Title: Air-Stable Calcium Cyanamide-Supported Ruthenium Catalyst for Ammonia Synthesis and Decomposition

Abstract

Efficient ammonia synthesis and decomposition processes under mild conditions are important to meet the expanding demand in major applications of ammonia as the energy carrier and to provide feedstock for chemical industry. In this study, we report that air-stable calcium cyanamide-supported ruthenium (Ru/CaCN₂) works as an efficient and stable catalyst for ammonia synthesis and decomposition. Ru/CaCN₂ exhibits greater catalytic performances for both reactions than Ru/Ca₂N electride and Ru–Cs/MgO. The kinetic analysis for ammonia synthesis suggests that Ru/CaCN₂ exhibits low apparent activation energy and high resistance to hydrogen poisoning, which has characteristics similar to the kinetic parameters of Ru-supported electride catalyst. H₂-temperature programmed reaction and temperature programmed desorption revealed that Ru promoted the formation of CN₂ vacancies on the CaCN₂ surface which in turn capture hydrogen as H^– ions during the reaction. Density functional theory calculations provide insights into how the formation of CN₂ vacancies is promoted by Ru, which leads to the decrease in the work function of the CaCN₂ surface and the hydrogen capture at the Ru-support interface. These results suggest that the high catalytic performance of Ru/CaCN₂ can be attributed to the formation of a quasi-electride structure at the Ru–CaCN₂ interface.

Authors:

Kishida, Kazuhisa  ^[1];

• Search DOE PAGES for author "Kishida, Kazuhisa"
• Search DOE PAGES for ORCID "0000-0002-0875-8874"

Kitano, Masaaki  ^[2];

• Search DOE PAGES for author "Kitano, Masaaki"
• Search DOE PAGES for ORCID "0000-0003-4466-7387"

Sasase, Masato ^[1]; Sushko, Peter V.  ^[3];

• Search DOE PAGES for author "Sushko, Peter V."
• Search DOE PAGES for ORCID "0000-0001-7338-4146"

Abe, Hitoshi  ^[4];

• Search DOE PAGES for author "Abe, Hitoshi"
• Search DOE PAGES for ORCID "0000-0001-6970-3642"

Niwa, Yasuhiro ^[5]; Ogasawara, Kiya ^[1]; Yokoyama, Toshiharu ^[1]; Hosono, Hideo  ^[1]

• Search DOE PAGES for author "Hosono, Hideo"
• Search DOE PAGES for ORCID "0000-0001-9260-6728"

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+ Show Author Affiliations

1. Tokyo Inst. of Technology, Yokohama (Japan). Materials Research Center for Element Strategy
2. Tokyo Inst. of Technology, Yokohama (Japan). Materials Research Center for Element Strategy; Japan Science and Technology Agency (JST), Saitama (Japan). PRESTO
3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical Sciences Division
4. High Energy Accelerator Research Organization (KEK), Tsukuba (Japan). Inst. of Materials Structure Science; SOKENDAI (The Graduate Univ. for Advanced Studies), Tsukuba (Japan). Dept. of Materials Structure Science; Ibaraki Univ. (Japan). Graduate School of Science and Technology
5. High Energy Accelerator Research Organization (KEK), Tsukuba (Japan). Inst. of Materials Structure Science

Publication Date:

Tue Jun 23 00:00:00 EDT 2020

Research Org.:

Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE Laboratory Directed Research and Development (LDRD) Program; Japan Science and Technology Agency (JST); Japan Society for the Promotion of Science (JSPS)

OSTI Identifier:

1673585

Report Number(s):

PNNL-SA-154003
Journal ID: ISSN 2574-0962

Grant/Contract Number:  

AC05-76RL01830; JPMJPR18T6; JP19H05051; JP19H02512; 17H06153

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Energy Materials

Additional Journal Information:

Journal Volume: 3; Journal Issue: 7; Journal ID: ISSN 2574-0962

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; ammonia synthesis; ammonia decomposition; ruthenuim; electride; calcium cyanamide