Nitrogen Fixation Efficiency Research Articles

A novel Zn-doped CHA zeolite coupled CDs for photocatalytic nitrogen fixation

The construction of zeolite/semiconductor was proved to be one of the effective ways to improve the photocatalytic performance. In this paper, CDs@Zn-CHA/CN was prepared by hydrothermal method, and a synergistic interaction was formed between CDs@Zn-CHA and CN to enhance the photocatalytic nitrogen fixation activity. The photoelectric properties characterization and XPS and in situ IR results indicated that CDs, Zn-CHA and CN formed a charge transfer interface, which improved the separation of photogenerated carriers and greatly enhanced the nitrogen fixation efficiency. Nitrogen is adsorbed by Zn-CHA with microporous structure and activated by contact with Zn sites on CHA. CN has a good visible light response and provides photogenerated carriers under visible light irradiation. CDs act on the interfacial charge transfer between Zn-CHA and CN, promoting the transfer of photogenerated electrons to the nitrogen adsorbed by Zn-CHA and accelerating the dissociation of NN, thus increasing the yield of NH3. Compared with CDs@Zn-CHA and CN, 10% CDs@Zn-CHA/CN achieved 5.82 and 2.99 times of nitrogen fixation yield, respectively. Furthermore, the higher hydrophobicity of CDs@Zn-CHA/CN was found by contact angle measurement, which provided more abundant three-phase contact points for the reaction process. This study provides new ideas and directions for the design of photocatalyst.

Gliding Arc Reactor under AC Pulsed Mode Operation: Spatial Performance Profile for NOx Synthesis.

A two-dimensional gliding arc reactor for NOx synthesis was investigated in this study using AC pulsed mode operation. Tests with a duty cycle of 40 or 60% achieved the lowest energy consumption of 6.95 MJ/mol, which is an improvement of 15% from the case of continuous operation. Based on the results achieved, a new method for analyzing the spatial profile of the reactor was presented. The reactor was divided into five zones along the arc propagation, and results indicated that the first zone and last zone of the gliding arc reactor had higher energy consumption (9.59 and 8.63 MJ/mol, respectively), while lower consumption was observed in the middle parts of the reactor with a minimum of 5.00 MJ/mol. Spatial-resolved optical emission spectra, the deduced electron density, and temperature indicated the nonuniformity in plasma properties, which corresponds to the NOx production performance across the reactor. This research provides information and discussion that can be used for understanding and optimization of gliding arc reactors toward efficient nitrogen fixation.

Integrating local polarization in hydrogen bonded organic frameworks for efficient photocatalytic nitrogen fixation

Elaborately designing stabilized hydrogen-bonded organic frameworks (HOFs) with higher charge transfer rate and abundant active sites for efficient photocatalytic nitrogen fixation are urgent and challenging. Herein, a micromolecular hydrogen-based triazole unit integrated into rigid perylene diimide based hydrogen-bonded organic framework (NPDI) has been elaborately designed. Experimental and theoretical results demonstrate that the flexibility and polar micromolecular group embedded in rigid framework not only stabilized HOFs frameworks, but also enhanced the local polarization, electron delocalization and the built-in electric field of HOFs, which greatly promotes exciton dissociation and the carrier transfer. Fortunately, NPDI has excellent photocatalytic nitrogen fixation rate (179 µmol h−1 g−1) and near-infrared NH4+ yield in pure water under ambient conditions. Our work offers deep insights into molecular level regulation for rationally designing efficient HOFs.

