New opportunities for efficient N2 fixation by nanosheet photocatalysts

Construction of hierarchical In2O3/In2S3-ZnCdS ternary microsphere heterostructures for efficient photocatalytic nitrogen fixation

Photocatalytic ammonia production holds immense promise as an environmentally sustainable approach to nitrogen fixation. In this study, In2O3/In2S3-ZnCdS ternary heterostructures were successfully constructed through an innovative in situ anion exchange process, coupled with a low-temperature hydrothermal method for ZnCdS (ZCS) incorporation. The resulting In2O3/In2S3-ZCS photocatalyst was proved to be highly efficient in converting N2 to NH3 under mild conditions, eliminating the need for sacrificial agents or precious metal catalysts. Notably, the NH4+ yield of In2O3/In2S3-0.5ZCS reached a significant level of 71.2 μmol g-1 h-1, which was 10.47 times higher than that of In2O3 (6.8 μmol g-1 h-1) and 3.22 times higher than that of In2O3/In2S3 (22.1 μmol g-1 h-1). This outstanding performance can be attributed to the ternary heterojunction configuration, which significantly extends the lifetime of photogenerated carriers and enhances the spatial separation of electrons and holes. The synergistic interplay between CdZnS, In2S3, and In2O3 in the heterojunction facilitates electron transport, thereby boosting the rate of the photocatalytic nitrogen fixation reaction. Our study not only validates the efficacy of ternary heterojunctions in photocatalytic nitrogen fixation but also offers valuable insights for the design and construction of such catalysts for future applications.

Modelling Photocatalytic N2 Reduction to Ammonia: Where We Stand and Where We Are Going

Artificial ammonia synthesis via the Haber-Bosch process is environmentally problematic due to the high energy consumption and corresponding CO2 ${_2 }$ emissions, produced during the reaction and before hand in hydrogen production upon methane steam reforming. Photocatalytic nitrogen fixation as a greener alternative to the conventional Haber-Bosch process enables us to perform nitrogen reduction reaction (NRR) under mild conditions, harnessing light as the energy source. Herein, we systematically review first-principles calculations used to determine the electronic/optical properties of photocatalysts, N2 adsorption and to expound possible NRR mechanisms. The most commonly studied photocatalysts for nitrogen fixation are usually modified with dopants, defects, co-catalysts and Z-scheme heterojunctions to prevent charge carrier recombination, improve charge separation efficiency and adjust a band gap to for utilizing a broader light spectrum. Most studies at the atomistic level of modeling are grounded upon density functional theory (DFT) calculations, wholly foregoing excitation effects paramount in photocatalysis. Hence, there is a dire need to consider methods beyond DFT to study the excited state properties more accurately. Furthermore, a few studies have been examined, which include higher level kinetics and macroscale simulations. Ultimately, we show there is still ample room for improvement with regard to first principles calculations and their integration in multiscale models.

Advances in the structural engineering of layered bismuth-based semiconductors for visible light-driven photocatalytic water splitting

Hydrogen production via the photocatalytic water splitting reaction on semiconductors presents a promising avenue to directly achieve solar energy conversion and storage. Bismuth-based semiconductors with layered structures, a hierarchical arrangement of components stacked in the form of two-dimensional extended layers where the atoms within each layer are typically strongly bonded, while the interactions between the layers are relatively weak, have emerged as an important series of photocatalyst candidates. In this review, we focus on the new emerging layered bismuth-based semiconductors with structures in Sillén, Aurivillius, Sillén-Aurivillius and bismuth chromate systems primarily employed in the photocatalytic water splitting reaction. From a crystal structure-oriented view, we delve into discussions on how the component and unit of a crystal structure influence the intrinsic properties, including light absorption and photogenerated charge transfer and separation, of materials as well as the corresponding photocatalytic performance of the water splitting reaction. The strategies for modulating the ferroelectricity and surface modification of these layered bismuth-based semiconductors are also involved. We also discuss the limitations of these materials accompanied by a forward-looking perspective, and we hope to provide some insights from the view of rational material design and engineering for the fabrication of high-efficiency photocatalytic water splitting systems.

