Molybdenum bound nitrogen‐doped graphene catalyst for reduction of N₂ to NH₃ and NH₂NH₂, using FLP as a co‐catalyst: A DFT study

Abstract

Chemists have long been pursuing the aim of synthesising practically viable low temperature catalysts with high stability, activity and selectivity towards the generation of ammonia under less expensive reaction conditions by using H 2 and N 2 . In this regard, we have used molybdenum bound nitrogen-doped graphene as a catalyst in the present computational investigation. We developed a new concept of the Frustrated Lewis Pair [AH] + [BH] À (FLP-H 2 ), which can be used as a source of hydrogen to functionalise the coordinated dinitrogen into ammonia. Furthermore, the utilisation of FLP-H 2 can prevent the competition in binding of N 2 and H 2 with Mo centre and enable the product formation. Our computed thermodynamic and kinetic barriers clearly reveal that the molybdenum bound nitrogen-doped graphene can be used as a catalyst to activate and functionalise the dinitrogen. In the proposed catalytic cycle, H + and H À can be added in an alternate manner using the FLP-H 2 source to yield NH 3 and NH 2 NH 2 . Some thermodynamically viable penta-coordinated [M] H intermediates have also been identified in the current study. K E Y W O R D SDFT (density functional theory), dinitrogen, FLP (frustrated Lewis pair), molybdenum, nitrogen-doped graphene | INTRODUCTIONChemists are still grappling with the formation of ammonia at low temperature and pressure of 1 atm. Dinitrogen is difficult to activate because of its inert nature. [1][2][3][4][5][6][7][8][9][10][11][12][13] Several investigations have been conducted in recent years to develop a suitable catalyst for the activation and functionalization of dinitrogen. Every year, more than 100 million tonnes of ammonia are used in a variety of applications. The Haber-Bosch process for producing ammonia is commonly utilised, and it involves extreme experimental conditions such as high temperature and high pressure. [14][15][16] On the other hand, the biological conversion of atmospheric dinitrogen to ammonia occurs due to the activity of nitrogenase enzyme at ambient reaction conditions. [17][18][19][20][21][22][23] This study is dedicated to Prof. Dr. Gajapathy Dasaratharam, Muthurangam Government Arts College, Vellore, TN, India, on the occasion of his 75th birthday celebration.