Efficient photocatalytic nitrogen fixation over novel 2D/2D Bi12O17Br2/ZnCr layered double hydroxide heterojunction

Herein, a novel ultrathin 2D/2D heterostructure, Bi12O17Br2 with oxygen vacancies/ZnCr layered double hydroxides (Vo-Bi12O17Br2/ZnCr-LDHs, Vo-BZ) is prepared by solvothermal and coprecipitation methods for photocatalytic reduction of N2 to NH3. The optimal 2D/2D Vo-BZ heterostructure photocatalyst shows production rate of ammonia production of 286.0 μmol·g−1·h−1. It is 12.5 and 3.6 times higher than that of pure ZnCr-LDHs and Vo-Bi12O17Br2. The improved photocatalytic nitrogen reduction performance is attributed to the intimate contact interface, matching bandgap structure, the shortened migration distance, and thus significantly improved separation and transfer efficiency of hole-electron pairs and light adsorption ability. The large number of oxygen vacancies and high specific surface promote the absorption, activation and deionization of N2 molecules. The theoretical simulation calculation indicates that the free energy of nitrogen molecules on the surface of Vo-BZ is favorable for the absorption and activation of N2 molecules. The existence of oxygen vacancies and formation of heterojunctions can dramatically reduce energy barrier of nitrogen molecule hydrogenation process to boost photocatalytic N2 reduction. This study provides a new idea for the development of efficient photocatalytic nitrogen fixing catalysts.

Composition Engineering Opens an Avenue Toward Efficient and Sustainable Nitrogen Fixation

In this work, we open an avenue toward rational design of potential efficient catalysts for sustainable ammonia synthesis through composition engineering strategy by exploiting the synergistic effects among the active sites as exemplified by diatomic metals anchored graphdiyne via the combination of hierarchical high‐throughput screening, first‐principles calculations, and molecular dynamics simulations. Totally 43 highly efficient catalysts feature ultralow onset potentials (|Uonset| ≤ 0.40 V) with Rh‐Hf and Rh‐Ta showing negligible onset potentials of 0 and −0.04 V, respectively. Extremely high catalytic activities of Rh‐Hf and Rh‐Ta can be ascribed to the synergistic effects. When forming heteronuclears, the combinations of relatively weak (such as Rh) and relatively strong (such as Hf or Ta) components usually lead to the optimal strengths of adsorption Gibbs free energies of reaction intermediates. The origin can be ascribed to the mediate d‐band centers of Rh‐Hf and Rh‐Ta, which lead to the optimal adsorption strengths of intermediates, thereby bringing the high catalytic activities. Our work provides a new and general strategy toward the architecture of highly efficient catalysts not only for electrocatalytic nitrogen reduction reaction (eNRR) but also for other important reactions. We expect that our work will boost both experimental and theoretical efforts in this direction.

What determines symbiotic nitrogen fixation efficiency in rhizobium: recent insights into Rhizobium leguminosarum.

Symbiotic nitrogen fixation (SNF) by rhizobium, a Gram-negative soil bacterium, is an essential component in the nitrogen cycle and is a sustainable green way to maintain soil fertility without chemical energy consumption. SNF, which results from the processes of nodulation, rhizobial infection, bacteroid differentiation and nitrogen-fixing reaction, requires the expression of various genes from both symbionts with adaptation to the changing environment. To achieve successful nitrogen fixation, rhizobia and their hosts cooperate closely for precise regulation of symbiotic genes, metabolic processes and internal environment homeostasis. Many researches have progressed to reveal the ample information about regulatory aspects of SNF during recent decades, but the major bottlenecks regarding improvement of nitrogen-fixing efficiency has proven to be complex. In this mini-review, we summarize recent advances that have contributed to understanding the rhizobial regulatory aspects that determine SNF efficiency, focusing on the coordinated regulatory mechanism of symbiotic genes, oxygen, carbon metabolism, amino acid metabolism, combined nitrogen, non-coding RNAs and internal environment homeostasis. Unraveling regulatory determinants of SNF in the nitrogen-fixing protagonist rhizobium is expected to promote an improvement of nitrogen-fixing efficiency in crop production.

