Efficient N2 Reduction Reaction Research Articles

Mesoporous Au3Pd Film on Ni Foam: A Self-Supported Electrocatalyst for Efficient Synthesis of Ammonia.

As a promising alternative approach to industrial N2 fixation process, electrocatalytic N2 reduction reaction (NRR) can achieve efficient, sustainable, and eco-friendly ammonia production under ambient conditions. Developing efficient NRR catalysts is critical for the electrochemical ammonia synthesis. Herein, self-supported mesoporous Au3Pd film on Ni foam (mAu3Pd/NF) has been in situ synthesized via a micelle-assisted replacement strategy. Combination of bimetallic compositions, interconnected mesoporous structure, and binder-free characteristic, the mAu3Pd/NF shows a superior NRR performance in 0.1 M Na2SO4. This micelle-assisted replacement route is very important to construct efficient self-supporting mesoporous films for the NRR and other fields.

Boosted Electrocatalytic N2 Reduction on Fluorine-Doped SnO2 Mesoporous Nanosheets.

The development of highly active and durable electrocatalysts toward the N2 reduction reaction (NRR) holds a key to ambient electrocatalytic NH3 synthesis. Herein, fluorine (F)-doped SnO2 mesoporous nanosheets on carbon cloth (F-SnO2/CC) were developed as an efficient NRR electrocatalyst. Benefiting from the combined structural advantages of mesoporous nanosheet structure and F-doping, the F-SnO2/CC exhibited high NRR activity with an NH3 yield of 19.3 μg h-1 mg-1 and a Faradaic efficiency of 8.6% at -0.45 V (vs RHE) in 0.1 M Na2SO4, comparable or even superior to those of most reported NRR electrocatalysts. Density functional theory calculations revealed that the F-doping could readily tailor the electronic structure of SnO2 to render it with improved conductivity and increased positive charge on active Sn sites, leading to the lowered reaction energy barriers and boosted NRR activity.

Single and double boron atoms doped nanoporous C2N–h2D electrocatalysts for highly efficient N2 reduction reaction: a density functional theory study

The electrocatalytical process is the most efficient way to produce ammonia (NH3) under ambient conditions, but developing a highly efficient and low-cost metal-free electrocatalysts remains a major scientific challenge. Hence, single atom and double boron (B) atoms doped 2D graphene-like carbon nitride (C2N–h2D) electrocatalysts have been designed (B@C2N and B2@C2N), and the efficiency of N2 reduction reaction (NRR) is examined by density functional theory calculation. The results show that the single and double B atoms can both be strongly embedded in natural nanoporous C2N with superior catalytic activity for N2 activation. The reaction mechanisms of NRR on the B@C2N and B2@C2N are both following an enzymatic pathway, and B2@C2N is a more efficient electrocatalyst with extremely low overpotential of 0.19 eV comparing to B@C2N (0.29 eV). In the low energy region, the hydrogenation of N2 is thermodynamically more favorable than the hydrogen production, thereby improving the selectivity for NRR. Based on these results, a new double-atom strategy may help guiding the experimental synthesis of highly efficient NRR electrocatalysts.

Metal-free N, S co-doped graphene for efficient and durable nitrogen reduction reaction

Electrochemical conversion of N2–NH3 provides a green and sustainable alternative for artificial NH3 synthesis but requires effective electrocatalysts to promote N2 reduction reaction (NRR). This work reported the first application of N, S co-doped graphene (NSG) as an efficient metal-free NRR catalyst. It was found that the NSG exhibited a high NH3 yield of 7.7 μg h−1 mg−1 and Faradaic efficiency of 5.8% at − 0.6 V versus reversible hydrogen electrode under ambient conditions, which largely outperformed undoped and single-doped counterparts, and compared favorably to most reported metal-based NRR catalysts. The combination of density functional theory calculations and experiments revealed that the N, S co-doping could effectively improve the NRR of graphene by promoting the N2 adsorption and N≡N bond elongation, boosting the electron transfer and creating more defective/active sites. Furthermore, the NSG showed an excellent selectivity and stability, suggesting its great potential for efficient electrochemical synthesis of NH3.

Interfacial engineering of cobalt sulfide/graphene hybrids for highly efficient ammonia electrosynthesis

Electrocatalytic N2 reduction reaction (NRR) into ammonia (NH3), especially if driven by renewable energy, represents a potentially clean and sustainable strategy for replacing traditional Haber-Bosch process and dealing with climate change effect. However, electrocatalytic NRR process under ambient conditions often suffers from low Faradaic efficiency and high overpotential. Developing newly regulative methods for highly efficient NRR electrocatalysts is of great significance for NH3 synthesis. Here, we propose an interfacial engineering strategy for designing a class of strongly coupled hybrid materials as highly active electrocatalysts for catalytic N2 fixation. X-ray absorption near-edge spectroscopy (XANES) spectra confirm the successful construction of strong bridging bonds (Co-N/S-C) at the interface between CoS x nanoparticles and NS-G (nitrogen- and sulfur-doped reduced graphene). These bridging bonds can accelerate the reaction kinetics by acting as an electron transport channel, enabling electrocatalytic NRR at a low overpotential. As expected, CoS2/NS-G hybrids show superior NRR activity with a high NH3 Faradaic efficiency of 25.9% at -0.05 V versus reversible hydrogen electrode (RHE). Moreover, this strategy is general and can be extended to a series of other strongly coupled metal sulfide hybrids. This work provides an approach to design advanced materials for ammonia production.

