High NH3 Yield Research Articles

Interfacial Engineering to Fabricate Nanoporous FeMo Bimetallic Nitride for Enhanced Electrochemical Ammonia Synthesis.

The electrochemical N2 reduction reaction (NRR) currently represents a green and sustainable approach to ammonia production. However, the further progress of NRR is significantly hampered by poor catalytic activity and selectivity, necessitating the development of efficient and stable electrocatalysts. Herein, a nanoporous Fe-Mo bimetallic nitride (Fe3N-MoN) is synthesized using a molten-salt preparation method. This catalyst demonstrates notable NRR performance, achieving a high NH3 yield rate of 45.1µgh-1mg-1 and a Faradaic efficiency (FE) of 26.5% at -0.2V (vs RHE) under ambient conditions. Detailed experimental studies and density functional theory (DFT) calculations reveal that the fabricated interface between Fe3N and MoN effectively modulates the surface electronic structure of the catalyst. The interface induces an increase in the degree of electron deficiency at the nitrogen-vacancy sites on the catalyst surface, allowing N2 molecules to occupy the nitrogen vacancies more easily, thereby promoting N2 adsorption/activation during the NRR process. Consequently, the Fe3N-MoN catalyst exhibits outstanding NRR activity. The insights gained from fabricating the Fe3N-MoN interface in this work pave the way for further development of interfacial engineering to prepare high-efficient electrocatalyst.

Iron and nickel based alloy nanoparticles anchored on phosphorus-modified carbon-nitrogen plane enhances electrochemical nitrate reduction to ammonia

The catalysts of iron and nickel nanoparticles anchored on carbon–nitrogen plane (FeNi-CN) are considered as the potential candidates for promising electrochemical nitrate reduction to ammonia (ENO3RR). However, the high d-orbital energy levels of iron and nickel sites coordinated with nitrogen atoms often lead to overly strong adsorption of reaction intermediates on active sites, severely limiting the improvement of catalytic performance. Herein, a catalyst FeNi3@P-NC consisting FeNi3 alloy nanoparticles confined in phosphorus (P)-modified carbon–nitrogen plane is successfully fabricated, where the electron withdrawal effect induced by P on the carbon–nitrogen plane decreases the d-orbital energy, and optimizes the d-band center of FeNi alloy, thus weakening the overly strong adsorption of intermediates at the metal-N sites and thereby improving NO3RR activity. The prepared FeNi3@P-NC catalyst exhibits exceptional NO3RR performance with a 93 ± 4.5 % Faradaic efficiency of NH3 production (FENH3) and a high NH3 yield rate (YNH3) of 9633 ± 227.3 μg h−1 cm−2 at −0.7 V versus Reversible Hydrogen Electrode (vs. RHE) under alkaline medium. Importantly, FeNi3@P-NC also demonstrates superior catalytic stability and durability, which maintains stability over twenty-five successive electrochemical cycles and for 50 h of continuous electrolysis at 100 mA cm−2.

Electrochemical Synthesis of Metasequoia-Like Reduced Graphene Oxide Coated Cobalt-Silver Catalyst for Stable and Efficient Electrocatalytic Nitrate Reduction to Ammonia.

Electrocatalytic nitrate (NO3 -) reduction to ammonia (NH3) is a green and efficient NH3synthesis technology. Metallic silver (Ag) is one of the well-known electrocatalysts for NO3 - reduction. However, under alkaline conditions, its poor water-splitting ability fails to provide sufficient protonic hydrogen required for NH3 synthesis, resulting in low NH3 selectivity. Additionally, metal catalysts are prone to leaching and oxidation during electrocatalysis, resulting in poor stability. Herein, cobalt (Co) into Ag (CoAg) catalyst is doped, which not only increases the NH3 selectivity by 34.4%, but also reduces the reduction potential by 0.1V. Meanwhile, reduced graphene oxide (rGO) as a protective "armor" is used to encapsulate the CoAg catalyst (rGO2.92@CoAg). The rGO2.92@CoAg catalyst shows excellent stability for over 300 hours (h) of continuous reaction. The Co and Ag contents in the rGO2.92@CoAg catalyst after continuous tests decreases by only 4.3% and 3.1%, respectively, which are much lower than those of the CoAg catalyst without the rGO (90.8%, 52.6%). Moreover, the rGO2.92@CoAg catalyst shows high Faradaic efficiency (99.3%) and NH3 yield rate (1.47mmol h-1 cm-2). Therefore, a high performance and strong stability rGO2.92@CoAg catalyst is obtained by Co doping and rGO coating, which provides theoretical basis for practical industrial application.