Boosting photocatalytic nitrogen reduction reaction by Jahn-Teller effect

Compared with traditional the Haber-Bosch process, photocatalytic ammonia production has attracted a considerable attention due to its advantages of low energy consumption and sustainability. In this work, we mainly study the photocatalytic nitrogen reduction reaction (NRR) on MoO3·0.55H2O and α-MoO3. Structure analysis shows that compared to α-MoO6, the [MoO6] octahedrons in MoO3·0.55H2O obviously distort (Jahn-Teller distortion), leading to the formation of Lewis acid active sites that favors the adsorption and activation of N2. X-ray photoelectron spectroscopy (XPS) further confirms the formation of more Mo5+ as Lewis acid active sites in MoO3·0.55H2O. Transient photocurrent, photoluminescence and electrochemical impedance spectra (EIS) confirmed that MoO3·0.55H2O has a higher charge separation and transfer efficiency than α-MoO3. Density functional theory (DFT) calculation further confirmed that the N2 adsorption on MoO3·0.55H2O is more favorable thermodynamically than that on α-MoO3. As a result, under visible light irradiation (λ ≥ 400 nm) for 60 min, an ammonia production rate of 88.6 μmol·gcat-1 was achieved on MoO3·0.55H2O, which is about 4.6 times higher than that on α-MoO3. In comparison to other photocatalysts, MoO3·0.55H2O exhibits an excellent photocatalytic NRR activity under visible light irradiation without using sacrificial agent. This work offers a new fundamental understanding to photocatalytic NRR from the viewpoint of crystal fine structure, which benefits designing efficient photocatalysts.

Tailoring defects in SrTiO3 by one step nanoarchitectonics for realizing photocatalytic nitrogen fixation in pure water

Surface contamination of materials by nitrogenous impurities is a major problem that can bias the quantification of ammonia in photocatalytic N₂ fixation reactions. In this work, SrTiO₃ nanocubes were prepared by using a nitrogenous precursor and engineered with Ti³⁺ sites and oxygen vacancy defects in a one-step solvothermal approach. It was observed that the synthesized materials were containing surface nitrogenous impurities and therefore a rigorous cleaning procedure was adopted to eliminate them to the best extent. The contribution of unavoidable surface impurities was deduced in the form of adventitious NH₃ by employing control experiments and a realistic photocatalytic NH₃ generation was achieved. It was found that pristine SrTiO₃ showed no photocatalytic activity, whereas one of the defected SrTiO₃ materials showed the highest NH₃ formation under natural sunlight in pure water, which was ascribed to the tuned defect sites, enhanced surface area and efficient separation of photogenerated charges. Based on the experimental results, a stringent protocol has been suggested for materials synthesis while working with nitrogenous precursors and for subsequent photocatalytic N₂ fixation experiments. Thus, the present study provides a simple and affordable procedure for catalyst synthesis for the studied application and expands the scope of perovskite oxide materials to fabricate efficient photocatalysts for sustainable NH₃ production.

Tuned CuCr layered double hydroxide/carbon-based nanocomposites inducing sonophotocatalytic degradation of dimethyl phthalate

This study is the first to explore the possibility of utilizing CuCr LDH decorated on reduced graphene oxide (rGO) and graphene oxide (GO) as sonophotocatalysts for the degradation of dimethyl phthalate (DMP). CuCr LDH and its nanocomposites were successfully fabricated and characterized. Scanning electron microscopy (SEM) along with high-resolution transmission electron microscope (HRTEM) both evidenced the formation of randomly oriented nanosheet structures of CuCr LDH coupled with thin and folded sheets of GO and rGO. The impact of diverse processes on the degradation efficiency of DMP in the presence of the so-prepared catalysts was compared. Benefiting from the low bandgap and high specific surface area, the as-obtained CuCr LDH/rGO represented outstanding catalytic activity (100 %) toward 15 mg L-1 of DMP within 30 min when subjected to light and ultrasonic irradiations simultaneously. Radical quenching experiments and visual spectrophotometry using an O-phenylenediamine revealed the crucial role of hydroxyl radicals compared to holes and superoxide radicals. Overall, outcomes disclosed that CuCr LDH/rGO is a stable and proper sonophotocatalyst for environmental remediation.