Magnetic field stabilized atmospheric pressure plasma nitrogen fixation: Effect of electric field and gas temperature

In this paper, we investigate the influence of plasma characteristics on nitrogen fixation efficiency and explore the optimization of discharge parameters by utilizing a magnetic field stabilized atmospheric pressure plasma. The gas temperature and electric field of the plasma are maintained at a constant level and can be independently adjusted by controlling the discharge current, gas flow rate, and external magnetic field. The spatial distribution of the gas temperature of the plasma is measured by laser-induced Rayleigh scattering. The results show that reducing the electric field and gas temperature leads to an increase in NOx production. The optimal parameters for nitrogen fixation are identified as a discharge current of 55 mA, a gas flow rate of 6 l·min−1, and an O2 fraction of 40%. These settings result in the lowest recorded energy cost of 2.29 MJ·mol−1 and a NOx concentration of approximately 15 925 ppm. The stable characteristics of the magnetically stabilized atmospheric pressure plasma make it suitable for further investigations into the effect of plasma characteristics on nitrogen fixation.

Boron-doped graphene quantum dot/bismuth molybdate composite photocatalysts for efficient photocatalytic nitrogen fixation reactions

Bismuth molybdate (BMO) is a promising visible-driven photocatalyst and constructing heterojunctions in BMO-based materials is an effective way to enhance photocatalytic performance. In this study, boron-doped graphene quantum dots (BGQDs) were synthesized by one-step pyrolysis and carbonization, followed by the preparation of bismuth molybdate/boron-doped graphene quantum dots (BGQDs/BMO) heterojunction photocatalysts using in-situ growth method. The introduction of BGQDs significantly improved the photocatalytic nitrogen fixation activity under the irradiation of visible light and without scavengers. The highest NH3 yield was achieved with BGQDs/BMO-10, which was 3.48 times higher than pure phase BMO. This improvement was due to the formation of Z-scheme heterojunctions between BGQDs and BMO with the synergistic mechanism of interfacial charge transport and the generation of more protons. This study provides useful guidance for enhancing the visible-light nitrogen fixation performance of BMO materials.

Boron doped mesoporous g-C3N4 nanosheets: Boosting photocatalytic nitrogen fixation performance under visible light

A simple two-step method was used to prepare g-C3N4 nanosheets doped with B atoms. The multi-layer porous morphology prolongs the transmission pathway of visible light inside, thereby improving the ability to capture visible light. The doped photosensitive B atoms can decrease the original bandgap of g-C3N4 and increase the material's sensitivity to visible light. According to the findings, B/g-C3N4 performs superbly in photocatalytic nitrogen fixation, with the best performance being 2 wt% B/g-C3N4 (81.56 mol/L-1.h−1), which has a nitrogen fixation efficiency 2.44 times higher than g-C3N4 (33.52 mol/L-1.h−1). Additionally, 2 wt% B/g-C3N4 exhibits strong photocatalytic stability due to the doping of B atoms.

Anchoring heterometallic cluster on P-doped carbon nitride for efficient photocatalytic nitrogen fixation in water and air ambient

Light-driven nitrogen fixation to produce ammonia is a green and economical technology of nitrogen reduction but is still quite challenging, especially in an air atmosphere without any sacrificial reagents. Herein, we demonstrate efficient photocatalytic nitrogen fixation using water and air directly by loading lanthanide–transition metal (4f–3d) cluster NdCo3 on two-dimensional P-doped graphitic carbon nitrides (PCN) material surface. Benefiting from the increase in the number of nitrogen vacancies (NVs) and highly matched band gap structure and excellent hole trapping ability of clusters, the NdCo3/PCN photocatalyst exhibits efficient nitrogen reduction activity with 371 (in air) and 825 µmol h−1 g−1 (in pure nitrogen) without any sacrificial reagents. The introduction of potassium sulfate inhibits hydrogen production and promotes nitrogen reduction activation. This work suggests that anchoring precisely structured clusters on 2D materials may enhance photocatalytic nitrogen reduction under normal temperature and pressure.

