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Description, Shearing flow induced spiral self-assembly of multi-shelled nanospheres with unusual chirality in block copolymer micelle system., Functional carbon nanospheres are exceptionally useful, yet controllable synthesis of them with well-defined porosity and complex multi-shelled nanostructure remains challenging. Here, we report a lamellar micelle spiral self-assembly strategy to synthesize multi-shelled mesoporous carbon nanospheres with unique chirality. This synthesis features the introduction of shearing flow to drive the spiral self-assembly, which is different from conventional chiral templating methods. Furthermore, a continuous adjustment in the amphipathicity of surfactants can cause the packing parameter changes, namely, micellar structure transformations, resulting in diverse pore structures from single-porous, to radial orientated, to flower-like, and to multi-shelled configurations. The self-supported spiral architecture of these multi-shelled carbon nanospheres, in combination with their high surface area (~530 m2 g−1), abundant nitrogen content (~6.2 weight %), and plentiful mesopores (~2.5 nm), affords them excellent electrochemical performance for potassium-ion storage. This simple but powerful micelle-directed self-assembly strategy offers inspiration for future nanostructure design of functional materials.

High capacity transition metal oxides have attracted much attention as potential sodium-ion batteries (SIBs) anodes. However, the fast capacity fading greatly limits their practical applications. In this study, highly crystallized mesoporous Fe3O4 nanoparticles encapsulated in the hollow nitrogen-doped carbon nanospheres (denoted as HCM-Fe3O4@void@N-C) have been synthesized and then explored as anode materials for SIBs. The resultant HCM-Fe3O4@void@N-C nanospheres possess a uniform particle size of ~ 180 nm with highly crystallized mesoporous Fe3O4 cores (~ 100 nm in diameter), a large surface area of ~ 250 m2 g−1 and a nitrogen-doped carbon shell (~ 7.6 wt%). Notably, a high discharge capacity of 372 mA h g−1 is obtained after the first five cycles at 160 mA g−1, which can gradually increase and be maintained at an ultrahigh specific capacity of 522 mA h g−1 even after 800 cycles. Besides, remarkable rate performance with a capacity of 196 mA h g−1 at a current density of 1200 mA g–1 and a high Coulombic efficiency (~ 100%) are obtained. Such good performance can be attributed to the unique yolk-shell nanostructure with a high crystallized mesoporous Fe3O4 core, a high conductive N-doped carbon shell, and a suitable void space, paving a new way to design and synthesize high-performance anode materials for SIBs.

Ultrafine nanoparticles with organic-inorganic hybridization have essential roles in myriad applications. Over the past three decades, although various efforts on the formation of organic or inorganic ultrasmall nanoparticles have been made, ultrafine organic-inorganic hybrid nanoparticles have scarcely been achieved. Herein, a family of ultrasmall hybrid nanoparticles with a monodisperse, uniform size is synthesized by a facile thermo-kinetics-mediated copolymer monomicelle approach. These thermo-kinetics-mediated monomicelles with amphiphilic ABC triblock copolymers are structurally robust due to their solidified polystyrene core, endowing them with ultrahigh thermodynamic stability, which is difficult to achieve using Pluronic surfactant-based micelles (e.g., F127). This great stability combined with a core-shell-corona structure makes the monodispersed monomicelles a robust template for the precise synthesis of ultrasmall hybrid nanoparticles with a highly uniform size. As a demonstration, the obtained micelles/SiO2 hybrid nanoparticles display ultrafine sizes, excellent uniformity, monodispersity, and tunable structural parameters (diameters: 24-47 nm and thin shell thickness: 2.0-4.0 nm). Notably, this approach is universal for creating a variety of multifunctional ultrasmall hybrid nanostructures, involving organic/organic micelle/polymers (polydopamine) nanoparticles, organic/inorganic micelle/metal oxides (ZnO, TiO2 , Fe2 O3 ), micelle/hydroxides (Co(OH)2 ), micelle/noble metals (Ag), and micelle/TiO2 /SiO2 hybrid composites. As a proof of concept, the ultrasmall micelle/SiO2 hybrid nanoparticles demonstrate superior toughness as biomimetic materials.