Advances in Semiconductor-Based Nanocomposite Photo(electro)catalysts for Nitrogen Reduction to Ammonia

Photo(electro)catalytic nitrogen fixation technology is a promising ammonia synthesis technology using clean solar and electric energy as the driving energy. Abundant nitrogen and water as raw materials uphold the principle of green and sustainable development. However, the generally low efficiency of the nitrogen reduction reaction has seriously restricted the application and development of this technology. The paper introduces the nitrogen reduction process and discusses the main challenges and differences in the current photo(electro)catalytic nitrogen fixation systems. It focuses on promoting the adsorption and activation of N2 and the resolution and diffusion of NH3 generated. In recent years, reviews of the modification strategies of semiconductor materials in light of the typical cases of nitrogen fixation have been reported in the literature. Finally, the future development trend of this field is analyzed and prospected.

Dinitrogen Activation in the Gas Phase: Spectroscopic Characterization of C-N Coupling in the V3 C+ +N2 Reaction

We report on cluster-mediated C-N bond formation in the gas phase using N₂ as a nitrogen source. The V₃ C⁺ +N₂ reaction is studied by a combination of ion-trap mass spectrometry with infrared photodissociation (IRPD) spectroscopy and complemented by electronic structure calculations. The proposed reaction mechanism is spectroscopically validated by identifying the structures of the reactant and product ions. V₃ C⁺ exhibits a pyramidal structure of C₁ -symmetry. N₂ activation is initiated by adsorption in an end-on fashion at a vanadium site, followed by spontaneous cleavage of the N≡N triple bond and subsequent C-N coupling. The IRPD spectrum of the metal nitride product [NV₃ (C=N)]⁺ exhibits characteristic C=N double bond (1530 cm^-1 ) and V-N single bond (770, 541 and 522 cm^-1 ) stretching bands.

First-principles-driven catalyst design protocol of 2D/2D heterostructures for electro- and photocatalytic nitrogen reduction reaction

Ammonia synthesis from nitrogen is a vital process and a necessity in a variety of applications including energy, pharmaceutical, agricultural, and chemical applications. The electro- and photocatalytic nitrogen reduction reactions (NRRs) are promising sustainable processes operated under milder conditions than the conventional Haber-Bosch process. However, the main pain points of these catalytic processes are their low selectivity and low efficiency. This perspective presents the recent status and the design protocols for developing promising 2D/2D heterojunction catalysts for the NRR, using the first-principles approach. The current theoretical studies are briefly discussed, and available methods are suggested for the development and design of new potential 2D/2D heterojunctions as efficient electro- and photo-NRR catalysts.

Construction of Co3O4 nanopolyhedra with rich oxygen vacancies from ZIF-67 for efficient photocatalytic nitrogen fixation

Photocatalytic nitrogen fixation has attracted much attention due to the fact that it is a way of using solar energy to achieve clean and sustainable conversion of nitrogen to ammonia under mild conditions. In this paper, different proportions of Zn-doped Co₃O₄ nanopolyhedrons were synthesized using bimetallic ZIFs containing Co²⁺ and Zn²⁺ as precursors for the construction of photocatalytic nitrogen fixation semiconductor materials for the first time. The synthesized Co₃O₄ nano-polyhedron still retains the rhombic dodecahedron shape of ZIF-67 and exhibits a large specific surface area. Moreover, Zn doping results in abundant oxygen vacancies on the surface of Co₃O₄ polyhedron. These oxygen vacancies not only provide active sites for nitrogen adsorption and activation, but also enhance the separation ability of photocarriers, which can significantly improve the efficiency of photocatalytic nitrogen fixation of the material. When Zn-Co₃O₄-30 is utilized as the catalyst for photocatalytic nitrogen fixation, the nitrogen fixation rate is 96.8 μmol g^-1 h^-1, which is much higher than that of pure-Co₃O₄. In this study, heteroatom-doped Co₃O₄ polyhedron with rich oxygen vacancy was synthesized by low-temperature oxidation method, which provides a new idea for the design and synthesis of skeleton-based photocatalytic nitrogen fixation materials.

