Nitrate Reduction Activity Research Articles

The influences of mangrove grown on sedimentary nitrate reduction activities are more pronounced in sandy coasts compared to muddy coasts

The influences of mangrove grown on sedimentary nitrate reduction activities are more pronounced in sandy coasts compared to muddy coasts

Anomalous CatalyticPerformance on Non-Active-Site Carbon Substrate.

Carbon-based nanomaterials are gaining attention in electrocatalysis. This study investigates the inherent nitrate reduction activity (NO3RR) of commercial carbon paper as a substrate. Results showed that carbon paper, without additional catalysts, achieved approximately 80.42% NH3Faradaic efficiency (FE) at -2.1 V vs. Hg/HgO in alkaline conditions, 83.51% NH3FE at -1.9 V vs. Ag/AgCl in neutral conditions, and 14.53% NH3FE at -1.9 V vs. MSE in acidic conditions. Density Functional Theory (DFT) calculations revealed energy barriers of 2.66 eV, 0.95 eV, and 1.37 eV, respectively. Molecular physisorption on the carbon paper surface generates an induced electric field, promoting charge transfer between the carbon paper and the adsorbed molecules, thus enhancing the activity of the carbon paper. These findings highlight the importance of considering the intrinsic catalytic properties of carbon substrates in catalyst design and evaluation, as overlooking these properties can lead to inaccurate performance assessments. This study emphasizes the need for a comprehensive approach to optimize catalytic systems.

Unveiling the Dual Role of Oxophilic Cr4+ in Cr-Cu2O Nanosheet Arrays for Enhanced Nitrate Electroreduction to Ammonia.

Cuprous oxide (Cu2O)-based catalysts present a promising activity for the electrochemical nitrate (NO3-) reduction to ammonia (eNO3RA), but the electrochemical instability of Cu+ species may lead to an unsatisfactory durability, hindering the exploration of the structure-performance relationship. Herein, we propose an efficient strategy to stabilize Cu+ through the incorporation of Cr4+ into the Cu2O matrix to construct a Cr4+-O-Cu+ network structure. In situ and quasi-in situ characterizations reveal that the Cu+ species are well maintained via the strong Cr4+-O-Cu+ interaction that inhibits the leaching of lattice oxygen. Importantly, in situ generated Cr3+-O-Cu+ from Cr4+-O-Cu+ is identified as a dual-active site for eNO3RA, wherein the Cu+ sites are responsible for the activation of N-containing intermediates, while the assisting Cr3+ centers serve as the electron-proton mediators for rapid water dissociation. Theoretical investigations further demonstrated that the metastable state Cr3+-O-Cu+ favors the conversion from the endoergic hydrogenation of the key *ON intermediate to an exoergic reaction in an ONH pathway, and facilitates the subsequent NH3 desorption with a low energy barrier. The superior eNO3RA with a maximum 91.6% Faradaic efficiency could also be coupled with anodic sulfion oxidation to achieve concurrent NH3 production and sulfur recovery with reduced energy input.

Unveiling the Dual Role of Oxophilic Cr4+ in Cr‐Cu2O Nanosheet Arrays for Enhanced Nitrate Electroreduction to Ammonia

Cuprous oxide (Cu2O)‐based catalysts present a promising activity for the electrochemical nitrate (NO3‐) reduction to ammonia (eNO3RA), but the electrochemical instability of Cu+ species may lead to an unsatisfactory durability, hindering the exploration of the structure‐performance relationship. Herein, we propose an efficient strategy to stabilize Cu+ through the incorporation of Cr4+ into the Cu2O matrix to construct a Cr4+‐O‐Cu+ network structure. In situ and quasi‐in situ characterizations reveal that the Cu+ species are well maintained via the strong Cr4+‐O‐Cu+ interaction that inhibits the leaching of lattice oxygen. Importantly, in situ generated Cr3+‐O‐Cu+ from Cr4+‐O‐Cu+ is identified as a dual‐active site for eNO3RA, wherein the Cu+ sites are responsible for the activation of N‐containing intermediates, while the assisting Cr3+ centers serve as the electron‐proton mediators for rapid water dissociation. Theoretical investigations further demonstrated that the metastable state Cr3+‐O‐Cu+ favors the conversion from the endoergic hydrogenation of the key *ON intermediate to an exoergic reaction in an ONH pathway, and facilitates the subsequent NH3 desorption with a low energy barrier. The superior eNO3RA with a maximum 91.6% Faradaic efficiency could also be coupled with anodic sulfion oxidation to achieve concurrent NH3 production and sulfur recovery with reduced energy input.

