Electrocatalytic Nitrogen Reduction Reaction Activity Research Articles

Enhanced ammonia yield rate from nitrogen on collapsed dodecahedral-shaped Co/NC electrocatalyst

Nowadays, multi-component non-precious metal catalysts have been considered as a significant strategy for enhancing the yield of synthesizing NH3 by electrocatalytic nitrogen reduction reaction (E-NRR). In the present work, carbon composites doped with well-dispersed Co and N (Co/NC) were prepared by pyrolyzing zeolitic imidazolate framework-67 (ZIF-67) at various temperatures protected under a N2 flow. Co/NC exhibits a collapsed dodecahedral morphology with a mesoporous structure (3.5-4 nm). The chemical states of Co/N and the structural defects of C are closely related to the carbonization temperature. In a N2-saturated 0.1 M KOH electrolyte, the as-prepared catalysts exhibit an NH3 yield rate (Y(NH3)) of 60.57 μg h-1 mgcat.-1 and a Faradaic efficiency (FE) of 23.3% at -0.1 V (vs the reversible hydrogen electrode, RHE) at ambient conditions. The enhanced E-NRR activity of Co/NC may primarily originate from an associative distal pathway on the Co-N3-C sites and the carbon defects in an alkaline electrolyte. Specifically, this work presents a three-component E-NRR catalyst with excellent stability and great activity based on Co/NC.

Repairable body-centered cubic Fe0 anchoring on porous hollow nitrogen-doped carbon spheres with adjusting electron distribution for efficient electrocatalytic ammonia synthesis

Electrocatalytic nitrogen reduction reaction (ENRR) is a promising and efficient method for ammonia production. However, ENRR is restricted by the adsorption and activation of N2. Herein, an efficient nitrogen reduction reaction (NRR) electrocatalyst loaded with zero valent iron (ZVI) particles onto porous nitrogen-doped carbon (NC) hollow spheres is reported. The optimal Fe@10N3C-950 exhibits excellent performance with high ammonia (NH3) yield (152.28 µg h−1 mgcat−1) and Faradaic efficiency (FE, 54.55 %) at − 0.3 V (versus reversible hydrogen electrode, vs. RHE). Bader charge shows that the adsorbed N2 acquires more electrons from Fe sites with body-centered cubic (BCC) structure to better activate N2. Moreover, i-t experiments are performed before electrocatalytic NH3 production to effectively eliminate the effect of oxidation on ZVI and thus, maintain high ENRR activity for Fe@10N3C-950. Theoretical calculations indicate that nitrogen doping not only reduces the Gibbs free energy of rate determining step (RDS), but the BCC-structured Fe can also decrease the energy barriers of N2 activation and RDS.

Key Role of Local Chemistry in Lattice Nitrogen‐Participated N2‐to‐NH3 Electrocatalytic Cycle over Nitrides

AbstractMetal nitrides offer great opportunities for improving activity and selectivity of electrocatalytic nitrogen reduction reaction (ENRR) via the lattice nitrogen‐participated mechanism. Understanding the role of local chemistry of lattice nitrogen is important for establishing rational design principles of nitride catalysts. Herein, high‐throughput theoretical calculations are employed to investigate lattice nitrogen‐participated ENRR over a family of antiperovskite nitrides (M′M3N, M and M′ are different metal atoms) with highly tunable surrounding environments of N atoms. The M′M3N structure comprises isolated N atoms in the center, M atoms in the first coordination shells, and M′ atoms in the second coordination shells. An appropriate M‐N bond strength is found to be crucial for designing ideal nitride catalysts. Specifically, weak M‐N bonding facilitates the participation of lattice nitrogen and better activity, but too weak M‐N bonding results in structural instability of antiperovskite. The type of M element governs M‐N bond strength through adjusting hybridization interactions between M orbital and N orbital, and the M′ element can further finely regulate M‐N bond strength via M‐M′ polarization effects. Finally, AgBa3N, AlBa3N, GaBa3N catalysts are screened to possess greater ENRR activity than the benchmarking Ru (0001) catalysts and high selectivity toward hydrogen evolution reaction.