Photoinduced CO2 and N2 reductions on plasmonically enabled gallium oxide

Ag-containing ZnO/ β-Ga2O3 semiconductor, which exhibit reduced bandgap, increased light absorption, and hydrophilicity, have been found to be useful for photocatalytic CO2 reduction and N2 fixation by water. The charge-separation is facilitated by the new interfaces and inherent vacancies. The Ag@GaZn demonstrated the highest photocurrent response, about 20- and 2.27-folds that of the Ga and GaZn samples, respectively. CO, CH4, and H2 formed as products for photo-reduction of CO2. Ag@GaZn catalyst exhibited the highest AQY of 0.121 % at 400 nm (31.2 W/m2). Also, Ag@GaZn generated 740 μmolg-1 of NH4+ ions, which was about 18-folds higher than Ga sample. In situ DRIFTS for isotopic-labelled 13CO2 and 15N2 reaffirmed the photo-activity of as-synthesized catalysts. Density functional theory provided insight into the relative affinity of different planes of heterostructures towards H2O, CO2 and N2 molecules. The structure-photoactivity rationale behind the intriguing Ag@GaZn sample offers a fundamental insight into the role of plasmonic Ag and design principle of heterostructure with improved photoactivity and stability.

Construction of a 2D/2D g-C3N5/NiCr-LDH Heterostructure to Boost the Green Ammonia Production Rate under Visible Light Illumination

Photocatalytic N₂ fixation has emerged as one of the most useful ways to produce NH₃, a useful asset for chemical industries and a carbon-free energy source. Recently, significant progress has been made toward designing efficient photocatalysts to achieve this objective. Here, we introduce a highly active type-II heterojunction fabricated via integrating two-dimensional (2D) nanosheets of exfoliated g-C₃N₅ with nickel-chromium layered double hydroxide (NiCr-LDH). With an optimized loading of NiCr-LDH on exfoliated g-C₃N₅, excellent performance is realized for green ammonia synthesis under ambient conditions without any noble metal cocatalyst(s). Indeed, the g-C₃N₅/NiCr-LDH heterostructure with 2 wt % of NiCr-LDH (CN-NCL-2) exhibits an ammonia yield of about 2.523 mmol/g/h, which is about 7.51 and 2.86 times higher than that of solo catalysts, i.e., NiCr-LDH (NC-L) and exfoliated g-C₃N₅ (CN-5), respectively, where methanol is used as a sacrificial agent. The enhancement of NH₃ evolution by the g-C₃N₅/NiCr-LDH heterostructure can be attributed to the efficient charge transfer, a key factor to the photocatalytic N₂ fixation rate enhancement. Additionally, N₂ vacancies present in the system help adsorb N₂ on the surface, which improves the ammonia production rate further. The best-performing heterostructure also shows long-term stability with the NH₃ production rate remaining nearly constant over 20 h, demonstrating the excellent robustness of the photocatalyst.

MXenes as Emerging Materials: Synthesis, Properties, and Applications

Due to their unique layered microstructure, the presence of various functional groups at the surface, earth abundance, and attractive electrical, optical, and thermal properties, MXenes are considered promising candidates for the solution of energy- and environmental-related problems. It is seen that the energy conversion and storage capacity of MXenes can be enhanced by changing the material dimensions, chemical composition, structure, and surface chemistry. Hence, it is also essential to understand how one can easily improve the structure–property relationship from an applied point of view. In the current review, we reviewed the fabrication, properties, and potential applications of MXenes. In addition, various properties of MXenes such as structural, optical, electrical, thermal, chemical, and mechanical have been discussed. Furthermore, the potential applications of MXenes in the areas of photocatalysis, electrocatalysis, nitrogen fixation, gas sensing, cancer therapy, and supercapacitors have also been outlooked. Based on the reported works, it could easily be observed that the properties and applications of MXenes can be further enhanced by applying various modification and functionalization approaches. This review also emphasizes the recent developments and future perspectives of MXenes-based composite materials, which will greatly help scientists working in the fields of academia and material science.