Enhanced Electrocatalytic Activity for Nitrate Reduction to Ammonia by Tuning a Ruthenium Oxidation State of Ruthenium-Based Nanotubes

Enhanced Electrocatalytic Activity for Nitrate Reduction to Ammonia by Tuning a Ruthenium Oxidation State of Ruthenium-Based Nanotubes

Isolation and Characterisation of Pink Pigmented Facultative Methylotrophs (PPFM) from Malaysian Ulam Leaves

This study aims to isolate and characterise the Pink Pigmented Facultative Methylotrophs (PPFM) bacteria from the leaves of common Malaysian table salad (ulam). The colonies of PPFM bacteria were obtained using selectively modified Pseudomonas agar based on the appearance of the pink pigment colony. The three selected isolates labelled OJ4, OJ154 [Oenanthe javanica (Blume) DC.] and ML8 [from Melicope lunu-ankenda (Gaertn.) T. G. Hartley] were chosen for characterisation. The result showed the PPFM bacteria colonies (log CFU/g) at the leaf surface of C. caudatus are 4.4 ± 0.1, significantly higher than O. javanica, 3.8 ± 0.2, and M. lunu-ankenda, 3.2 ± 0.1. The selected isolates belong to the Gram-negative group, motile with rod shape with size [length (l) × width (w)] in µm unit 4.3 ± 1.1 × 1.6 ± 0.6, 5.4 ± 0.2 × 1.2 ± 0.1, and 3.5 ± 0.7 × 1.0 ± 0.0, respectively. They show positive urease, catalase, and oxidase activities, while none of them can degrade starch, gelatine, or cellulose, as well as glucose fermentation (MR test) and metabolism actions (VP test), producing indole and hydrogen sulphide gaseous. Only isolate OJ154 demonstrates positive casein hydrolysis and nitrate reduction activities, while only isolate ML8 can utilise citrate but not in lipid degradation. Their sequence analysis of the 16S rRNA indicated that OJ4 and ML8 are Methylobacterium radiotolerans with a similarity of 99%, whereas, OJ154 is Methylorubrum salsuginis with a similarity of 99%. To conclude, PPFM bacteria from the leaves of C. caudatus, O. javanica, and M. lunu-ankenda have been isolated and characterised in particular.

Alternative Oxidase Alleviates Mitochondrial Oxidative Stress during Limited Nitrate Reduction in Arabidopsis thaliana.

The conversion of nitrate to ammonium, i.e., nitrate reduction, is a major consumer of reductants in plants. Previous studies have reported that the mitochondrial alternative oxidase (AOX) is upregulated under limited nitrate reduction conditions, including no/low nitrate or when ammonium is the sole nitrogen (N) source. Electron transfer from ubiquinone to AOX bypasses the proton-pumping complexes III and IV, thereby consuming reductants efficiently. Thus, upregulated AOX under limited nitrate reduction may dissipate excessive reductants and thereby attenuate oxidative stress. Nevertheless, so far there is no firm evidence for this hypothesis due to the lack of experimental systems to analyze the direct relationship between nitrate reduction and AOX. We therefore developed a novel culturing system for A. thaliana that manipulates shoot activities of nitrate reduction and AOX separately without causing N starvation, ammonium toxicity, or lack of nitrate signal. Using shoots processed with this system, we examined genome-wide gene expression and growth to better understand the relationship between AOX and nitrate reduction. The results showed that, only when nitrate reduction was limited, AOX deficiency significantly upregulated genes involved in mitochondrial oxidative stress, reductant shuttles, and non-phosphorylating bypasses of the respiratory chain, and inhibited growth. Thus, we conclude that AOX alleviates mitochondrial oxidative stress and sustains plant growth under limited nitrate reduction.