Rhizobial nitrogen fixation efficiency shapes endosphere bacterial communities and Medicago truncatula host growth

BackgroundDespite the knowledge that the soil–plant–microbiome nexus is shaped by interactions amongst its members, very little is known about how individual symbioses regulate this shaping. Even less is known about how the agriculturally important symbiosis of nitrogen-fixing rhizobia with legumes is impacted according to soil type, yet this knowledge is crucial if we are to harness or improve it. We asked how the plant, soil and microbiome are modulated by symbiosis between the model legume Medicago truncatula and different strains of Sinorhizobium meliloti or Sinorhizobium medicae whose nitrogen-fixing efficiency varies, in three distinct soil types that differ in nutrient fertility, to examine the role of the soil environment upon the plant–microbe interaction during nodulation.ResultsThe outcome of symbiosis results in installment of a potentially beneficial microbiome that leads to increased nutrient uptake that is not simply proportional to soil nutrient abundance. A number of soil edaphic factors including Zn and Mo, and not just the classical N/P/K nutrients, group with microbial community changes, and alterations in the microbiome can be seen across different soil fertility types. Root endosphere emerged as the plant microhabitat more affected by this rhizobial efficiency-driven community reshaping, manifested by the accumulation of members of the phylum Actinobacteria. The plant in turn plays an active role in regulating its root community, including sanctioning low nitrogen efficiency rhizobial strains, leading to nodule senescence in particular plant–soil–rhizobia strain combinations.ConclusionsThe microbiome–soil–rhizobial dynamic strongly influences plant nutrient uptake and growth, with the endosphere and rhizosphere shaped differentially according to plant–rhizobial interactions with strains that vary in nitrogen-fixing efficiency levels. These results open up the possibility to select inoculation partners best suited for plant, soil type and microbial community.Dv-bX6Q_Z8DTbrQMTFWdQvVideo

Facile synthesis of Fe single-atom porous photocatalysts via direct metal atomization achieving efficient photocatalytic nitrogen fixation

Photocatalytic nitrogen fixation has been explored as a feasible pathway for ammonia synthesis. However, the convenient and efficient preparation of photocatalysts for nitrogen fixation remains a challenge. Meanwhile, the reaction pathway and mechanism of photocatalytic nitrogen fixation are unclear. Herein, single-atom Fe-porous g-C3N4 (FPx) samples were manufactured using a one-step anneal technique via bubble template and direct metal atomization. Characterization results indicate that FPx has a porous structure and single-atom Fe. The porous structure exposed more active centers. Simultaneously, single-atom Fe changes the adsorption mode of N2 from physical to chemical and turns the photocatalytic nitrogen fixation from the associative distal pathway to the associative alternating pathway. Consequently, without any sacrificial agent or cocatalysts, FPx presents a prominent increase in photocatalytic activity, reaching 62.42 µmol h−1 g−1, over fivefold larger than that of bulk g-C3N4. This work provides new insights into photocatalytic nitrogen fixation and achieves efficient N2 photoreduction by constructing single-atom photocatalysts.

In-situ construction of novel sulfur-vacancy-rich Bi/Bi2S3/SnS2 Z-scheme heterostructure photocatalysts for efficient Cr(VI) reduction and nitrogen fixation

Highly competent and economical photocatalysts are one of the most charming targets in environmental restoration and clean production. Herein, a novel sulfur-vacancy-rich Bi/Bi2S3/SnS2 Z-scheme heterostructure was constructed in situ and applied for the photoreduction Cr(VI) and nitrogen fixation. The fabricated Bi/Bi2S3/SnS2–2 exhibits the optimum photoreduction Cr(VI) performance with the efficiency of 94.5% within 15 min visible light irradiation. The remarkably enhanced catalytic efficiency derived from the synergistic effect of the construction of intimate contacted interface, abundant sulfur vacancy and surface plasmon resonance (SPR) effect of metal Bi. Meanwhile, the excellent photocatalytic nitrogen fixation property (96.4 μmol g–1 h–1) was achieved by Bi/Bi2S3/SnS2–2 under full solar illumination because sulfur vacancy could provide sufficient catalytic sites to accelerate the adsorption and nitrogen activation. The Z-scheme heterostructure was proposed to expound the photocatalytic mechanism. This work offers a new perspective on hierarchical heterostructure with plentiful vacancies for environmental remediation and energy development.

