Advances in molybdenum-containing photocatalysts for nitrogen fixation.

Light-driven nitrogen fixation catalyzed by nanomaterials: link between PNF and BNF.

Ammonia, as the second most-produced chemical worldwide, serves diverse roles in the industrial and agricultural sectors. However, its conventional production via the Haber–Bosch process poses significant challenges, including high energy consumption and carbon dioxide emissions. In contrast, photocatalytic nitrogen (N2) fixation, utilizing solar energy with minimal emissions, offers a promising method for sustainable ammonia synthesis. Despite ongoing efforts, photocatalytic nitrogen fixation catalysts continue to encounter challenges such as inadequate N2 adsorption, limited light absorption, and rapid photocarrier recombination. This review explores how the electronic structure and surface characteristics of one-dimensional nanomaterials could mitigate these challenges, making them promising photocatalysts for N2 fixation. The review delves into the underlying photocatalytic mechanisms of nitrogen fixation and various synthesis methods for one-dimensional nanomaterials. Additionally, it highlights the role of the high surface area of one-dimensional nanomaterials in enhancing photocatalytic performance. A comparative analysis of the photocatalytic nitrogen fixation capabilities of different one-dimensional nanomaterials is provided. Lastly, the review offers insights into potential future advancements in photocatalytic nitrogen fixation.

Enhancing the separation efficiency of photogenerated charge carriers and suppressing the competition of the hydrogen evolution reaction (HER) are potential methods to improve the activity of photocatalytic nitrogen fixation. In this study, a BiOBr/hydrophobic carbon cloth (HCC) heterojunction with an internal electric field (IEF) has been successfully fabricated through a one-step solvent method. The IEF facilitates the migration of photogenerated electrons from BiOBr to the HCC. Concurrently, the HCC provides an N2-rich environment, thereby suppressing the competitive HER. Theoretical calculations reveal that N2 adsorbs on the Bi atom surface, with HCC acting as an electron transfer medium. Photogenerated electrons are transferred from HCC to the distal N atom, enhancing its activation and reducing the energy barrier of the rate-determining step. The nitrogen fixation yield of BiOBr/HCC is 202.2µmol g-1 h-1. The ammonia produced by BiOBr/HCC has been successfully applied in the hydroponic experiment of pennywort, which confirms its non-toxicity and growth-promoting effects. The synthesis of BiOBr/HCC heterojunctions with superior nitrogen fixation capabilities has opened new avenues for the application of BiOBr-based catalysts in the field of nitrogen fixation, potentially leading to widespread use in agricultural production in the future.

High-efficiency electron tandem flow mode on carbon nitride/titanium dioxide heterojunction for visible light nitrogen photofixation

Photocatalytic nitrogen fixation offers a pathway for clean, sustainable, and decentralized ammonia production, which can be an alternative to the capital and energy intensive Haber-Bosch process. Antimony molybdate (Sb2MoO6) is a promising material for photocatalytic nitrogen fixation. However, the typical hydrothermal synthesis method generally leads to poor crystallinity and consequent poor photoactivity. In this work, mechanical chemical method is adopted to massively synthesize highly crystalline Sb2MoO6. Defects and chemical composition of photocatalyst have been engineered to maximize photocatalytic activity toward nitrogen fixation. Findings of this work would help understand photocatalytic mechanism of metal oxides in nitrogen fixation, which has an implication in development of new photocatalysts.

Photocatalytic nitrogen fixation has the potential to provide a greener route for producing nitrogen-based fertilizers under ambient conditions. Computational screening is a promising route to discover new materials for the nitrogen fixation process, but requires identifying "descriptors" that can be efficiently computed. In this work, we argue that selectivity toward the adsorption of molecular nitrogen and oxygen can act as a key descriptor. A catalyst that can selectively adsorb nitrogen and resist poisoning of oxygen and other molecules present in air has the potential to facilitate the nitrogen fixation process under ambient conditions. We provide a framework for active site screening based on multifidelity density functional theory (DFT) calculations for a range of metal oxides, oxyborides, and oxyphosphides. The screening methodology consists of initial low-fidelity fixed geometry calculations and a second screening in which more expensive geometry optimizations were performed. The approach identifies promising active sites on several TiO2 polymorph surfaces and a VBO4 surface, and the full nitrogen reduction pathway is studied with the BEEF-vdW and HSE06 functionals on two active sites. The findings suggest that metastable TiO2 polymorphs may play a role in photocatalytic nitrogen fixation, and that VBO4 may be an interesting material for further studies.

The availability of soil Molybdenum (Mo) especially for acid soil is scarcely found, while their existency determines the process of Nitrogen fixation. Mo is the component of meta-protein nitrogenase which helps the process of biological nitrogen fixation and acts as essential component which needed for N bacteria metabolism. The nitrogenase enzyme needs Mo element in the process of its metabolism, which acts as electron carrier between oxidized and reduction stages. The deficiency of Mo has been reported in several crops, with various appearance, such as chlorosis or yellowish leaves. The paper describes the role of Mo in biological nitrogen fixation. Key words: Symbiotic fixation, molybdenum, legume, nitrogenase