Mn3O4 nanoparticles@reduced graphene oxide composite: An efficient electrocatalyst for artificial N2 fixation to NH3 at ambient conditions

Currently, industrial-scale NH3 production almost relies on energy-intensive Haber-Bosch process from atmospheric N2 with large amount of CO2 emission, while low-cost and high-efficient catalysts are demanded for the N2 reduction reaction (NRR). In this study, Mn3O4 nanoparticles@reduced graphene oxide (Mn3O4@rGO) composite is reported as an efficient NRR electrocatalyst with excellent selectivity for NH3 formation. In 0.1 M Na2SO4 solution, such catalyst obtains a NH3 yield of 17.4 μg·h−1·mg−1cat. and a Faradaic efficiency of 3.52% at −0.85 V vs. reversible hydrogen electrode. Notably, it also shows high electrochemical stability during electrolysis process. Density functional theory (DFT) calculations also demonstrate that the (112) planes of Mn3O4 possess superior NRR activity.

A perovskite La2Ti2O7 nanosheet as an efficient electrocatalyst for artificial N2 fixation to NH3 in acidic media.

The synthesis of NH3 heavily relies on the Haber-Bosch process suffering from a large amount of CO2 emission and energy consumption. Possessing eco-friendly and sustainable characteristics, electrochemical reduction is considered as a promising candidate for artificial N2 fixation under ambient conditions, but efficient electrocatalysts are crucial for the N2 reduction reaction (NRR). In this communication, we report that perovskite La2Ti2O7 nanosheets behave as an efficient NRR electrocatalyst with excellent selectivity under ambient conditions. In 0.1 M HCl, this catalyst achieves a high NH3 yield rate of 25.15 μg h-1 mgcat.-1 with a faradaic efficiency of 4.55% at -0.55 V vs. a reversible hydrogen electrode. Notably, it also shows high electrochemical stability.

Rational Design of Fe–N/C Hybrid for Enhanced Nitrogen Reduction Electrocatalysis under Ambient Conditions in Aqueous Solution

Developing efficient noble-metal-free catalysts for the electrochemical N2 reduction reaction (NRR) under ambient conditions shows promise in fertilizer production and hydrogen storage. Here, as a proof-of-concept prototype, we design and implement an Fe–N/C–carbon nanotube (CNT) catalyst derived from a metal–organic framework and carbon-nanotube-based composite with built-in Fe–N3 active sites. This catalyst exhibits enhanced NRR activity with NH3 production (34.83 μg·h–1·mg–1cat.), faradaic efficiency (9.28% at −0.2 V vs RHE), selectivity, and stability in 0.1 M KOH aqueous media under mild conditions. Experimental and theoretical results both reveal that Fe–N3 species are the primary catalytically active centers for the NRR. This work provides insight into precise construction of more efficient and stable NRR electrocatalysts and further expands the possibilities of transition metal–nitrogen–carbon (M–N–C)-based nanomaterials in NRR fields.

NbO2 Electrocatalyst Toward 32% Faradaic Efficiency for N2 Fixation

AbstractThe electrocatalytic N2 reduction reaction (NRR) to produce ammonia is an attractive but highly challenging approach, due to the extreme inertness of N2 molecules and significantly lower N2 concentration compared to the surrounding water molecules. Herein, NbO2 nanoparticles are demonstrated as an efficient NRR electrocatalyst with significantly improved electrochemical performances. Compared to Nb2O5 with a similar crystal structure unit but different linkage, the Nb4+ cation not only provides empty d‐orbitals for strong N2 adsorption, but also a single d‐electron to further enable back donation to activate the NN triple bond. As a result, the NbO2 nanoparticles present an outstanding ammonia production rate of 11.6 µg h−1 mgcat.−1 at −0.65 V versus reversible hydrogen electrode (RHE) and an excellent electrochemical stability, significantly higher than those of the Nb2O5 nanorods under similar conditions. More importantly, a peak faradaic efficiency of ammonia production of 32% is obtained for NbO2 at −0.60 V versus RHE, which is one of the highest reported NRR faradaic efficiencies to date.

High-Performance Electrohydrogenation of N2 to NH3 Catalyzed by Multishelled Hollow Cr2O3 Microspheres under Ambient Conditions

Electrohydrogenation of N2 to NH3 is emerging as an environmentally benign strategy to tackle the issues associated with the energy-intensive, CO2-emitting Haber–Bosch process. However, the method is severely challenged by N2 activation and needs efficient N2 reduction reaction (NRR) catalysts. Here, we report that multishelled hollow Cr2O3 microspheres (MHCMs), which are synthesized by a facile synthetic route, can serve as efficient and selective non-noble metal electrocatalysts for NRR. In 0.1 M Na2SO4 solution, the MHCMs achieve a high Faradaic efficiency (6.78%) and a large NH3 yield (25.3 μg h–1 mgcat–1) at −0.9 V vs reversible hydrogen electrode. The MHCMs also exhibit high stability during the reaction. Density functional theory calculations suggest that NRR over MHCMs occurs via both distal associative and partially alternative routes.

Efficient and durable N2 reduction electrocatalysis under ambient conditions: β-FeOOH nanorods as a non-noble-metal catalyst.

NH3 is one of the most important chemicals with a wide range of applications. NH3 is mainly produced via the Haber-Bosch process, which leads to large energy consumption and carbon emission. Electrochemical reduction has emerged as an environmentally-benign and sustainable alternative for artificial N2 fixation under ambient conditions, but needs materials to effectively catalyze the N2 reduction reaction (NRR). In this communication, we report that β-FeOOH nanorods behave as an efficient and durable NRR electrocatalyst. In 0.5 M LiClO4, such an electrocatalyst achieves a high NH3 yield of 23.32 μg h-1 mgcat.-1 and a faradaic efficiency of 6.7%, outperforming most reported aqueous-based NRR electrocatalysts under ambient conditions. Notably, this catalyst also shows good electrochemical stability and excellent selectivity. The catalytic mechanism of the NRR on the FeOOH(110) surface is further discussed using density functional theory calculations.