Modulating Nitrogen Adsorption Mode and Microenvironment of Active Sites for Boosting Electrochemical Nitrogen Reduction.

Electrochemical reduction of N2(NRR) offers a sustainable approach for ammonia (NH3) synthesis, serving as a complementary to the traditional emission- and energy-intensive Haber-Bosch process. However, it faces challenges in N2 activation and competing with pronounced hydrogen evolution reaction (HER). Herein an efficient electrocatalyst comprised of ultrafine Ru nanoclusters (NCs) confined by a hydrophobic molecular layer is developed on the surface of 2D Ti3C2Tx for NRR. These experimental and theoretical calculation results demonstrate that 1) ultrafine Ru NCs dispersed on the Ti3C2Tx surface form paired active sites for N2 chemisorption in a unique tilted configuration with low-energy activation 2) the hydrophobic molecular layer modulates the local microenvironment surrounding catalytically active sites, enabling efficient N2 accumulation while repelling H2O diffusion to the active sites on the Ti3C2Tx surface, thereby leading to an increased N2 concentration and suppressed HER. As a result, an exceptionally high NH3 yield rate of 33.5µg h-1mg-1cat and Faradaic efficiency of 65.3% are obtained at -0.25V versus reversible hydrogen electrode (RHE) in 0.1m Na2SO4, outperforming those previously reported Ti3C2Tx-derived electrocatalysts. This work provides a valuable strategy for the rational design of advanced electrocatalysts by manipulating active sites and local microenvironments for efficient electrocatalysis.

Coherent NiS2@SnS2nanosheet for accelerating electrocatalytic nitrate reduction to ammonia.

The development of an effective and selective catalyst is the key to improving the multi-electron transfer nitrate reduction reaction (NO3-RR) to ammonia. Here, we synthesized a coherent NiS2@SnS2nanosheet catalyst loaded on carbon cloth via one-step solvothermal method. Experimental data reveals that the integration of NiS2and SnS2can enhance the NO3-RR performance in terms of high NH3yield rate of 408.2μg h-1cm-2and Faradaic efficiency of 89.61%, as well as satisfying cycling and long-time stability.

Promoted Two-Step Ammonia Synthesis with CoOOH/Co foam at Ampere-Level Current Density and Nearly 100% Faraday Efficiency from Air and Water.

Ammonia (NH3) is regarded as an essential hydrogen storage material in the new energy field, and plasma-electrocatalytic synthesis of NH3 (PESA) is an alternative to the traditional Haber-Bosch process. Here, a bifunctional catalyst CoOOH/CF is proposed to enhance the PESA process. Benefiting from the efficient activation of O2 by CoOOH/CF, NOx - yield rate can reach the highest value of 171.90mmol h-1 to date. Additionally, CoOOH holds a more negative d-band center, thereby exhibiting weaker adsorption toward NO*, lowering the energy barrier for the rate determining step, resulting in a high NH3 yield rate (302.55mg h-1 cm-2 at -0.8V) with ampere-level NH3 current density (2.86 A cm-2 at -0.8V) and nearly 100% Faraday efficiency (FE, 99.8% at -0.6V). Moreover, CoOOH/CF achieves an excellent 4.54g h-1 NH3 yield rate with 97.9% FE in an enlarged electrolyzer, demonstrating the feasibility of PESA on a large scale.