(Invited) Efficient Recycling of Dilute Nitrate to Ammonia Using Cu-Based Electrocatalyst

The use of nitrogen fertilizers has contributed significantly to the growth of agricultural production, but the nitrogen use efficiency is typically lower than 40%, so most of the nitrogen readily leaches into ground water, rivers, and lakes, causing an increase of nitrate (NO3 −) concentration and severe environmental problems. Electrochemical reduction of nitrate has emerged as a promising route for the recycling of nitrate from wastewater and sustainable production of ammonia when powered by renewable electricity. Here I present our recent studies of the intrinsic activity and selectivity of Cu for nitrate electroreduction, as well as a rational design of Cu-based catalysts for single-pass conversion of nitrate to ammonia. Using polycrystalline Cu foils for benchmarking, we elucidated the impact of often overlooked factors on nitrate reduction, including Cu facet exposure, nitrate concentration, and electrode surface area. We find that an electropolished Cu foil exhibits a higher activity and selectivity for nitrate reduction to ammonia than a wet-etched Cu foil, benefiting from a greater exposure of Cu(100) facets that are more favorable for the reaction. The NH3 selectivity shows no apparent dependence on the nitrate concentration, but it increases monotonically with Cu electrode area, which is attributed to a promoted conversion of intermediately produced NO2 − to NH3 on a larger electrode. Based on the understandings, we further developed a Cu/Co-based tandem electrocatalyst, which achieved nearly 100% single-pass conversion of dilute nitrate (5−50 mM) to NH3 at a low overpotential using a flow cell.

Electrocatalytically active and charged natural chalcopyrite for nitrate-contaminated wastewater purification extended to energy storage Zn-NO3− battery

Charged natural chalcopyrite (CuFeS2, Ncpy) was developed for a three-dimensional electrochemical nitrate reduction (3D ENO3−RR) system with carbon fiber cloth cathode and Ti/IrO2 anode and Zn-NO3− battery. The 3D ENO3−RR system with Ncpy particle electrodes (PEs) possessed superior nitrate removal of 95.6 % and N2 selectivity of 76 % with excellent reusability under a broad pH range of 2–13 involving heterogeneous and homogeneous radical mechanisms. The Zn-NO3− battery with Ncpy cathode delivered an open-circuit voltage of 1.03 V and a cycling stability over 210 h. It was found that Ncpy PEs functioned through self-oxidation, surface dynamic reconstruction (Cu1.02Fe1.0S1.72O1.66 to Cu0.61Fe1.0S0.27O2.98), intrinsic micro-electric field (CuI, S2− anodic and FeIII cathodic poles), and reactive species (•OH, SO4•−, 1O2, •O2− and •H) generation. Computational analyses reveal that CuFeS2(112) surface with the lowest surface energy preferentially exposes Fe and Cu atoms. Cu site is beneficial for reducing NO3− to NO2−, Fe and Fe−Cu dual sites are conducive to N2 selectivity, lowering the overall reaction barriers. It paves the way for selective NO3− reduction in wastewater treatment and can be further extended to energy storage devices by utilizing low-cost Ncpy.

Roseibium algae sp. nov., isolated from a marine alga (Grateloupia sp.).

A novel Gram-stain-negative, rod-shaped, non-spore-forming, aerobic, motile bacterium with a single polar or subpolar flagellum, designated strain H3510T, was isolated from marine alga collected on sea shore of Yantai, PR China. The organism grew optimally at 28 °C and pH 7.0 and in presence of 3.0 % (w/v) NaCl. The strain exhibited positive catalase activity but negative oxidase and nitrate reduction activities. The predominant cellular fatty acids were C18 : 1 ω7c and/or C18 : 1 ω6c, 11-methyl C18 : 1 ω7c, and C16 : 0. Additionally, the major polar lipids were phosphatidylglycerol, phosphatidylmonomethylethanolamine, diphosphatidylglycerol, and phosphatidylethanolamine; the respiratory quinone was ubiquinone 10 (Q-10). The genomic DNA G+C content of strain H3510T was 54.2%. The novel strain showed the closest relationship with Roseibium polysiphoniae KMM 9699T with 98.2 % 16S rRNA gene sequence similarity. The calculated values for average nucleotide identity and DNA-DNA hybridization between strain H3510T and the phylogenetically related Roseibium species were in the range of 71.3-74.9 % and 13.7-19.9 %, respectively. Based on polyphasic analyses, strain H3510T was identified as representing a novel species of the genus Roseibium, for which the name Roseibium algae sp. nov. is proposed. The type strain is H3510T (=KCTC 8206T=MCCC 1K04325T). The heterologously expressed inositol 2-dehydrogenase gene from strain H3510T displayed high oxidation activity on myo-inositol and showed potential in the production of rare stereoisomers of inositol, such as scyllo-inositol.

