Lewis acid sites and flexible active centers synergistically boost efficient electrochemical ammonia synthesis

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 44; pp. 3476 - 3485
• Main Authors: Chen, Li-Bo, Wang, Tong-Hui, Lang, Xing-You, Jiang, Qing
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 12.11.2024
• Subjects: Acids; Adsorption; Ammonia; Boron; Boron nitride; Catalysts; Chemical reduction; Chemical synthesis; Density functional theory; Electrochemistry; Hydrogenation; Intermediates; Lewis acid; Nanotechnology; Nanotubes; Nitrogen; Tetrahedra; Transition metals
• DOI: 10.1039/d4ta04884a
• ISSN: 2050-7488

Much effort has been made to develop efficient electrochemical catalysts for the nitrogen reduction reaction (NRR). However, the activity and selectivity of present catalysts are still limited in their applications. Herein, from the perspective of Lewis acid-base interactions and flexible active centers, positively charged tetrahedron transition metal (TM) clusters were anchored onto boron nitride nanotubes (BNNTs) with B-vacancies to design a series of efficient NRR catalysts, meeting the above requirements. Through Density Functional Theory (DFT) calculations, our results uncover that the Mn 4 /BNNT (6, 6) system exhibits optimal activity characterized by a low limiting potential of only −0.29 V and high selectivity, as confirmed by the adsorption energy difference between nitrogen molecules and hydrogen proton (−0.73 eV). Owing to the existence of electron-deficient Lewis acid sites, the adsorption and activation of N 2 are strongly enhanced. Simultaneously, the flexible active center destabilizes the N-containing intermediates and upgrades the hydrogenation reaction process, facilitating the desorption of NH 3 or its further hydrogenation to NH 4 + . This innovative approach, employing a Lewis acid pair and a flexible active center to design efficient NRR catalysts, holds great promise for NH 3 synthesis under ambient conditions. The Lewis acid sites enhance N 2 adsorption and activation, while the flexible active center facilitates hydrogenation and NH 4 + formation, regenerating the catalyst.