Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
J Phys Chem B. 2014 Jan 9;118(1):195-203. doi: 10.1021/jp406535p. Epub 2013 Dec 20.
Recently a novel approach to the photocatalytic reduction of molecular nitrogen under ambient conditions was reported in which hydrated electrons generated from ultraviolet illumination of diamond served as the reducing agent [Zhu, D.; Zhang, L.; Ruther, R. E.; Hamers, R. J. Photo-Illuminated Diamond as a Solid-State Source of Solvated Electrons in Water for Nitrogen Reduction. Nat. Mater. 2013, 12, 836-841]. This surprising reduction of N2 by aqueous solvated electrons is absent from the vast existing radiolysis literature and thus has little mechanistic precedent. In this work, a combination of experimental and computational approaches is used to elucidate the detailed molecular-level mechanistic pathway from nitrogen to ammonia. A variety of approaches, including electronic structure calculations, molecular dynamics simulations, kinetic modeling, and pH-dependent experimental measures of NH3 and competing H2 production, implicate a hydrogen atom addition mechanism at early reduction steps and sequential protonation/direct reduction by a solvated electron at later steps, thus involving both direct and indirect reactions with solvated electrons. This work provides a framework for understanding the possible application of solvated electrons as energetic reducing agents for chemically inert species under mild conditions.
最近，有人报道了一种在环境条件下光催化还原氮气的新方法，其中金刚石在紫外光照射下产生的水合电子作为还原剂[Zhu, D.; Zhang, L.; Ruther, R. E.; Hamers, R. J. Photo-Illuminated Diamond as a Solid-State Source of Solvated Electrons in Water for Nitrogen Reduction. Nat. Mater. 2013, 12, 836-841]。这种由水合电子还原氮气的惊人反应在现有的辐解文献中是不存在的，因此几乎没有任何机制先例。在这项工作中，采用实验和计算相结合的方法阐明了从氮气到氨的详细分子水平的反应机制。各种方法，包括电子结构计算、分子动力学模拟、动力学建模和 pH 值依赖性的氨和竞争氢生成的实验测量，表明在早期还原步骤中存在氢原子加成机制，而在后期步骤中通过水合电子进行连续质子化/直接还原，因此涉及到与水合电子的直接和间接反应。这项工作为理解在温和条件下水合电子作为化学惰性物质的高能还原剂的可能应用提供了一个框架。