Biochar amendment reduces biological nitrogen fixation and nitrogen use efficiency in cadmium-contaminated paddy fields

Cadmium (Cd) contamination poses a considerable threat to human health through grain enrichment and limits biological nitrogen fixation (BNF) in paddy fields. Biochar has shown great potential for agricultural soil remediation because it inactivates Cd, but uncertainties remain as to how biochar amendments affect BNF and grain N use efficiency in paddies. To elucidate these issues, we investigated the effects of biochar amendment on the structure and function of diazotrophic bacterial communities in different rice growth stages in Cd-contaminated paddy fields, and evaluated the contribution of BNF to grain N use efficiency under biochar amendment. The results showed that biochar amendment significantly increased the abundance of diazotrophic bacteria in the tillering and jointing stages. Furthermore, the community structure of soil diazotrophic bacteria markedly changed with biochar amendment, with a significant reduction in the abundances of Euryarchaeota, Desulfobacterales (Proteobacteria), and Sphingomonadales (Bacteroidetes) in the tillering stage. Changes in the soil carbon/nitrogen (C/N) ratio was the main factor driving diazotrophic microbial community characteristics caused by the release of available C from biochar at the tillering stage, rather than the Cd. Moreover, biochar amendment increased the efficiency of BNF (especially for autotrophic N2 fixation) in the vegetative phase of rice growth. Notably, biochar amendment significantly decreased BNF efficiency during the filling stage and reduced grain N use efficiency. The limited available nutrients in biochar and the toxicity of polycyclic aromatics and phenols in biochar-derived dissolved organic matter were responsible for the varied impacts of biochar on BNF in different rice growth stages. For the first time, we report that biochar amendment in paddy soils reduces Cd toxicity but also inhibits BNF and thereby decreases N use efficiency. Therefore, before applying biochar to inactivate Cd in paddy fields, there should be a trade-off between agricultural production and ecological safety to achieve sustainable agriculture.

Heme catabolism mediated by heme oxygenase in uninfected interstitial cells enables efficient symbiotic nitrogen fixation in Lotus japonicus nodules.

Legume nodules produce large quantities of heme required for the synthesis of leghemoglobin (Lb) and other hemoproteins. Despite the crucial function of Lb in nitrogen fixation and the toxicity of free heme, the mechanisms of heme homeostasis remain elusive. Biochemical, cellular, and genetic approaches were used to study the role of heme oxygenases (HOs) in heme degradation in the model legume Lotus japonicus. Heme and biliverdin were quantified and localized, HOs were characterized, and knockout LORE1 and CRISPR/Cas9 mutants for LjHO1 were generated and phenotyped. We show that LjHO1, but not the LjHO2 isoform, is responsible for heme catabolism in nodules and identify biliverdin as the invivo product of the enzyme in senescing green nodules. Spatiotemporal expression analysis revealed that LjHO1 expression and biliverdin production are restricted to the plastids of uninfected interstitial cells. The nodules of ho1 mutants showed decreased nitrogen fixation, and the development of brown, rather than green, nodules during senescence. Increased superoxide production was observed in ho1 nodules, underscoring the importance of LjHO1 in antioxidant defense. We conclude that LjHO1 plays an essential role in degradation of Lb heme, uncovering a novel function of nodule plastids and uninfected interstitial cells in nitrogen fixation.

