Rationally designed bimetallic iron cobalt boride for electrocatalytic N 2 reduction to ammonia Vineet Mishra and G. Ranga Rao Indian Institute of Technology Madras, India Electrocatalytic nitrogen reduction reaction (eNRR) at ambient conditions is an environment-friendly and sustainable pathway for ammonia production. However, the low ammonia yield and poor faradaic efficiency, attributed to the difficulty in N 2 adsorption, N≡N bond activation and competing hydrogen evolution reaction (HER) in aqueous electrolyte medium, inhibit its practical applications. 1 Hence, development of robust and efficient electrocatalyst is highly desirable. In this work, designing N 2 reduction catalyst is purely based on assembling two types of metals in the form of a boride. First, a metal having low dissociation energy barrier and another metal with high dissociation energy barrier for N 2 to achieve optimised coverage of dissociated nitrogen atoms on the catalyst surface during electrocatalytic ammonia synthesis. 2 Apart from this, N 2 being Lewis base can preferentially be adsorbed on the Lewis acid boron over H + in acidic medium which further suppresses HER. 3,4 Hence, keeping all the above facts in mind, we have rationally designed a bimetallic iron cobalt boride (FeCoB) using high energy ball-milling method followed by high temperature annealing. The electrocatalytic N 2 reduction was performed in a two compartment H-cell separated by 211 nafion membrane using 0.05 M H 2 SO 4 aqueous electrolyte. After the electrocatalytic N 2 reduction, the resultant NH 4 + ion concentration in the electrolyte was quantitatively analysed with the help of indophenol-blue method. Absorbance of the solution was measured using UV-Visible spectrophotometer at a λ max of 655 nm. As synthesised FeCoB shows higher yield of NH 4 + than the corresponding monometallic FeB and CoB electrocatalysts. References 1. G. Qing, R. Ghazfar, S. T. Jackowski, F. Habibzadeh, M. M. Ashtiani, C-P Chen, M. R. Smith III, T. W. Hamann, Chem. Rev ., 2020, 120 , 5437-5516. 2. C. J. H. Jacobsen, S. Dahl, B. S. Clausen, S. Bahn, A. Logadottir, J. K. Norskov, J. Am. Chem. Soc. , 2001, 123 , 8404-8405. 3. C. Liu, Q. Li, C. Wu, J. Zhang, Y. Jin, D. R. MacFarlane, C. Sun, J. Am. Chem. Soc ., 2019, 141 , 2884-2888. 4. A. Biswas, S. Kapse, B. Ghosh, R. Thapa, R.S. Dey, PNAS, 2022, 119 , No. 33, e2204638119.
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