Recent Advances in Application of Graphitic Carbon Nitride-Based Catalysts for Photocatalytic Nitrogen Fixation

Ammonia, the second most-produced chemical, is widely used in agricultural and industrial applications. However, traditional industrial ammonia production dominated by the Haber-Bosch process presents huge resource and environment issues due to the massive energy consumption and CO₂ emission. The newly emerged nitrogen fixation technology, photocatalytic N₂ reduction reaction (p-NRR), uses clean solar energy with zero-emission, holding great prospect to achieve sustainable ammonia synthesis. Although great efforts are made, the p-NRR catalysts still suffer from poor N₂ adsorption and activation, inferior light absorption, and fast recombination of photocarriers. Due to the tunable electronic structure of the metal-free polymeric graphitic carbon nitride (g-C₃ N₄ ), the above-mentioned issues can be significantly alleviated, making it the most promising p-NRR photocatalyst. This review summarizes the recent development of g-C₃ N₄ -based catalysts for p-NRR, including the working principle of p-NRR catalysts, the challenges of developing p-NRR catalysts, and corresponding solutions. Particularly, the roles of defect engineering and heterojunction construction on g-C₃ N₄ to the enhancement of photocatalytic performances are emphasized. In addition, computational studies are introduced to deepen the understanding of reaction pathways. At last, perspectives are provided on the development of p-NRR catalysts.

Assembling Lanthanide–Transition Metal Clusters on TiO2 for Photocatalytic Nitrogen Fixation

Ammonia synthesis using light with low energy consumption offers an effective solution for energy saving and environmental protection. Herein, an abundant oxygen vacancy photocatalyst was synthesized via the integration of...

Engineering of bionic Fe/Mo bimetallene for boosting the photocatalytic nitrogen reduction performance

The "FeMo cofactors" in biological nitrogenase play a decisive role in nitrogen reduction. Herein, a novel bionic Fe/Mo bimetallene was applied in photocatalytic nitrogen reduction. The surface coating Fe/Mo bimetallene of Bi₂Mo_0.3W_0.7O₆ (BMWO) nanocrystals could effectively promote the separation and transportation of photogenerated carriers by multi-electron redox reactions and deliver 2.8 times longer photo-carrier lifetime. Consequently, the nitrogen fixation activity of Fe/Mo bimetallene-coated BMWO nanocrystal photocatalyst was obviously enhanced (218.93 μmol g^-1h^-1), which was about 4.8 times that of unmodified BMWO nanocrystals. This work provides a novel approach to design bionic Fe/Mo bimetallene-modified inorganic semiconductor photocatalysts for nitrogen reduction.

Plasmon-enabled N2 photofixation on partially reduced Ti3C2 MXene

Benefiting from the superior conductivity, rich surface chemistry and tunable bandgap, Ti₃C₂ MXene has become a frontier cocatalyst material for boosting the efficiency of semiconductor photocatalysts. It has been theoretically predicted to be an ideal material for N₂ fixation. However, the realization of N₂ photofixation with Ti₃C₂ as a host photocatalyst has so far remained experimentally challenging. Herein, we report on a sandwich-like plasmon- and an MXene-based photocatalyst made of Au nanospheres and layered Ti₃C₂, and demonstrate its efficient N₂ photofixation in pure water under ambient conditions. The abundant low-valence Ti (Ti^(4-x)+) sites in partially reduced Ti₃C₂ (r-Ti₃C₂) produced by surface engineering through H₂ thermal reduction effectively capture and activate N₂, while Au nanospheres offer plasmonic hot electrons to reduce the activated N₂ into NH₃. The Ti^(4-x)+ active sites and plasmon-generated hot electrons work in tandem to endow r-Ti₃C₂/Au with remarkably enhanced N₂ photofixation activity. Importantly, r-Ti₃C₂/Au exhibits ultrahigh selectivity without the occurrence of competing H₂ evolution. This work opens up a promising route for the rational design of efficient MXene-based photocatalysts.