Oxygen vacancy-rich Fe2O3/Co3O4 heterostructure electrocatalyst promotes N2 activation for efficient nitrogen reduction

The adsorption and activation of N2 as well as the competitive hydrogen evolution reaction (HER) pose significant challenges to the electrocatalytic nitrogen reduction reaction (ENRR), which severely limits its industrial application. Therefore, exploring the ENRR electrocatalysts with high activity and selectivity is an extremely important task. In this work, the oxygen vacancy-rich Fe2O3/Co3O4 heterostructures (referred to as Vo-X-Fe2O3/Co3O4) were rationally designed by employing Co3O4 as a template via a simple hydrothermal and subsequent calcination method, which acted as highly efficient ENRR electrocatalysts. The electrocatalytic activity of Vo-X-Fe2O3/Co3O4 can be easily regulated by optimization of the Fe content and the introduction of oxygen vacancy (Vo). The results demonstrate that the optimized Vo-1.0-Fe2O3/Co3O4 catalyst achieves a high NH3 yield of 47.37 μg h−1 mgcat−1 and a Faradaic efficiency (FE) of 22.42 %. Moreover, the excellent stability and reproducibility are also demonstrated. The comprehensive characterizations reveal that the exceptional performance of Vo-1.0-Fe2O3/Co3O4 can be attributed to the improved N2 adsorption and activation, restricted competitive HER and promoted electron transfer kinetics induced by the synergistic introduction of Vo and Fe. This work emerged a new speculating orientation for rational design of ENRR catalysts.

Electrocatalytic nitrite conversion to ammonia over Mn single atoms anchored on MoO3-x

Electrocatalytic reduction of NO2 to NH3 (NO2RR) offers a promising route to attain harmful NO2– removal and valuable NH3 production. Herein, Mn single atoms anchored on oxygen vacancy-rich MoO3-x (Mn1/MoO3-x) are developed as a high-performance catalyst for the NO2RR. Atom characterizations unravel that the isolated Mn atoms exist as Mn1-O5 moieties on MoO3-x. Theoretical calculations and in situ electrochemical spectroscopic measurements unveil that Mn1/MoO3-x follows a Langmuir-Hinshelwood mechanism to drive the NO2RR process, in which Mn1-O5 site facilitates the adsorption and activation of NO2– to form the intermediates, while MoO3-x substrate dissociates H2O to yield *H. The generated *H is then transferred from MoO3-x substrate to Mn1-O5 site which promotes the intermediate protonation to produce NH3. Remarkably, Mn1/MoO3-x in flow cell reaches the high NH3 yield rate of 546.25 μmol h−1 cm−2 and NH3-Faraday efficiency of 92.6 %, outperforming most reported NO2RR catalysts.

Co–Ni bimetallic oxide with tuned surface oxygen vacancies efficiently electrocatalytic reduction of nitrate to ammonia

The electrocatalytic reduction reaction of nitrate (NO3−) to ammonia (NH3) provides an efficient and clean NH3 production method, which has the potential to replace the traditional industrial preparation methods. However, the limited activity and Faraday efficiency (FE) of existing catalysts impede the practical application of this technology. Herein, in this work, a high-performance catalyst with high NH3 yield and FE was fabricated. Co–Ni bimetallic oxide (NiCo2O4) catalysts with tuned surface oxygen vacancies (OVs) contents were prepared by changing the heating rate during calcination, NiCo2O4 calcined at a heating rate of 5 °C/min (NiCo2O4-5) possessed the highest surface OVs content. Experimental studies showed that NiCo2O4 with higher surface OVs had better NO3RR activity, inhibited the production of nitrite (NO2−), and exhibited higher selectivity to NH3. Among prepared catalysts, NiCo2O4-5 demonstrated superior performance in electrocatalytic reduction of NO3− to NH3, achieving a high NH3 FE (94.4 %) and yield (193.2 mmol/h g−1) at a suitable applied voltage. Besides, in situ Fourier transform infrared spectroscopy analysis suggested that NiCo2O4-5 preferentially followed the NO3RR pathway as follows: *NO3 → *HNO3 → *NO2 → *HNO2 → *NO → *HNO → *N → *NH → *NH2 → *NH3.

