Complementary Design in Multicomponent Electrocatalysts for Electrochemical Nitrogen Reduction: Beyond the Leverage in Activity and Selectivity

Tuning Coordination Structures of Zn Sites Through Symmetry-Breaking Accelerates Electrocatalysis

Manipulating the coordination environment of individual active sites in a precise manner remains an important challenge in electrocatalytic reactions. Herein, inspired by theoretical predictions, a facile procedure to synthesize a series of symmetry-breaking zinc metal-organic framework (Zn-MOF) catalysts with well-defined structures is presented. Benefiting from the optimized coordination microenvironment regulated by symmetry-breaking, Zn-N2 S2 -MOF exhibits the best performance of nitrogen (N2 ) reduction reaction (NRR) with NH3 yield rate of 25.07 ± 1.57 µg h-1  cm-2 and Faradaic efficiency of 44.57 ± 2.79% compared with reported Zn-based NRR catalysts. X-ray absorption near-edge structure shows that the symmetry-breaking distorts the coordination environment and modulates the delocalized electrons around the Zn sites, which favors the formation of unpaired low-valence Znδ+ , thereby facilitating the adsorption/activation of N2 . Theoretical calculations elucidate that low-valence Znδ+ in Zn-N2 S2 -MOF can effectively lower the energy barrier of potential determining step, promoting the kinetics and boosting the NRR activity. This work highlights the relationship between the precise coordination environment of metal sites and the catalytic activity, which offers insightful guidance for rationally designing high-efficiency electrocatalysts.

Metal-Based Electrocatalysts for Selective Electrochemical Nitrogen Reduction to Ammonia

Ammonia (NH3) plays a significant role in the manufacture of fertilizers, nitrogen-containing chemical production, and hydrogen storage. The electrochemical nitrogen reduction reaction (e-NRR) is an attractive prospect for achieving clean and sustainable NH3 production, under mild conditions driven by renewable energy. The sluggish cleavage of N≡N bonds and poor selectivity of e-NRR are the primary challenges for e-NRR, over the competitive hydrogen evolution reaction (HER). The rational design of e-NRR electrocatalysts is of vital significance and should be based on a thorough understanding of the structure-activity relationship and mechanism. Among the various explored e-NRR catalysts, metal-based electrocatalysts have drawn increasing attention due to their remarkable performances. This review highlighted the recent progress and developments in metal-based electrocatalysts for e-NRR. Different kinds of metal-based electrocatalysts used in NH3 synthesis (including noble-metal-based catalysts, non-noble-metal-based catalysts, and metal compound catalysts) were introduced. The theoretical screening and the experimental practice of rational metal-based electrocatalyst design with different strategies were systematically summarized. Additionally, the structure-function relationship to improve the NH3 yield was evaluated. Finally, current challenges and perspectives of this burgeoning area were provided. The objective of this review is to provide a comprehensive understanding of metal-based e-NRR electrocatalysts with a focus on enhancing their efficiency in the future.

Role of Peripheral Coordination Boron in Electrocatalytic Nitrogen Reduction over N-Doped Graphene-Supported Single-Atom Catalysts

In this work, we investigate the effect of peripheral B doping on the electrocatalytic nitrogen reduction reaction (NRR) performance of N-doped graphene-supported single-metal atoms using density functional theory (DFT) calculations. Our results showed that the peripheral coordination of B atoms could improve the stability of the single-atom catalysts (SACs) and weaken the binding of nitrogen to the central atom. Interestingly, it was found that there was a linear correlation between the change in the magnetic moment (μ) of single-metal atoms and the change in the limiting potential (U_L) of the optimum NRR pathway before and after B doping. It was also found that the introduction of the B atom suppressed the hydrogen evolution reaction, thereby enhancing the NRR selectivity of the SACs. This work provides useful insights into the design of efficient SACs for electrocatalytic NRR.