Atomically dispersed Palladium-Ethylene Glycol- Bismuth oxybromide for photocatalytic nitrogen fixation: Insight of molecular bridge mechanism

Performance of single-atom catalysis largely depends on the interaction between the metal and the supporter. Herein, ethylene glycol (EG) was used as a molecular bridge connecting Palladium (Pd) and bismuth oxybromide (BiOBr) to form atomically dispersed Pd catalyst (Pd-EG-BiOBr) for photocatalytic nitrogen fixation under ambient conditions. Compared with 0.20 wt% Pd-BiOBr, 0.20 wt% Pd-EG-BiOBr greatly promoted the photocatalytic nitrogen fixation activity, affording an ammonia formation rate of 124.63 μmol·h^-1. The molecular bridge mechanism during catalyst formation and photocatalysis is speculated based on Transmission electron microscopy, In-situ Fourier transform infrared spectra, Electron spin resonance spectra, UV-vis diffuse reflectance spectra, Photoluminescence spectra and Density Functional Theory calculations. The results show that EG not only induces the formation of atomically dispersed Pd, but also enhances the electron density of Pd and activation capacity of nitrogen molecules. This work opens a new door to applications of atomically dispersed Pd supported catalysts for high efficiency photocatalytic nitrogen fixation.

A review on vertical and lateral heterostructures of semiconducting 2D-MoS2 with other 2D materials: a feasible perspective for energy conversion

Fossil fuels as a double-edged sword are essential to daily life. However, the depletion of fossil fuel reservoirs has increased the search for alternative renewable energy sources to procure a more sustainable society. Accordingly, energy production through water splitting, CO₂ reduction and N₂ reduction via photocatalytic and electrocatalytic pathways is being contemplated as a greener methodology with zero environmental pollution. Owing to their atomic-level thickness, two-dimensional (2D) semiconductor catalysts have triggered the reawakening of interest in the field of energy and environmental applications. Among them, following the unconventional properties of graphene, 2D MoS₂ has been widely investigated due to its outstanding optical and electronic properties. However, the photo/electrocatalytic performance of 2D-MoS₂ is still unsatisfactory due to its low charge carrier density. Recently, the development of 2D/2D heterojunctions has evoked interdisciplinary research fascination in the scientific community, which can mitigate the shortcomings associated with 2D-MoS₂. Following the recent research trends, the present review covers the recent findings and key aspects on the synthetic methods, fundamental properties and practical applications of semiconducting 2D-MoS₂ and its heterostructures with other 2D materials such as g-C₃N₄, graphene, CdS, TiO₂, MXene, black phosphorous, and boron nitride. Besides, this review details the viable application of these materials in the area of hydrogen energy production via the H₂O splitting reaction, N₂ fixation to NH₃ formation and CO₂ reduction to different value-added hydrocarbons and alcohol products through both photocatalysis and electrocatalysis. The crucial role of the interface together with the charge separation principle between two individual 2D structures towards achieving satisfactory activity for various applications is presented. Overall, the current studies provide a snapshot of the recent breakthroughs in the development of various 2D/2D-based catalysts in the field of energy production, delivering opportunities for future research.