Tandem Effect Promotes MXene‐Supported Dual‐Site Janus Nanoparticles for High‐Efficiency Nitrate Reduction to Ammonia and Energy Output through Zn‐Nitrate Battery

AbstractElectrocatalytic nitrate reduction reaction (NO3RR) can convert nitrate contaminants into ammonia with higher added value. However, due to the NO3RR involving complex multi‐electron reactions, there is an urgent need to develop efficient electrocatalysts. Herein, CoCu Janus nanoparticles loaded on Ti3C2Tx MXene (CoCu‐Ti3C2Tx) is synthesized via the combination of molten salt etching and galvanic replacement strategy. The tandem catalysis of CoCu Janus NPs can maintain the balance between nitrogenous intermediates and active hydrogen (Hads). CoCu‐Ti3C2Tx exhibits a high NH3 yield of 8.08 mg h−1 mgcat.−1 and a satisfactory Faradaic efficiency of 93.6% at −0.7 V versus reversible hydrogen electrode (RHE). The Zn‐NO3− battery assembled with CoCu‐Ti3C2Tx shows an excellent power density of 10.33 mW cm−2, an NH3 yield of 1.52 mg h−1 mgcat.−1 and a Faradaic efficiency of 95.3% at 10 mA cm−2, which enables the simultaneous elimination of nitrate pollutants, ammonia production, and energy supply. Moreover, a series of verification experiments and density functional theory calculation are combined to reveal the reaction path and tandem catalytic mechanism. This work not only provides a new inspiration for the design of tandem catalysts but also promotes the development of Zn‐nitrate battery.

Spin Manipulation of Co sites in Co9S8/Nb2CTx Mott-Schottky Heterojunction for Boosting the Electrocatalytic Nitrogen Reduction Reaction.

Regulating the adsorption of an intermediate on an electrocatalyst by manipulating the electron spin state of the transition metal is of great significance for promoting the activation of inert nitrogen molecules (N2) during the electrocatalytic nitrogen reduction reaction (eNRR). However, achieving this remains challenging. Herein, a novel 2D/2D Mott-Schottky heterojunction, Co9S8/Nb2CTx-P, is developed as an eNRR catalyst. This is achieved through the in situ growth of cobalt sulfide (Co9S8) nanosheets over a Nb2CTx MXene using a solution plasma modification method. Transformation of the Co spin state from low (t2g 6eg 1) to high (t2g 5eg 2) is achieved by adjusting the interface electronic structure and sulfur vacancy of Co9S8/Nb2CTx-P. The adsorption ability of N2 is optimized through high spin Co(II) with more unpaired electrons, significantly accelerating the *N2→*NNH kinetic process. The Co9S8/Nb2CTx-P exhibits a high NH3 yield of 62.62µg h-1 mgcat. -1 and a Faradaic efficiency (FE) of 30.33% at -0.40V versus the reversible hydrogen electrode (RHE) in 0.1m HCl. Additionally, it achieves an NH3 yield of 41.47µg h-1 mgcat. -1 and FE of 23.19% at -0.60V versus RHE in 0.1m Na2SO4. This work demonstrates a promising strategy for constructing heterojunction electrocatalysts for efficient eNRR.

Cu/CuxO/Graphdiyne Tandem Catalyst for Efficient Electrocatalytic Nitrate Reduction to Ammonia.

The electrocatalytic reduction reaction of nitrate (NO3 -) to ammonia (NH3) is a feasible way to achieve artificial nitrogen cycle. However, the low yield rate and poor selectivity toward NH3 product is a technical challenge. Here a graphdiyne (GDY)-based tandem catalyst featuring Cu/CuxO nanoparticles anchored to GDY support (termed Cu/CuxO/GDY) for efficient electrocatalytic NO3 - reduction is presented. A high NH3 yield rate of 25.4mg h-1 mgcat. -1 (25.4mg h-1 cm-2) with a Faradaic efficiency of 99.8% at an applied potential of -0.8V versus RHE using the designed catalyst is achieved. These performance metrics outperform most reported NO3 - to NH3 catalysts in the alkaline media. Electrochemical measurements and density functional theory reveal that the NO3 - preferentially attacks Cu/CuxO, and the GDY can effectively catalyze the reduction of NO2 - to NH3. This work highlights the efficacy of GDY as a new class of tandem catalysts for the artificial nitrogen cycle and provides powerful guidelines for the design of tandem electrocatalysts.