Red Carbon Mediated Formation of Cu2O Clusters Dispersed on the Oxocarbon Framework by Fehling's Route and their Use for the Nitrate Electroreduction in Acidic Conditions.

The oligomers of carbon suboxide, known as red carbon, exhibit a highly conjugated structure and semiconducting properties. Upon mild heat treatment, it transforms into a carbonaceous framework rich in oxygen surface terminations, called oxocarbon. In this study, the abundant oxygen functionalities are harnessed as anchors to create oxocarbon-supported nanohybrid electrocatalysts. Starting with single atomic Cu (II) strongly coordinated to oxygen atoms on red carbon, the Fehling reaction leads to the formation of Cu2O clusters. Simultaneously, a covalent oxocarbon framework emerges via cross-linking, providing robust support for Cu2O clusters. Notably, the oxocarbon support effectively stabilizes Cu2O clusters of very small size, ensuring their high durability in acidic conditions and the presence of ammonia. The synthesized material exhibits a superior electrocatalytic activity for nitrate reduction under acidic electrolyte conditions, with a high yield rate of ammonium (NH4 +) at 3.31mmolh-1mgcat -1 and a Faradaic efficiency of 92.5% at a potential of -0.4V (vs RHE).

The synergistic tandem effect of Cu2+1O and Co3O4 enhances the activity and selectivity of nitrate reduction to ammonia in neutral solution

Construction the electrocatalysts with multiple components is an effective strategy to enhance the activity for NH3 generation in electrocatalytic nitrate reduction reaction (NITRR). Herein, we report a high performance electrocatalyst Co3O4-Cu2+1O/CF. The obtained Co3O4-Cu2+1O/CF nanosheets not only provide large active surface area but also construct the bimetal oxides interface for exerting Cu-Co tandem catalysis. Meanwhile, Co3O4-Cu2+1O/CF exhibits a maximum NH3-Faradaic efficiency of 96.5% and NH3 yield of 0.26 mmol h−1 cm−2 in neutral solution with 10 mM NO3-. The control experiments and Tafel analysis clearly manifest the tandem catalysis mechanism on Co3O4-Cu2+1O/CF, where Cu2+1O favors the NO3- conversion to NO2-, while Co3O4 selectively promotes NO2- conversion to NH3. The DFT calculations reveal that the strengthened NO3- adsorption and the enhanced adsorption of H* on Co3O4-Cu2+1O/CF jointly promote the selective formation of ammonia from NO3- reduction. This work provides the strategy of constructing the efficient transition metal composited electrocatalysts in NITRR.

Highly efficient electrolytic reduction of nitrate to produce ammonia using Cu@Ni2P-NF Schottky heterojunction

Electrolytic reduction of nitrate to produce ammonia (NO3-RR) is one of the very promising alternatives to the energy-consuming Haber-Bosch process. The catalytic activity of nitrate reduction can be effectively improved by tuning the electronic structure and interfacial electron transfer. In this work, Cu@Ni2P-NF metal- semiconductor heterostructure is designed to adjust the adsorption of H* while enhance the adsorption of NO3- through schottky contacts. It is shown that the synergistic effects realized by the built-in electric field could effectively improve the NO3-RR catalytic performance. In the electrolytic cell with 1 M KOH and 20 mM KNO3, the ammonia yield at –0.2 V (vs. RHE) reaches 0.374 mmol∙h−1∙cm−2, and the nitrate removal efficiency is up to 94.63% with a selectivity of 90.25%. The energy conversion is realized by applying a Zn-NO3- battery with power density of 5.09 mW∙cm−2. This work demonstrates that the design of metal-semiconductor schottky heterojunction is an effective way to obtain novel electrocatalysts for NO3-RR.