Mesoporous TiO2 nanomaterials have been investigated for decades; however, most endeavors have been focused on the exploration of their potentials in various applications, and the fundamental research for preparing mesoporous TiO2 in a highly controllable manner remains unfruitful. Herein, we report a facile pressure-driven oriented assembly approach to synthesize an unprecedented type of dehiscent mesoporous TiO2 microspheres with radial mesopore channels and oriented rutile crystallites. By varying the concentrated HCl amount, we have been able to produce TiO2 microspheres with well-controlled rutile/anatase phase ratio. By further manipulating the reaction conditions including solvent evaporation time and hydrothermal temperature, the oriented growth with tunable crevices can also be well manipulated. Such dehiscent mesoporous TiO2 microspheres have exhibited great permeability and excellent photocatalytic properties for H2 generation. We believe that the high structural complexity and predictability of this method offers great opportunities in enhancing the performance of TiO2-based materials. The development of porous materials and their applications has been in great demand recently. However, the progress in rational synthesis of porous semiconductors remains unproductive. Here, we have demonstrated a hydrothermal method to synthesize a novel type of mesoporous TiO2 microsphere with highly controllable structure. By regulating the synthetic conditions, the mesoporous TiO2 can be well controlled with oriented mesopores and lattices, tunable crystalline phase, and tailored open crevices. The resulting mesoporous TiO2 microspheres exhibit excellent penetration properties and photocatalytic activities, which is attributed to their unique mesostructures associated with accessible high surface area and particular architectures. Such a simple method, which is able to fabricate mesoporous TiO2 with controlled architectures and crystallites, is expected to be applied to produce numerous delicate nanostructures at moderate conditions for potential applications, such as catalysts, energy storage, and biosensors. We have demonstrated a facile hydrothermal approach to synthesize a novel type of mesoporous TiO2 material with highly controllable structure. By regulating the synthetic conditions, the mesoporous TiO2 can be well controlled with desired crystallites and architectures. The resulting mesoporous TiO2 exhibits excellent penetration properties and photocatalytic performance. These unique mesoporous TiO2 microspheres produced at moderate conditions could afford great opportunities in achieving high performance in various practical applications. The authors gratefully acknowledge funding support from the State Key Basic Research Program of China ( 2017YFA0207303 ), the National Science Foundation of China ( 21733003 ), Science and Technology Commission of Shanghai Municipality ( 17JC1400100 ), and Shanghai Leading Academic Discipline Project (B108). The authors extend their appreciation to the International Scientific Partnership Program ISPP at King Saud University for funding this research work through ISPP# 0018 . Scopus

Transition metal oxides (TMOs)/carbon nanocomposites are promising for high capacity long life lithium ion batteries (LIBs). Herein, we report a mesoporous carbon matrix confinement growth strategy to synthesize ultrasmall WO3 nanocrystals for lithium storage. In this strategy, WCl6 and phenolic resins (resol) are co-assembled with amphiphilic diblock copolymer PEO-b-PS into ordered mesostructures through an evaporation induced self-assembly (EISA) process. During the pyrolysis process, the resol molecules can be polymerized and carbonized into amorphous mesoporous carbon matrices, which lock the amorphous W species well. Then, WO3 nanocrystals are formed and are uniformly distributed in the ordered mesoporous carbon matrix with the increased pyrolysis temperature; moreover, the particle size is well controlled to ∼3 nm under the confinement effect of the carbon matrices. The resultant ordered mesoporous carbon/WO3 composites show very large pore size (∼11.3 nm), high surface area (∼157 m2 g−1), high pore volume (∼0.25 cm3 g−1), and WO3 content of 84%. As an anode material for LIBs, the obtained composites show excellent cycling stability and rate performance. A high specific capacity of 440 mA h g−1 can be achieved after 100 cycles at a current density of 0.1 A g−1. We believe that such a confinement synthesis strategy is versatile to create TMO-based nanocomposites for outstanding LIBs.