Spatially Separated Cu/Ru on Ordered Mesoporous Carbon for Superior Ammonia Electrosynthesis from Nitrate over a Wide Potential Window.

Nitrate (NO3-) in wastewater poses a serious threat to human health and the ecological environment. The electrocatalytic NO3- reduction to ammonia (NH3) reaction (NO3-RR) emerges as a promising carbon-free energy route for enabling NO3- removal and sustainable NH3 synthesis. However, it remains a challenge to achieve high Faraday efficiencies at a wide potential window due to the complex multiple-electron reduction process. Herein, spatially separated dual-metal tandem electrocatalysts made of a nitrogen-doped ordered mesoporous carbon support with ultrasmall and high-content Cu nanoparticles encapsulated inside and large and low-content Ru nanoparticles dispersed on the external surface (denoted as Ru/Cu@NOMC) are designed. In electrocatalytic NO3-RR, the Cu sites can quickly convert NO3- to adsorbed NO2- (*NO2-), while the Ru sites can efficiently produce active hydrogen (*H) to enhance the kinetics of converting *NO2- to NH3 on the Cu sites. Due to the synergistic effect between the Cu and Ru sites, Ru/Cu@NOMC exhibits a maximum NH3 Faradaic efficiency (FENH3) of approximately 100% at -0.1 V vs reversible hydrogen electrode (RHE) and a high NH3 yield rate of 1267 mmol gcat-1 h-1 at -0.5 V vs RHE. Finite element method (FEM) simulation and electrochemical in situ Raman spectroscopy revealed that the mesoporous framework can enhance the intermediate concentration due to the in situ confinement effect. Thanks to the Cu-Ru synergistic effect and the mesopore confinement effect, a wide potential window of approximately 500 mV for FENH3 over 90% and a superior stability for NH3 production over 156 h can be achieved on the Ru/Cu@NOMC catalyst.

Promoting active hydrogen supply for kinetically matched tandem electrocatalytic nitrate reduction to ammonia

Electrocatalytic nitrate reduction (NO3RR) shows admirable potential for environmental remediation and producing valuable NH3. However, the catalyst is restricted by the kinetic mismatch between NO3--to-NO2- and NO2--to-NH3, which results in excess NO2- and poor NH3 selectivity. Herein, a kinetically matched tandem electrocatalytic strategy with tunable active hydrogen(*H) supply is designed. The combination of Cu2O and Co11(HPO3)8(OH)6 (CoPO) playing key roles in NO3RR by i) on-demand supply of *H from CoPO; ii) the electronically coupled interface between Cu2O and CoPO enhance *H transfer kinetics. The Cu2O-CoPO-2 exhibits high NH3 yield of 22 mg cm−2 h−1 with Faradaic efficiency of 95 % at −0.37 V vs. RHE. In situ characterizations indicate the dynamic equilibrium between *H production and consumption contributes to high NO3RR performance. The techno-economic analyses reveal the system is economically viable compared to Haber-Bosch (H-B) process, which benefits from industrial current densities and superior energy efficiency at low potentials.

A high-performance electrocatalyst for sustainable ammonia synthesis via single-atom Ru-embedded Fe2O3 nitrogen-DOPED carbon