Enhanced artificial nitrogen fixation efficiency induced by construction of ternary TiO2/MIL-88A(Fe)/g-C3N4 Z-scheme heterojunction

Herein, a ternary TiO2/MIL-88A(Fe)/g-C3N4 heterojunction is successfully constructed through a facile hydrothermal strategy for enhancing solar energy harvesting and efficiency of catalytic nitrogen reduction induced by enlarged light absorption range, increasing interfacial charge transfer ability and desirable stability. Under the simulated sunlight irradiation, the N2 fixation experiment shows that the yield of NH3 reaches 1084.31 μmol/(g·h) over the TiO2/MIL-88A(Fe)/g-C3N4 photocatalyst, and the yield is significantly enhanced, which is 33.68 and 13.94 times that is higher than the pure TiO2 and g-C3N4, respectively. In a mean time, the excellent performance of the photocatalytic N2 fixation over the ternary TiO2/MIL-88A(Fe)/g-C3N4 is verified based on density function theory calculation and the decisive step over the composite is investigated by calculating Gibbs free energies of nitrogen reduction paths. The performance enhancement mechanism of TiO2/MIL-88A(Fe)/g-C3N4 is speculated, which indicates that the hybridized three-component system presents a desirable Z-scheme band alignment, resulting in the improvement of separation and transfer efficiency of photoinduced charge carriers. The article shows a new and high-efficiency TiO2/MIL-88A(Fe)/g-C3N4 photocatalysis for excellent nitrogen reduction ability.

Transcriptomic and Metabolomic Analyses Reveal the Roles of Flavonoids and Auxin on Peanut Nodulation.

Rhizobia form symbiotic relationships with legumes, fixing atmospheric nitrogen into a plant-accessible form within their root nodules. Nitrogen fixation is vital for sustainable soil improvements in agriculture. Peanut (Arachis hypogaea) is a leguminous crop whose nodulation mechanism requires further elucidation. In this study, comprehensive transcriptomic and metabolomic analyses were conducted to assess the differences between a non-nodulating peanut variety and a nodulating peanut variety. Total RNA was extracted from peanut roots, then first-strand and second-strand cDNA were synthesized and purified. After sequencing adaptors were added to the fragments, the cDNA libraries were sequenced. Our transcriptomic analysis identified 3362 differentially expressed genes (DEGs) between the two varieties. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that the DEGs were mainly involved in metabolic pathways, hormone signal transduction, secondary metabolic biosynthesis, phenylpropanoid biosynthesis, or ABC transport. Further analyses indicated that the biosynthesis of flavonoids, such as isoflavones, flavonols, and flavonoids, was important for peanut nodulation. A lack of flavonoid transport into the rhizosphere (soil) could prevent rhizobial chemotaxis and the activation of their nodulation genes. The downregulation of AUXIN-RESPONSE FACTOR (ARF) genes and lower auxin content could reduce rhizobia's invasion of peanut roots, ultimately reducing nodule formation. Auxin is the major hormone that influences the cell-cycle initiation and progression required for nodule initiation and accumulates during different stages of nodule development. These findings lay the foundation for subsequent research into the nitrogen-fixation efficiency of peanut nodules.

Evaluation of Legume-Rhizobial Symbiotic Interactions Beyond Nitrogen Fixation That Help the Host Survival and Diversification in Hostile Environments.