In this study, Fe-doped graphitic carbon nitride (Fe-MCNC) with varying Fe contents was synthesized via a supramolecular approach, followed by thermal exfoliation, and was then used for accelerated photocatalytic hydrogen evolution and nitrogen fixation. Various techniques were used to study the physicochemical properties of the MCN (g-C3N4 from melamine) and Fe-MCNC (MCN for g-C3N4 and C for cyanuric acid) catalysts. The field emission scanning electron microscopy (FE-SEM) images clearly demonstrate that the morphology of Fe-MCNC changes from planar sheets to porous, partially twisted (partially developed nanotube and nanorod) nanostructures. The elemental mapping study confirms the uniform distribution of Fe on the MCNC surface. The X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy (UV-DRS) results suggest that the Fe species might exist in the Fe3+ state and form Fe-N bonds with N atoms, thereby extending the visible light absorption areas and decreasing the band gap of MCN. Furthermore, doping with precise amounts of Fe might induce exfoliation and increase the specific surface area, but excessive Fe could destroy the MCN structure. The optimized Fe-MCNC nanostructure had a specific surface area of 23.6 m2 g-1, which was 8.1 times greater than that of MCN (2.89 m2 g-1). To study its photocatalytic properties, the nanostructure was tested for photocatalytic hydrogen evolution and nitrogen fixation; 2Fe-MCNC shows the highest photocatalytic activity, which is approximately 13.3 times and 2.4 times better, respectively, than MCN-1H. Due to its high efficiency and stability, the Fe-MCNC nanostructure is a promising and ideal photocatalyst for a wide range of applications.

Asymmetric Fe-O2-Ti structures accelerate reduced-layer-FeII “electron” conversion: Facilitating photocatalytic nitrogen fixation

Nitrogen fixation from air at normal temperature and pressure via Cobalt-iron photocatalyst day and night

Fe-carbon dots enhance the photocatalytic nitrogen fixation activity of TiO2@CN heterojunction

Electronic structures fundamentally influence material properties, with electron spin playing a pivotal role in defining catalytic activity and reaction pathways. However, the precise spin-mediated mechanisms of adsorption energies and nitrogen-nitrogen transition states on the catalyst surface, remain unclear due to the complexity of spin-mediated promotion factors. Herein, we demonstrate that tuning the spin state of single iron (Fe) sites on TiO2 can significantly enhance photocatalytic nitrogen reduction reaction (NRR). Our theoretical predictions reveal that low spin states of single Fe sites facilitate N2 adsorption and intermediate formation, thereby activating more catalytic sites on TiO2 for efficient nitrogen fixation. By manipulating the crystal phase and incorporating fluorine dopants, we systematically modulate the spin states of Fe sites, achieving optimized N2 adsorption and desorption kinetics and suppressing charge recombination. Experimental results combined with density functional theory (DFT) calculations confirm that these modifications reduce the magnetic moment of Fe sites, lower free energy barriers, and strengthen electronic interactions with key intermediates, particularly during N─NH formation. Intriguingly, we find that weakening N2 adsorption via reduced Fe magnetization enhances catalytic performance, challenging conventional assumptions that stronger N─N bond activation necessarily improves NRR efficiency. Our experimental results corroborate these findings, showing a remarkable 72-fold increase in ammonia production rate compared to pristine TiO2. This work highlights the crucial role of electron spin engineering in designing highly efficient NRR catalysts and provides a new paradigm for rational catalyst design.

Atomic-level active sites steering in ultrathin photocatalysts to trigger high efficiency nitrogen fixation

Biological nitrogen fixation (BNF) is a pivotal process that reduces nitrogen to ammonium within the nitrogen cycle. Extracellular electron transfer (EET) between diazotrophs and the extracellular environment influences the occurrence and efficiency of BNF. Although extracellular electron acceptors can function as a component of the electron transport chain, providing energy for chemotrophic nitrogen fixation via extracellular respiration, the function and mechanism of outward EET in photosynthetic diazotrophs remain unclear. Here, using Rhodopseudomonas palustris TIE‐1, a photosynthetic bioelectrochemical nitrogen fixation system is established for simultaneous nitrogen fixation and current generation, to dissect the complex interaction between these two processes. Outward EET functions are found to maintain redox balance, rather than serving as an extracellular respiration pathway. It significantly suppresses BNF by competing with nitrogenase for electrons. Lumichrome serves as the primary electron shuttle for indirect electron transfer, while cytochromes play an important role in direct electron transfer. Notably, the pio operon participates in outward EET. This study reveals the interaction mechanism between photosynthetic BNF and outward EET, providing new insight into the regulatory mechanisms of nitrogen fixation in anoxygenic phototrophs across diverse environmental conditions.

The rapid pace of economic and industrial development has led to increasingly severe environmental pollution and energy scarcity, emerging as pressing global concerns. Photocatalysis represents a promising strategy for addressing these dual challenges by converting solar energy into chemical energy or degrading pollutants. Among various photocatalysts, bismuth molybdate (Bi2MoO6), a representative Aurivillius-phase material, has garnered considerable attention owing to its visible-light-responsive bandgap, low toxicity, cost-effectiveness, and outstanding chemical stability. However, its practical application is significantly constrained by inherent drawbacks, including limited light absorption range and rapid recombination of photogenerated electron–hole pairs. This review presents a comprehensive overview of recent advances in Bi2MoO6-based photocatalysts, systematically examining synthesis methods, modification strategies (such as heterojunction construction, defect engineering, and elemental doping), and their diverse applications in both environmental remediation and energy conversion. Specifically, the environmental applications encompass the degradation of organic pollutants (e.g., dyes and antibiotics), antibacterial activity, and performance in complex water matrices. In the energy sector, applications include photocatalytic hydrogen evolution, CO2 reduction, and nitrogen fixation. Finally, the current challenges and future research directions for enhancing the photocatalytic performance of Bi2MoO6 are discussed, with the aim of guiding further investigation and facilitating its practical implementation in sustainable environmental and energy technologies.