Ammonia (NH3) is an important industrial chemical, but the production of NH3 by the conventional Haber-Bosch process consumes large amounts of energy and has a serious environmental impact. Electrochemical nitrogen reduction reaction (NRR) offers a promising green alternative, but challenges remain in developing efficient catalysts. Here, we report the synthesis of single-atom Ru-embedded metal–organic framework-derived Fe2O3 nitrogen-doped carbon (Ru/Fe2O3-NC) materials via plasma-enhanced chemical vapour deposition. Under ambient conditions, the Ru/Fe2O3-NC catalyst exhibited a high NH3 yield rate of 141.18 μg h−1 mgcat.−1 in 0.1 M K2SO4 with a Faraday efficiency (FE) of 48.89 %, which was superior to the pristine Fe2O3-NC catalyst. Online differential electrochemical mass spectrometry (DEMS) analysis confirmed the selective generation of NH3 and no by-product N2H4 was detected. The Ru/Fe2O3-NC catalyst also showed remarkable stability during prolonged electrolysis. This work demonstrates the synergistic effect of incorporating single-atomic Ru in the Fe2O3-NC framework and provides a new platform for the development of advanced catalysts for the efficient and sustainable electrochemical synthesis of NH3.

A General Strategy Based on Hetero‐Charge Coupling Effect for Constructing Single‐Atom Sites

AbstractSingle‐atom catalysts have emerged as cutting‐edge hotspots in the field of material science owing to their excellent catalytic performance brought about by well‐defined metal single‐atom sites (M SASs). However, huge challenges still lie in achieving the rational design and precise synthesis of M SASs. Herein, we report a novel synthesis strategy based on the hetero‐charge coupling effect (HCCE) to prepare M SASs loaded on N and S co‐doped porous carbon (M1/NSC). The proposed strategy was widely applied to prepare 17 types of M1/NSC composed of single or multi‐metal with the integrated regulation of the coordination environment and electronic structure, exhibiting good universality and flexible adjustability. Furthermore, this strategy provided a low‐cost method of efficiently synthesizing M1/NSC with high yields, that can produce more than 50 g catalyst at one time, which is key to large‐scale production. Among various as‐prepared unary M1/NSC (M can be Fe, Co, Ni, V, Cr, Mn, Mo, Pd, W, Re, Ir, Pt, or Bi) catalysts, Fe1/NSC delivered excellent performance for electrocatalytic nitrate reduction to NH3 with high NH3 Faradaic efficiency of 86.6 % and high NH3 yield rate of 1.50 mg h−1 mgcat.−1 at −0.6 V vs. RHE. Even using Fe1/NSC as a cathode in a Zn‐nitrate battery, it exhibited a high open circuit voltage of 1.756 V and high energy density of 4.42 mW cm−2 with good cycling stability.

A General Strategy Based on Hetero-Charge Coupling Effect for Constructing Single-Atom Sites.

Single-atom catalysts have emerged as cutting-edge hotspots in the field of material science owing to their excellent catalytic performance brought about by well-defined metal single-atom sites (M SASs). However, huge challenges still lie in achieving the rational design and precise synthesis of M SASs. Herein, we report a novel synthesis strategy based on the hetero-charge coupling effect (HCCE) to prepare M SASs loaded on N and S co-doped porous carbon (M1/NSC). The proposed strategy was widely applied to prepare 17 types of M1/NSC composed of single or multi-metal with the integrated regulation of the coordination environment and electronic structure, exhibiting good universality and flexible adjustability. Furthermore, this strategy provided a low-cost method of efficiently synthesizing M1/NSC with high yields, that can produce more than 50 g catalyst at one time, which is key to large-scale production. Among various as-prepared unary M1/NSC (M can be Fe, Co, Ni, V, Cr, Mn, Mo, Pd, W, Re, Ir, Pt, or Bi) catalysts, Fe1/NSC delivered excellent performance for electrocatalytic nitrate reduction to NH3 with high NH3 Faradaic efficiency of 86.6 % and high NH3 yield rate of 1.50 mg h-1 mgcat. -1 at -0.6 V vs. RHE. Even using Fe1/NSC as a cathode in a Zn-nitrate battery, it exhibited a high open circuit voltage of 1.756 V and high energy density of 4.42 mW cm-2 with good cycling stability.

CuCo2O4/CuO Heterostructure with Oxygen Vacancies Induced by Plasma for Electrocatalytic Nitrate Reduction to Ammonia.

