Electronic Structure Based Intuitive Design Principle of Single‐Atom Catalysts for Efficient Electrolytic Nitrogen Reduction

Abstract

As an alternative to cost‐ and energy intensive Haber‐Bosch process, the implementation of electrolytic ammonia synthesis from dinitrogen molecule has been a long‐sought goal. State‐of‐the‐art electrocatalysts for nitrogen reduction reaction (NRR) face not only activity but also selectivity problem with the competitive hydrogen evolution reaction (HER). Recently, single‐atom catalysts (SACs) have emerged as promising for various reactions as they combine the best of homogenous and heterogenous catalysts. The reason for their high activity compared to their bulk and nanoparticle counterparts are yet to be completely understood. Inspired by the structure of nitrogenase FeMo cofactor, here we studied 13 transition metals anchored on MoS2 monolayer at Mo‐top positions, as possible electrolytic NRR catalysts using first‐principles methods. Employing the implicit solvation model, we calculated free energy barriers for proton abstraction by N2 molecule in end‐on configuration and adsorption free energy of hydrogen on all SACs. Based on these two parameters, Fe, Co, and Ru were found to be the most active and highly selective electrolytic NRR catalysts. Compared with other mechanisms, the limiting potentials (and hence activity) for enzymatic mechanism were found to be higher on these three SACs, with Ru SAC having a very low overpotential of 0.38 V vs SHE. Bader charge transferred from transition metal to N2 molecule and group number of transition metals correlate strongly with the NRR activity and hence emerge as two key descriptors for catalytic activity. These intuitive principles for rational designing of promising alternatives to the currently used bulk Ru(0001) catalyst could accelerate the search for highly efficient and selective SACs for electrolytic NRR.

Rational Design of Single-Atom Catalysts for Enhanced Electrocatalytic Nitrogen Reduction Reaction

“…The electrons are donated from the TMs to the NN antibonding orbital, subsequently reducing the NN bond strength. Furthermore, the electrons from the nitrogen molecule is back-donated to the empty d-orbitals of the TMs. ,, This back-donation is enhanced synergistically. The charge density difference plot in Figure S3a,b shows the donation of the electron from the metal surface and back-donation from N 2 .…”

“…Their properties differ significantly from those of the nanoclusters and nanoparticles due to the presence of discrete states, providing extraordinary selectivity, activity, and stability to the catalyst. , Several studies have already been performed on single-atom catalysts for CO 2 reduction reaction (CO2RR), − CO oxidation reaction (COOR), , hydrogen evolution reaction (HER), − and oxygen evolution reaction (OER) . Few computational studies and experimental studies have also been conducted on nitrogen reduction reaction involving various two-dimensional materials as supports. − However, the overall efficiencies of such catalysts are unsatisfactory in terms of activity and selectivity, thereby limiting their large-scale industrial applications. Therefore, there is a need to explore new catalysts with sufficiently high activity and selectivity and establish theoretical design principles to guide the discovery of promising SACs.…”

Chemical hardness-driven interpretable machine learning approach for rapid search of photocatalysts

“…Hence, these 2DO materials are also expected to have efficient photocatalytic activities. In addition, our HT scheme can also help in the identification of photocatalysts suitable for other reactions such as carbon dioxide reduction reaction (CO 2 RR) 80 , nitrogen reduction reaction (NRR) 81 , and pollutant degradation 2 , which require further investigations. There is also a possibility for the 2DO materials belonging to the Hm (e.g., Ni(OH) 2 82 ) and Mh (e.g., Co(OH) 2 83 ) classes to act as potential candidates for photo(electro)catalysis.…”

Photo-assisted high performance single atom electrocatalysis of the N2 reduction reaction by a Mo-embedded covalent organic framework

“…This difference can be attributed to the higher amount of back-donation taking place in the sideon the than the end-on mode. 42 The charge redistribution can be visualized by the charge accumulation and depletion displayed by the orange and green region in Fig. 2(a) and (b), where the electron transfer in the side-on case is more obvious than the end-on case.…”