Riyaz Mohd, Goel Neetu
Theoretical & Computational Chemistry group Department of Chemistry & Centre for Advanced studies in Chemistry, Panjab University, Chandigarh-, 160014, India.
Chemphyschem. 2019 Aug 5;20(15):1954-1959. doi: 10.1002/cphc.201900519. Epub 2019 Jun 21.
Reduction of dinitrogen to ammonia under ambient conditions is a long-standing challenge. The few metal-based catalysts proposed have conspicuous disadvantages such as high cost, high energy consumption, and being hazardous to the environment. Single-atom catalysis has emerged as a new frontier in heterogeneous catalysis and metal atoms atomically dispersed on supports receive more and more attention owing to rapid advances in synthetic methodologies and computational modeling. Herein, we propose metal atoms embedded in divacant graphene as a catalyst for N fixation based on density functional calculations. We systematically investigate the potential of using transition metal like Cr, Mn, Fe, Mo and Ru as catalysts and our study reveals that Cr embedded in graphene exhibit good catalytic activity for N fixation. The synergy between the metal atoms and graphene surface provides a stable support to the metal center that has a high spin density to promote adsorption of N and activation of its N≡N triple bond. Our study deciphers the mechanism of conversion of N to ammonia following two possible reaction pathways, distal and enzymatic routes, via sequential protonation and reduction of activated N . The study provides a rational framework for conversion of dinitrogen to ammonia using single atom catalyst.
在环境条件下将二氮还原为氨是一个长期存在的挑战。所提出的少数金属基催化剂存在明显的缺点，如成本高、能耗高以及对环境有害。单原子催化已成为多相催化的一个新前沿领域，由于合成方法和计算建模的快速发展，原子分散在载体上的金属原子受到越来越多的关注。在此，我们基于密度泛函计算提出嵌入双空位石墨烯中的金属原子作为固氮催化剂。我们系统地研究了使用铬、锰、铁、钼和钌等过渡金属作为催化剂的潜力，我们的研究表明，嵌入石墨烯中的铬对固氮表现出良好的催化活性。金属原子与石墨烯表面之间的协同作用为具有高自旋密度的金属中心提供了稳定的支撑，以促进氮的吸附及其N≡N三键的活化。我们的研究通过活化氮的顺序质子化和还原，揭示了氮通过两种可能的反应途径（远端途径和酶促途径）转化为氨的机制。该研究为使用单原子催化剂将二氮转化为氨提供了一个合理的框架。