Electrochemical nitrate reduction (NO3RR) to ammonia production is regarded as one of the potential alternatives for replacing the Haber-Bosch technology for realizing artificial ammonia synthesis. In this study, a CuCo2O4/CuO-Ar heterostructure in the shape of dandelion nanospheres formed by nanoarrays has been successfully constructed, demonstrating excellent NO3RR performance. Experimental results indicate that Ar plasma etching of CuCo2O4/CuO-Ar significantly increases the content of oxygen vacancies compared to the sample of CuCo2O4/CuO-Air etched by air plasma, resulting in improved NO3RR performance. Density functional theory calculations further confirm that the existence of more oxygen vacancies effectively decreases the energy barrier of nitrate adsorption, which is due to the generation of more oxygen vacancies facilitating nitrate adsorption and weakening the N-O bonds of nitrate after plasma treatment. As a result, CuCo2O4/CuO-Ar exhibits a high NH3 yield of 0.55 mmol h-1 cm-2 and a Faraday efficiency of 95.07% at the optimal potential of -0.9 V (vs RHE) in a neutral medium. Importantly, CuCo2O4/CuO-Ar also showcases excellent electrocatalytic stability. This study presents new views on the design and structure regulation of NO3RR electrocatalysts and their potential applications in the future.

Polynuclear Cobalt Cluster-Based Coordination Polymers for Efficient Nitrate-to-Ammonia Electroreduction.

The electrocatalytic nitrate reduction reaction (NITRR) holds great promise for purifying wastewater and producing valuable ammonia (NH3). However, the lack of efficient electrocatalysts has impeded the achievement of highly selective NH3 synthesis from the NITRR. In this study, we report the design and synthesis of two polynuclear Co-cluster-based coordination polymers, {[Co2(TCPPDA)(H2O)5]·(H2O)9(DMF)} and {Co1.5(TCPPDA)[(CH3)2NH2]·(H2O)6(DMF)2} (namely, NJUZ-2 and NJUZ-3), which possess distinct coordination motifs with well-defined porosity, high-density catalytic sites, accessible mass transfer channels, and nanoconfined chemical environments. Benefitting from their intriguing multicore metal-organic coordination framework structures, NJUZ-2 and NJUZ-3 exhibit remarkable catalytic activities for the NITRR. At a potential of -0.8 V (vs. RHE) in an H-type cell, they achieve an optimal Faradaic efficiency of approximately 98.5% and high long-term durability for selective NH3 production. Furthermore, the electrocatalytic performance is well maintained even under strongly acidic conditions. When operated under an industrially relevant current density of 469.9 mA cm-2 in a flow cell, a high NH3 yield rate of up to 3370.6 mmol h-1 g-1cat. was observed at -0.5 V (vs. RHE), which is 20.1-fold higher than that obtained in H-type cells under the same conditions. Extensive experimental analyses, in combination with theoretical computations, reveal that the great enhancement of the NITRR activity is attributed to the preferential adsorption of NO3- and the reduction in energy input required for the hydrogenation of *NO3 and *NO2 intermediates.

Vacancy engineering of BiFeO3 perovskite for low-barrier electrochemical nitrogen fixation

Because of its environmental and intrinsic benefits, the nitrogen reduction reaction (NRR) using electrocatalysts has garnered significant attention. Engineering on the surface is commonly utilized to improve electrocatalytic activity by introducing atomic defects. In this study, we have developed a successful strategy to promote nitrogen activation by introducing oxygen vacancies into BiFeO3 perovskite. BiFeO3 with oxygen vacancies (denoted as VO-BiFeO3) possesses a high NH3 yield rate (89.3 μg h−1 mgcat−1) and Faradaic efficiency (FE) (13.5 %) at −0.40 V versus the reversible hydrogen electrode (RHE). According to density functional theory (DFT) calculations, the introduction of oxygen vacancies increases the binding capacity for nitrogen immobilization and reduces the energy barrier for the rate-determining step of NRR. Moreover, the analysis of the thermodynamic limiting potentials towards N2 reduction and H2 evolution demonstrates that VO-BiFeO3 has a higher selectivity for NRR than pristine BiFeO3.