P‐d Orbital Hybridization Engineered Single‐Atom Catalyst for Electrocatalytic Ammonia Synthesis

The rational design of metal single‐atom catalysts (SACs) for electrochemical nitrogen reduction reaction (NRR) is challenging. Two‐dimensional metal–organic frameworks (2DMOFs) is a unique class of promising SACs. Up to now, the roles of individual metals, coordination atoms, and their synergy effect on the electroanalytic performance remain unclear. Therefore, in this work, a series of 2DMOFs with different metals and coordinating atoms are systematically investigated as electrocatalysts for ammonia synthesis using density functional theory calculations. For a specific metal, a proper metal‐intermediate atoms p‐d orbital hybridization interaction strength is found to be a key indicator for their NRR catalytic activities. The hybridization interaction strength can be quantitatively described with the p−/d‐ band center energy difference (∆d‐p), which is found to be a sufficient descriptor for both the p‐d hybridization strength and the NRR performance. The maximum free energy change (ΔGmax) and ∆d‐p have a volcanic relationship with OsC4(Se)4 located at the apex of the volcanic curve, showing the best NRR performance. The asymmetrical coordination environment could regulate the band structure subtly in terms of band overlap and positions. This work may shed new light on the application of orbital engineering in electrocatalytic NRR activity and especially promotes the rational design for SACs.

Composition-dependent electrochemical activity of Ag-based alloy nanotubes for efficient nitrogen reduction under ambient conditions

The composition-activity relationship is highly desirable for electrocatalytic nitrogen reduction reaction (NRR) because it could guide the rational design of efficient NRR catalysts. In this work, the composition effect of Ag-based alloy nanotubes on electrocatalytic NRR activity is systematically investigated. It is found that, among AgAu nanotubes with atomic ratio from 8:1 to 1:2, Ag2Au1 alloy nanotubes achieve the largest enhancement for NRR catalytic activity. Specifically, the NH3 production rate and faradaic efficiency of Ag2Au1 nanotubes are 21.7 μg h−1 mgcat−1 and 3.8% at −0.30 V vs. RHE, respectively, which were 3.0 and 3.6 times higher than those of Ag nanowires. Compared with Ag2Pd1 and Ag2Pt1 nanotubes, Ag2Au1 hollow nanotubes also exhibit a better NRR catalytic activity. Theoretical calculation results indicate that the negative ion characteristic of Au atoms in the Ag2Au1 alloy is favorable for the adsorption and activation of N2. Moreover, Ag2Au1 nanotubes showed stable NH3 yield rate and faradaic efficiency up to 18 h, revealing its great potential for promising NRR electrocatalysis.

The Role of Oxidation of Silver in Bimetallic Gold-Silver Nanocages on Electrocatalytic Activity of Nitrogen Reduction Reaction.

Electrochemical ammonia synthesis from nitrogen and water provides an alternative route to the thermochemical process (Haber-Bosch) in a clean, sustainable, and decentralized way if electricity is generated from renewable sources. We have previously demonstrated the use of bimetallic hollow Au-Ag nanocages as an effective electrocatalyst for electrosynthesis of ammonia in an aqueous solution. The stability of the electrocatalyst during electrochemical nitrogen reduction reaction (NRR) is of paramount importance when considering the feasibility of electrochemical NRR for industrial applications. Here, the role of oxidation of silver in bimetallic Au-Ag nanocages with various localized surface plasmon resonance (LSPR) peak positions on electrocatalytic activity of NRR is studied by oxygen treatment of Ag through the simple oxidation process to form Ag2O-Au nanocages. Electrocatalytic NRR activity with an NH3 yield rate of 2.14 µg cm-2 h-1 and Faradaic efficiency of 23.4% has been achieved at -0.4V vs. RHE using Ag2O-Au-719. This electrochemical performance is a substantial reduction to our previously reported NRR activity using Ag-Au-715 nanocages (3.74 µg cm-2 h-1 and 35.9% at -0.4V vs. RHE). This work highlights the importance of an O2-free environment in electrochemical NRR for the stable N2 electrolysis operation and discerns the role of Ag on the selectivity and activity of bimetallic Au-Ag nanocages toward NRR.

The Role of Oxidation of Silver in Bimetallic Gold–Silver Nanocages on Electrocatalytic Activity of Nitrogen Reduction Reaction

Electrochemical ammonia synthesis from nitrogen and water provides an alternative route to the thermochemical process (Haber-Bosch) in a clean, sustainable, and decentralized way if electricity is generated from renewable sources. We previously demonstrated the use of bimetallic hollow Au–Ag nanocages as an effective electrocatalyst for electrosynthesis of ammonia in an aqueous solution. The stability of the electrocatalyst during electrochemical nitrogen reduction reaction (NRR) is of paramount importance when considering the feasibility of electrochemical NRR for industrial applications. Here, the role of oxidation of silver in bimetallic Au–Ag nanocages with various localized surface plasmon resonance peak positions on electrocatalytic activity of NRR is studied by oxygen treatment of Ag through the simple oxidation process to form Ag2O–Au nanocages. Electrocatalytic NRR activity with an NH3 yield rate of 2.14 μg cm–2 h–1 and Faradaic efficiency of 23.4% was achieved at −0.4 V versus reversible hydroge...