Atomic Force Microscopy (AFM) Tip based Nanoelectrode with Hydrogel Electrolyte and Application to Single-Nanoparticle Electrochemistry

<p>An unconventional fabrication technique of nanoelectrode was developed using atomic force microscopy (AFM) and hydrogel. Until now, the precise control of electroactive area down to a few nm<sup>2</sup> has always been an obstacle, which limits the wide application of nanoelectrodes. Here, the nanometer-sized contact between the boron-doped diamond (BDD) as conductive AFM tip and the agarose hydrogel as solid electrolyte was well governed by the feedback amplitude of oscillation in the non-contact mode of AFM. Consequently, this low-cost and feasible approach gives rise to new possibilities for the fabrication of nanoelectrodes. The electroactive area controlled by the set point of AFM was investigated by cyclic voltammetry (CV) of the ferrocenmethanol (FcMeOH) combined with quasi-solid agarose hydrogel as an electrolyte. Single copper (Cu) nanoparticle was deposited at the apex of the AFM tip using this platform whose electrocatalytic activity for nitrate reduction was then investigated by CV and Field Emission-Scanning Electron Microscopy (FE-SEM), respectively.</p>

Lot-to-lot variation in the microbiota during the brewing process of kimoto-type Japanese rice wine.

Kimoto-type Japanese rice wine (sake) has a wide variety of flavors, as the predominant microbes, including lactic acid bacteria (LAB) and nitrate-reducing bacteria, that spontaneously proliferate in the fermentation starter vary depending on the brewery. In this study, we traced the microbiota in four lots of starters manufactured in a newly established brewery and evaluated the lot-to-lot variation and characteristics of the microbiota in the brewery. The results of a 16S ribosomal RNA amplicon analysis showed that the starters brewed in the second brewing year had a more diverse microbiota than those in the first brewing year. Among the LAB predominated at the middle production stage, lactococci, including Leuconostoc spp., were detected in all the lots, while lactobacilli predominated for the first time in the second year. These results suggest that repeated brewing increased microbial diversity and altered the microbial transition pattern in the kimoto-style fermentation starters. Phylogenetic analyses for the LAB isolates from each starter identified Leuconostoc suionicum, Leuconostoc citreum, and Leuconostoc mesenteroides as predominant lactococci as well as a unique lactobacillus in place of Latilactobacillus sakei. We also found that a rice koji-derived Staphylococcus gallinarum with nitrate-reducing activity was generally predominant during the early production stage, suggesting that there was a case in which staphylococci played a role in nitrite production in the starters. These findings are expected to contribute to the understanding of the diversity of microbiota in kimoto-type sake brewing and enable control of the microbiota for consistent sake quality.

Regulating intermediate adsorption and H2O dissociation on a diatomic catalyst to promote electrocatalytic nitrate reduction to ammonia

Cu–Fe–N–C demonstrates excellent electrocatalytic activity for nitrate reduction by optimizing intermediate adsorption and generating a substantial supply of H* for the thorough hydrogenation of the N-containing intermediates.

Electrochemical nitrate reduction in acid enables high-efficiency ammonia synthesis and high-voltage pollutes-based fuel cells

Most current research is devoted to electrochemical nitrate reduction reaction for ammonia synthesis under alkaline/neutral media while the investigation of nitrate reduction under acidic conditions is rarely reported. In this work, we demonstrate the potential of TiO2 nanosheet with intrinsically poor hydrogen-evolution activity for selective and rapid nitrate reduction to ammonia under acidic conditions. Hybridized with iron phthalocyanine, the resulting catalyst displays remarkably improved efficiency toward ammonia formation owing to the enhanced nitrate adsorption, suppressed hydrogen evolution and lowered energy barrier for the rate-determining step. Then, an alkaline-acid hybrid Zn-nitrate battery was developed with high open-circuit voltage of 1.99 V and power density of 91.4 mW cm–2. Further, the environmental sulfur recovery can be powered by above hybrid battery and the hydrazine-nitrate fuel cell can be developed for simultaneously hydrazine/nitrate conversion and electricity generation. This work demonstrates the attractive potential of acidic nitrate reduction for ammonia electrosynthesis and broadens the field of energy conversion.

