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<p>Anion vacancies on metal oxide surfaces have been studied as either active sites or promoting sites in various chemical reactions involving oxidation/reduction processes. However, oxide materials rarely work effectively as catalysts in the absence of transition metal sites. Here we report a Ba–Si orthosilicate oxynitride–hydride as a transition-metal-free catalyst for efficient ammonia synthesis via an anion-vacancy<i>-</i>mediated mechanism. The facile desorption of H<sup>−</sup> and N<sup>3−</sup> anions plus the flexibility of the crystal structure can accommodate a high density of electrons at vacancy sites, where N<sub>2</sub> can be captured and directly activated to ammonia through hydrogenation processes. The ammonia synthesis rates reach 40.1 mmol g<sup>−1</sup> h<sup>−1</sup> at 300 °C by loading ruthenium nanoparticles. Although not found to dissociate N<sub>2</sub>, Ru instead facilitates the formation of anion vacancies at the Ru–support interface. This demonstrates a new route for anion-vacancy<i>-</i>mediated heterogeneous catalysis.</p><p></p>

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Anion vacancies activate N2 to ammonia on Ba–Si orthosilicate oxynitride-hydride

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年2月17日

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  • Zhujun Zhang,
  • Kazuki Miyashita,
  • Tong Wu,
  • Jun Kujirai,
  • Kiya Ogasawara,
  • Jiang Li,
  • Yihao Jiang,
  • Masayoshi Miyazaki,
  • Satoru Matsuishi,
  • Masato Sasase,
  • Tomofumi Tada,
  • Hideo Hosono,
  • Masaaki Kitano

摘要

Anion vacancies on metal oxide surfaces have been studied as either active sites or promoting sites in various chemical reactions involving oxidation/reduction processes. However, oxide materials rarely work effectively as catalysts in the absence of transition metal sites. Here we report a Ba–Si orthosilicate oxynitride–hydride as a transition-metal-free catalyst for efficient ammonia synthesis via an anion-vacancy-mediated mechanism. The facile desorption of H− and N3− anions plus the flexibility of the crystal structure can accommodate a high density of electrons at vacancy sites, where N2 can be captured and directly activated to ammonia through hydrogenation processes. The ammonia synthesis rates reach 40.1 mmol g−1 h−1 at 300 °C by loading ruthenium nanoparticles. Although not found to dissociate N2, Ru instead facilitates the formation of anion vacancies at the Ru–support interface. This demonstrates a new route for anion-vacancy-mediated heterogeneous catalysis.