Plants often experience unfavorable conditions during their life cycle that impact their growth and sometimes their survival. A temporary phase of such stress, which can result from heavy metals, drought, salinity, or extremes of temperature or pH, can cause mild to enormous damage to the plant depending on its duration and intensity. Besides environmental stress, plants are the target of many microbial pathogens, causing diseases of varying severity. In plants that harbor mutualistic bacteria, stress can affect the symbiotic interaction and its outcome. To achieve the full potential of a symbiotic relationship between the host and rhizobia, it is important that the host plant maintains good growth characteristics and stay healthy under challenging environmental conditions. The host plant cannot provide good accommodation for the symbiont if it is infested with diseases and prone to other predators. Because the bacterium relies on metabolites for survival and multiplication, it is in its best interests to keep the host plant as stress-free as possible and to keep the supply stable. Although plants have developed many mitigation strategies to cope with stress, the symbiotic bacterium has developed the capability to augment the plant's defense mechanisms against environmental stress. They also provide the host with protection against certain diseases. The protective features of rhizobial-host interaction along with nitrogen fixation appear to have played a significant role in legume diversification. When considering a legume-rhizobial symbiosis, extra benefits to the host are sometimes overlooked in favor of the symbionts' nitrogen fixation efficiency. This review examines all of those additional considerations of a symbiotic interaction that enable the host to withstand a wide range of stresses, enabling plant survival under hostile regimes. In addition, the review focuses on the rhizosphere microbiome, which has emerged as a strong pillar of evolutionary reserve to equip the symbiotic interaction in the interests of both the rhizobia and host. The evaluation would draw the researchers' attention to the symbiotic relationship as being advantageous to the host plant as a whole and the role it plays in the plant's adaptation to unfavorable environmental conditions.

Highly efficient visible-light photocatalytic nitrogen fixation via single-atom iron catalyst site and synergistic effect of Zr-cluster in zirconium-based porphyrinic metal-organic frameworks (PCN-222)

Zirconium-based porphyrinic metal-organic frameworks (MOFs), including PCN-222 (nonmetal), and PCN-222 (Fe) were employed as the photocatalyst for photocatalytic nitrogen (N2) fixation to NH3 under visible light irradiation. The as-synthesized MOFs of PCN-222 (nonmetal) and PCN-222 (Fe) exhibited a notable increase in photocatalytic N2 fixation compared to the pure (Metallo) porphyrin ligands of H2TCPP and FeTCPP, respectively. The comparative studies illustrated that using the Zr-cluster as a stable node and the active redox site is a successful strategy to increase the stability and photocatalytic activity of the MOF-based photocatalysts. On the other, the single-atom Fe site as an active center of absorption and activation of nitrogen molecules improved the N2 fixation activity. Remarkably, among them all, PCN-222 (Fe) demonstrated the highest photocatalytic N2 fixation activity with a rate of 1502.51 μmol g-1h−1 which could be related to the simultaneous presence of Zr-cluster and single-atom Fe site which promote the performance of the photocatalyst. So, the photocatalytic activity of PCN-222 (Fe) is 1.9 and 2.5 times higher than the activity of PCN-222 (nonmetal) and pure FeTCPP, respectively. High photocatalytic activity, sacrificial agent-free conditions, excellent efficiency in short response time, reusability, and mild reaction conditions are the attractive characteristics of the as-synthesized photocatalysts that make them suitable candidates for photocatalytic NH3 production.

Unique Tubular BiOBr/g-C3 N4 Heterojunction with Efficient Separation of Charge Carriers for Photocatalytic Nitrogen Fixation.

The industrial ammonia synthesis process consumes a lot of energy and causes serious environmental pollution. As a sustainable approach for ammonia synthesis, photocatalytic nitrogen reduction employing water as the reducing agent has a lot of potential. A simple surfactant-assisted solvothermal method is used to synthesize g-C3 N4 nanotubes with flower-like spherical BiOBr grown inside and outside (BiOBr/g-C3 N4 , BC). The hollow tubular structure realizes the full use of visible light by the multi-scattering effect of light. Large surface areas and more active sites for N2 adsorption and activation are present in the distinctive spatially dispersed hierarchical structures. Particularly, the quick separation and transfer of electrons and holes are facilitated by the sandwich tubular heterojunctions and tight contact interface of BiOBr and g-C3 N4 . The maximal NH3 generation rate of the BiOBr/g-C3 N4 composite catalysts can reach 255.04 μmol⋅ g-1 ⋅ h-1 , and it is 13.9 and 5.8 times that of pure BiOBr and g-C3 N4 . This work provides a novel method for designing and constructing unique heterojunctions for efficient photocatalytic nitrogen fixation.