Study on the effectiveness and mechanism of a sustainable dual slow-release model to improve N utilization efficiency and reduce N pollution in black soil

Long-term intensive cultivation has led to serious N loss and low N fertilizer utilization efficiency (NUE) in black soil areas. The lost N is not only a waste of resources but also a serious pollution threat to the environment, leading to the decline in water quality and food safety and the greenhouse effect. In the present study, a stable dual slow-release model, CPCS-Urea, was prepared by in situ polymerization using nitrapyrin, urea and melamine-formaldehyde resin as raw materials. The effect of the dual slow-release model was systematically evaluated using two consecutive years of field experiments. Five treatments were established in the field experiment: no N fertilizer (N0), urea (N180), 1 % CPEC-Urea, 0.5 % CPCS-Urea, and 1 % CPCS-Urea. The results showed that the new dual slow-release CPCS-Urea model outperformed both the use of urea and the traditional slow-release CPEC-Urea model in reducing N losses and improving NUE. The application of CPCS-Urea reduced nitrate (NO3−) leaching by 28.2 %–47.2 % and N2O emissions by 36.5 %–42.4 % and increased NUE by 20.7 %–28.5 % compared to urea application. The CPCS-Urea model modulated the activity of ammonia-oxidizing bacteria (AOB) and dissimilatory nitrate reduction to ammonium (DNRA) bacteria in soil, showing a significant decrease in AOB activity and an increase in DNRA activity. This results in a lower soil NO3−-N yield and a 53.1 %–72.0 % increase in NH4+-N content, providing sufficient N for the entire growth and development cycle of maize. In short, the dual slow-release CPCS-Urea model has great application prospects for promoting agricultural development in black soil areas.

The pH dependence of the electrocatalytic nitrate reduction by tin-modified palladium(100) electrodes: Effects of structures of tin species and protonation of nitrite

Nitrate is a common pollutant in groundwater and endangers drinking water safety. The electrocatalytic nitrate reduction using tin-modified palladium electrode (Sn/Pd) provided a promising alternative for nitrate removal. However, the pH effect on the nitrate reduction activity of Sn/Pd and its mechanistic insights are still unclear. In this study, Sn/Pd(100) single crystalline electrodes were used as a model electrode to understand the pH effect on its nitrate and nitrite reduction activity and mechanism. Sn/Pd(100) electrodes showed the nitrate reduction activity at pH < 3.8. DFT calculations suggest that Sn2+ site can be found on Pd(100) at pH < 3.8 and promote nitrate adsorption. The copresence of Sn and Pd sites can reduce the LUMO energy of the adsorbed nitrate molecule and decrease the van der Waals electrostatic potential of the O-N bond, which promotes electron injection and protonation to nitrate. At pH > 3.8, on the other hand, the formation of Sn(OH)+ or Sn(OH)2 can inhibit the adsorption of NO3− on Sn atoms, resulting in the disappearance of the electrocatalytic activity. Sn atomic sites mainly promote the reduction step of NO3− → NO2−, and the subsequent NO2– reduction reaction occurs on Pd sites. The protonation of NO2– was crucial to the nitrite reduction on Pd(100) surface. The findings in this study would be useful to develop highly active electrocatalysts based on Sn and Pd materials for the nitrate reduction.

Unraveling the potential of native Azotobacter and Azospirillum spp. formulations for sustainable crop production of rice (Oryza sativa L. var. Khandagiri)

Biological nitrogen fixation is significantly effective and sustainable field procedure for the promotion of plant growth & development and reducing the burden of chemical fertilizers. In the present investigation, plant growth promoting activities of indigenous bio-fertilizer formulations of Azotobacter and Azospirillum spp. isolated from rice pots filled with local soil of Odisha was examined. The efficacy of Azotobacter and Azospirillum spp. were assessed by selecting five isolates from each genus that were analyzed by biochemical assay like utilization and fermentation of carbohydrate, citrate, nitrate reduction activity, oxidase activity, catalase activity and phosphatase activity. The isolates (Az2 and As5) showed maximum PGP activities among all the isolates of Azotobacter and Azospirillum spp. The analyzed isolates showed variation in production of ethylene between 63.11 ± 4.23 to 121.09 ± 4.56 nmole C2H4/mg bact./h. The isolates Az2 and As5 among Azotobacter and Azospirillum spp. respectively fixed more nitrogen in culture which is 101.66 ± 9.79 (Az2) nmole and 121.09 ± 4.56 (As5) nmole C2H4/mg bact./h. The treatments T1 (Az2) and T2 (As5) were used as individual application of Azotobacter and Azospirillum spp. and T3 as combined application of both the strains which had the best response in all of the developmental metrics studied. Among all treatments, T3 performed around 23-27% better than the T1 and T2 individually.