmosphere: XAFS measurements at RT and 350 ºC under Ar atmosphere.
5. For In and Ni K-edge of samples (including In/NiO, In/NiO-T catalysts) under CO₂/H₂ atmosphere at 400 ºC:
(1) Warming process: 0.5 h
(2) Cooling to 50 ºC: 0.5 h
(3) XAFS measurement at 450 ºC. Conduct six consecutive tests.

結果と考察 / Results and Discussion

The coordination structures of In species before and after calcination under Ar atmosphere were further compared by XAFS. The In K-edge EXAFS spectrum of In/NiO revealed the presence of In-O bonds (Fig. 1a), suggesting that In maybe extracted lattice oxygen from the NiO surface during preparation. Notably, the In-O bond length in the In/NiO catalyst was shorter than that of standard In₂O₃, and no characteristic peaks attributed to the In-O-In bond were observed within the 2-4 Å range, demonstrating that the In atoms were randomly dispersed on the NiO surface and bonded with oxygen atoms. Compared to In/NiO, In/NiO-T exhibited the decreased In-O peak intensity and shortened In-O bond length in the EXAFS spectra, implying a reduced average In-O coordination number and potentially stronger confinement of In atoms within the NiO crystal structure after calcination. Additionally, according to Ni K-edge EXAFS spectra of In/NiO and In/NiO-T, the average Ni-O coordination number of In/NiO-T maintained stable after calcination, indicating that metallic In primarily affected the NiO surface structure (Fig. 1b). Thus, metal In can be uniformly dispersed on the NiO surface through melting, migration and bonding, forming abundant In/NiO interfaces.
 To probe the hyperfine structure of In and Ni species in In/NiO-T catalyst during the reaction, in-situ XAFS measurements were performed at 400 °C under CO₂/H₂ atmosphere. According to the In K-edge EXAFS spectra (Fig. 2a), the In-O bond disappeared rapidly, and a new peak appeared at 2.2 Å, which could be attributed to the formation of In-Ni bonds based on our XRD results. Subsequently, Ni K-edge EXAFS spectra of NiO and In/NiO-T catalysts showed a progressive decrease in the Ni-O-Ni peak intensity and a corresponding increase in the Ni-Ni peak intensity, suggesting the reduction of NiO to metallic Ni (Fig. 2b, 2c).
 By fitting the XANES spectra to track the change in the average valence state of Ni over time, the reduction rate of NiO in the In/NiO-T catalyst was initially rapid but then slowed, whereas the reduction rate of pristine NiO remained stable (Fig. 3). This disparity may be attributed to the inductive effect of In species, which extracted lattice oxygen from the NiO surface, accelerating its reduction process. The generated In-O-Ni bonds exhibited higher lattice oxygen stability than Ni-O-Ni bonds. Consequently, the In-O-Ni bonds may inhibit the full reduction of NiO, affecting the generation of active hydrogen species and mitigating the over-hydrogenation of CO.
  

図・表・数式 / Figures, Tables and Equations

Fig. 1 (a) In K-edge and (b) Ni K-edge EXAFS spectra of 15%In/NiO and 15%In/NiO-T.

Fig. 2 (a) In situ In K-edge EXAFS spectra of In/NiO-T. In situ Ni K-edge EXAFS spectra of (b) In/NiO-T and (c) NiO. (Reaction conditions: CO₂:H₂=1:3, 80 mL/min, P = 0.1 MPa, 400 ℃).

Fig. 3 In situ Ni K-edge XANES spectra of (a) NiO and (b) In/NiO-T at 400 ℃ under CO₂/H₂ atmosphere. (c) The Ni valence change during the reaction determined by XANES linear combination fitting.

その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)

成果発表・成果利用 / Publication and Patents

論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)

口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.

特許 / Patents

特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件