Wang Gaoxue, Batista Enrique R, Yang Ping
Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, United States.
Front Chem. 2023 Jan 5;10:1051496. doi: 10.3389/fchem.2022.1051496. eCollection 2022.
Ammonia (NH) is one of the basic chemicals in artificial fertilizers and a promising carbon-free energy storage carrier. Its industrial synthesis is typically realized the Haber-Bosch process using traditional iron-based catalysts. Developing advanced catalysts that can reduce the N activation barrier and make NH synthesis more efficient is a long-term goal in the field. Most heterogeneous catalysts for N-to-NH conversion are multicomponent systems with singly dispersed metal clusters on supporting materials to activate N and H molecules. Herein, we report single-component heterogeneous catalysts based on 5 actinide dioxide surfaces (ThO and UO) with oxygen vacancies for N-to-NH conversion. The reaction cycle we propose is enabled by a dual-site mechanism, where N and H can be activated at different vacancy sites on the same surface; NH is subsequently formed by H migration on the surface associative pathways. Oxygen vacancies recover to their initial states after the release of two molecules of NH, making it possible for the catalytic cycle to continue. Our work demonstrates the catalytic activities of oxygen vacancies on 5 actinide dioxide surfaces for N activation, which may inspire the search for highly efficient, single-component catalysts that are easy to synthesize and control for NH conversion.
氨（NH₃）是人工肥料中的基本化学品之一，也是一种很有前景的无碳储能载体。其工业合成通常通过使用传统铁基催化剂的哈伯-博施法来实现。开发能够降低氮活化能垒并使氨合成更高效的先进催化剂是该领域的一个长期目标。大多数用于氮转化为氨的多相催化剂是多组分体系，其中单分散的金属簇位于载体材料上以活化氮和氢分子。在此，我们报道了基于5种二氧化锕系元素表面（ThO₂和UO₂）且具有氧空位的单组分多相催化剂用于氮转化为氨。我们提出的反应循环是由双位点机制实现的，其中氮和氢可以在同一表面的不同空位处被活化；随后氨通过表面上的氢迁移以缔合途径形成。在释放两分子氨后，氧空位恢复到其初始状态，从而使催化循环能够继续。我们的工作展示了5种二氧化锕系元素表面上的氧空位对氮活化的催化活性，这可能会激发人们寻找易于合成和控制的用于氨转化的高效单组分催化剂。