B and cyano groups co-doped g-C3N4 with multiple defects for photocatalytic nitrogen fixation in ultrapure water without hole scavengers

B atoms and cyano groups co-doped graphite carbon nitride with nitrogen vacancies (VN-BC-CN) was explored via one-step in-situ route. A series of comprehensive experiments confirmed that B atoms and cyano groups had been doped into the framework of graphite carbon nitride, forming VN-BC-CN catalyst sample with a large number of nitrogen-vacancy defects. As electron acceptors, B and cyano groups could be used as active sites for nitrogen conversion. The defect level caused by nitrogen vacancy led to red shift of the light absorption edge, which resulted in higher separation efficiency of photo-induced carriers and faster transfer rate of photo-induced electrons for the VN-BC-CN catalyst. This VN-BC-CN catalyst had good photocatalytic nitrogen fixation performance in the ultrapure water without any hole-scavengers. The nitrogen photofixation rate of VN-BC-CN (115.53 μmol g^-1 h^-1) was 25.5 times that of pure carbon nitride (GCN, 4.53 μmol g^-1 h^-1). Moreover, NH₄⁺ generation rate hardly decreased after 10 h reaction, and the NH₄⁺ generation rate could reach 79.56 μmol g^-1 h^-1 in the fifth cycle, showing the good photocatalytic stability of the VN-BC-CN catalyst.

Heterojunction photocatalysts for artificial nitrogen fixation: fundamentals, latest advances and future perspectives

As an indispensable energy source, ammonia plays an essential role in agriculture and various industries. Given that the current ammonia production is still dominated by the energy-intensive and high carbon footprint Haber-Bosch process, photocatalytic nitrogen fixation represents a low-energy consuming and sustainable approach to generate ammonia. Heterostructured photocatalysts are hybrid materials composed of semiconductor materials containing interfaces that make full use of the unique superiorities of the constituents and synergistic effects between them. These promising photocatalysts have superior performances and substantial potential in photocatalytic reduction of nitrogen. In this review, a wide spectrum of recently developed heterostructured photocatalysts for nitrogen fixation to ammonia are evaluated. The fundamentals of solar-to-ammonia conversion, basic principles of various heterojunction photocatalysts and modification strategies are systematically reviewed. Finally, a brief summary and perspectives on the ongoing challenges and directions for future development of nitrogen photofixation catalysts are also provided.

The application and improvement of TiO2 (titanate) based nanomaterials for the photoelectrochemical conversion of CO2 and N2 into useful products

In this review, we describe the photoelectrochemical (PEC) transformation of atmospheric species such as carbon dioxide (CO₂) and nitrogen (N₂) into useful industrial products on TiO₂ and TiO₂ composite photoelectrodes.

Surface structure-dependent photocatalytic O2 activation for pollutant removal with bismuth oxyhalides

The purification of water and air by semiconductor photocatalysis is a rapidly growing area for academic research and industrial innovation, featured with ambient removal of organic or inorganic pollutants by using solar light as the energy source and atmospheric O₂ as the green oxidant. Both charge transfer and energy transfer from excited photocatalysts can overcome the spin-forbidden nature of O₂. Layered bismuth oxyhalides are a new group of two-dimensional photocatalysts with an appealing geometric and surface structure that allows the dynamic and selective tuning of O₂ activation at the surface molecular level. In this Feature Article, we specifically summarize our recent progress in selective O₂ activation by engineering surface structures of bismuth oxyhalides. Then, we demonstrate selective photocatalytic O₂ activation of bismuth oxyhalides for environmental control, including water decontamination, volatile organic compound oxidation and nitrogen oxide removal, as well as selective catalytic oxidations. Challenges and opportunities regarding the design of photocatalysts with satisfactory performance for potential environmental control applications are also presented.

In situ preparation of g-C3N4 nanosheet/FeOCl: Achievement and promoted photocatalytic nitrogen fixation activity

Climate change, global warming, and population growth have led researchers to use eco-sociable procedures for the N₂ reduction reaction. It has discovered that N₂ molecule can be transformed into NH₃ in ambient circumstances with nanocomposites upon visible irradiation. In this research paper, a new visible-light-driven photocatalyst was constructed, with various weight percents of FeOCl particles (10, 20, 30, and 40%) that have adhered on NS-CN. Subsequently, multiple features of the nanocomposites were assayed in detail. The results illustrated that the NS-CN/FeOCl (20%) system has remarkable photoactivity in the NH₄⁺ production reaction in comparison with the NS-CN and CN, which showed 2.5 and 8.6 higher activity, respectively. The durability of NS-CN/FeOCl (20%) system, as a substantial factor, was assayed for 5 recycles. Moreover, the effect of electron quenchers, pH of media, and solvent was studied. At last, a feasible Z-scheme mechanism for the remarkable improvement of N₂ fixation efficiency was offered.

