Progress of Experimental and Computational Catalyst Design for Electrochemical Nitrogen Fixation

Abstract

Large-scale ammonia synthesis via the electrochemical nitrogen reduction reaction (eNRR) under mild reaction conditions represents a green prospect for agriculture, industry, and energy. This bioinspired and carbon-free reaction has been proposed as an ideal alternative to the Haber–Bosch process. However, the yield and selectivity of the current eNRR have not met the requirements for industrialization. Mechanistic understanding and catalysts’ design are still long-term pursuits in this field, where theoretical simulations will have significant contributions. In this Review, we will start with the natural N2 fixation enzymes, the nitrogenases, followed by a summary of the key experimental eNRR performances on hundreds of recently reported catalysts, and we analyze the general trend and challenges before eNRR can significantly impact the ammonia industry. Then, we will systematically review the recent progress and contributions of computational studies in understanding the reaction mechanism and rational catalyst design for eNRR. The fundamental principles, reaction mechanisms, crucial theoretical criteria, modeling methods, and computationally predicted catalysts for eNRR are systematically summarized and discussed. Finally, we outline the current challenges and future opportunities for experimental and computational studies of electrochemical N2 reduction.

Catalysis of dinitrogen activation and reduction by a single Fe13 cluster and its doped systems

“…According to the “acceptance-donation” mechanism, the N 2 molecule functions as σ donor toward the empty d-orbitals of the transition metal; meanwhile, the electrons would transfer from the occupied d-orbitals of the metal to the anti-bonding orbitals of the N 2 molecule, thus weakening the NN bond (π back-donation). 77 Here, the Bader charge analysis showed that the values of charge population on the Nb atom of Fe 12 Nb were significantly more negative than those of the other shell-doped clusters, which would facilitate π back-donation (Fig. S6, ESI†); this is indicative of its high activity in N 2 activation.…”

Enhanced Catalytic Activity of Bimetallic Ordered Catalysts for Nitrogen Reduction Reaction by Perturbation of Scaling Relations

“…However, the performance of electrocatalytic NRR is limited by the low reaction reactivity and selectivity because of the large limiting potential needed to activate the inert nitrogen and the seriously competitive HER, respectively, which advances the screening and development of new catalysts. Numerous studies have assessed the efficiency of different catalysts toward NRR, including monometallic catalysts, single-atom catalysts, nanoclusters, and transition-metal compounds (e.g., nitrides, carbides, oxides, and borides). ,− Notably, alloys are some of the important candidates for exploring high-efficiency catalysts due to the synergistic effect between different metal atoms that can simultaneously regulate the reaction activity and selectivity. − It was previously found that bimetallic alloys can be used as efficient NRR catalysts. − For instance, nanoporous CuMn and AuCu nanocatalysts have been synthesized and exhibit high ammonia yield rates with low applied voltages. It is worth noting that bimetallic alloys are also effective electrode catalysts in other fields like the oxygen evolution reaction (OER) , and the CO 2 reduction reaction. , …”

Creating Highly Active Iron Sites in Electrochemical N2 Reduction by Fabricating Strongly‐Coupled Interfaces

“…[ 1 ] The current ammonia synthesis in the industry is mainly based on the Haber‐Bosch process, which is racked by harsh operating conditions and voracious energy requirements. [ 2 ] Electrocatalytic N 2 reduction reaction (NRR) is a newly emerging route to produce ammonia in the past decades with distinctive advantages including a moderate reaction environment and relatively high catalytic efficiency in theory. [ 3 ] Despite great progress made, the reaction still suffers from the sluggish kinetics induced by the inert N≡N bonds and competing hydrogen evolution reaction, leaving pressing challenges in catalyst design and surface state regulation.…”