Modified Nano-TiO2 Based Composites for Environmental Photocatalytic Applications

TiO2 probably plays the most important role in photocatalysis due to its excellent chemical and physical properties. However, the band gap of TiO2 corresponds to the Ultraviolet (UV) region, which is inactive under visible irradiation. At present, TiO2 has become activated in the visible light region by metal and nonmetal doping and the fabrication of composites. Recently, nano-TiO2 has attracted much attention due to its characteristics of larger specific surface area and more exposed surface active sites. nano-TiO2 has been obtained in many morphologies such as ultrathin nanosheets, nanotubes, and hollow nanospheres. This work focuses on the application of nano-TiO2 in efficient environmental photocatalysis such as hydrogen production, dye degradation, CO2 degradation, and nitrogen fixation, and discusses the methods to improve the activity of nano-TiO2 in the future.

Single-atom transition metals supported on black phosphorene for electrochemical nitrogen reduction

The electrochemical nitrogen reduction reaction (NRR) is one of the most promising routes to produce ammonia under mild conditions. Black phosphorene (BP) has attracted wide attention as an NRR electrocatalyst owing to its high Fermi level and unique electronic structure. However, the low intrinsic activity of surface sites greatly restricts its application in the electrochemical NRR. In this work, we theoretically designed a series of single-atom transition metals anchored on the BP surface with MP3 (M = Fe, Mn, Cr, Mo, W, V and Nb) active sites for the NRR via density functional theory (DFT) calculations. By taking stability, activity and selectivity into consideration, the single-atom W-anchored BP was selected as a promising candidate for the NRR. The energy-favorable enzymatic pathway on W@BP (W atoms adsorb on the surface of BP) and the hybrid pathway on W-BP (W atoms substitute the surface P atoms of BP) have reaction onset potentials of 0.46 and 0.42 V, respectively, indicating that the single-atom W-anchored BP shows high activity towards the NRR. This high performance originates from the WP3 active sites, which act as an electron adaptor to activate N2 by donating electrons, thereby greatly regulating the charge transfer between BP and the reaction intermediates. This study proposes a promising active catalyst and provides theoretical guidance to construct BP-supported transition metal single-atom electrocatalysts for the NRR.

Surface-defect-engineered photocatalyst for nitrogen fixation into value-added chemical feedstocks

Surface-defect-engineered photocatalyst for nitrogen fixation.

2D MXene-derived Nb2O5/C/Nb2C/g-C3N4 heterojunctions for efficient nitrogen photofixation

Novel 2D MXene-derived Nb₂O₅/C/Nb₂C/g-C₃N₄ showed a high nitrogen reduction rate in water (0.365 mmol h⁻¹ g_cat⁻¹); the nitrogen reduction efficiency could be further promoted 2.5 times (0.927 mmol h⁻¹ g_cat⁻¹) with the optimized pH of 9.

An overview of photocatalysis facilitated by 2D heterojunctions

Two-dimensional (2D) photocatalysts have attracted considerable research interest in the past decades due to their unique optical, physical and chemical properties. Constructing 2D/2D heterojunctions with large interface area has been considered as an effective approach to enhance the transfer rate and the separation efficiency of the charge carriers, leading to dramatic increase in the photocatalytic performance of the photocatalysts. Here, the state-of-the-art progress on heterojunctions based on 2D materials is reviewed, including the photocatalysis principles using 2D heterojunctions, the categories of 2D heterojunctions and their application in different photocatalytic reactions, and the theoretical studies of the 2D heterojunctions. Moreover, the advantages and disadvantages of the 2D heterojunctions are also discussed. Finally, the ongoing challenges and opportunities for the future development of 2D photocatalysts with built-in heterojunctions are proposed.