Ni-doped Bi2O3 (Ni–Bi2O3) microspheres have been synthesized by a one-pot solvothermal route. The morphology and structure of Ni–Bi2O3 microspheres can be well controlled by tailoring the preparative parameters (e.g., the content of Ni and reaction time). The resulted Ni–Bi2O3 microspheres are formed via a dissolution-recrystallization process resulting in mesoporous structure. Furthermore, when using as photocatalyst for removal of NO in air, it exhibits an enhanced performance in comparison with bare Bi2O3 under simulated solar light. First-principles calculations reveal that the enhanced activity of the catalyst could be attributed to the modification of geometric and electronic structure resulting from the dopant Ni. The present work could provide a new approach for synthesizing doped mesoporous Bi2O3 nanostructures with controlled morphology.

Graphitic carbon nitride (g-C3N4) with efficient photocatalytic activity was synthesized through thermal polymerization of thiourea with the addition of water (CN-W) or ethanol (CN-E) at 550 °C for 2 h. The physicochemical properties of the g-C3N4 were investigated by X-ray diffraction, transmission electron microscopy, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, diffuse-reflection spectroscopy, BET and BJH surface area characterization, and elemental analysis. The carbon content was found to have self-doped into the g-C3N4 matrix during the thermal polymerization of thiourea and ethanol. CN-W and CN-E showed considerably enhanced visible-light photocatalytic activity, with NO removal percentages of 37.2% and 48.3%, respectively. Compared with pure g-C3N4, both the short and long lifetimes of the charge carriers in CN-W and CN-E were found to be prolonged. The mechanism of improved visible-light photocatalytic activity was deduced. The present work may provide a facile route to optimize the microstructure of g-C3N4 photocatalysts for high-performance environmental and energy applications.

Semimetal bismuth with plasmonic properties has triggered increased interests. In this work, a facile strategy was developed to synthesize the Bi/(BiO)2CO3 (Bi-BOC) nanocomposites and Bi elemental photocatalysts. The Bi nanoparticles were produced via the insitu reduction of (BiO)2CO3 by NaBH4. The catalysts were utilized for the photocatalytic NO removal under visible light and UV illumination. Significantly, the photocatalytic capability of the Bi-BOC was highly enhanced with an unprecedented NO removal of 63.6%. The Bi metal demonstrated a direct plasmonic photocatalytic NO removal ratio of 53.6% under UV irradiation. The significantly enhanced photocatalytic capability of Bi-BOC can be ascribed to the synergistic effects of the SPR effect, enhanced visible-light-harvesting and the efficient electron–hole separation induced by Bi nanoparticles. The Bi nanoparticles can perform as a non-noble metal-based plasmonic cocatalyst for advancing photocatalytic ability. The mechanism of photocatalytic NO oxidation was proposed and compared under both visible light and UV illumination. Furthermore, the Bi-BOC photocatalysts showed good photochemical stability under repeated tests. This work could not only offer new insights into in-situ fine-tune reduction strategy for Bi-based photocatalysts, but also proves the potentials of utilizing low cost Bi cocatalysts as a substitute for noble metals to improve other photocatalysts.

An aqueous emulsion polymerization self‐assembly approach is demonstrated for the first time to synthesize ultrahigh nitrogen containing mesoporous polymer nanospheres, using melamine‐formaldehyde resin oligomers as precursors. In the synthesis, change from alkaline to acidic conditions is critical for the formation of monodisperse mesostructured polymer nanospheres. Owing to unique structure of triazine stabilized in the covalent polymeric networks during the pyrolysis process, the derived mesoporous carbon nanospheres possess an ultrahigh nitrogen content (up to 15.6 wt%) even after pyrolysis at 800 °C, which is the highest nitrogen content among mesoporous carbon nanospheres. Furthermore, these monodisperse mesoporous carbon nanospheres possess a high surface area (≈883 m2 g−1) and large pore size (≈8.1 nm). As an anode for sodium‐ion batteries, the ultrahigh nitrogen‐containing mesoporous carbon nanospheres exhibit superior rate capability (117 mAh g−1 at a high current density of 3 A g−1) and high reversible capacity (373 mAh g−1 at 0.06 A g−1), indicating a promising material for energy storage.

Semimetal bismuth (Bi) is an emerging non-noble metal-based plasmonic metal, which has demonstrated exceptional behavior as a unique plasmonic photocatalyst/cocatalyst. In the present work, Bi nanoparticles were uniformly deposited on the well-known TiO2 particles (Degussa, P25) with mixed phases of anatase and rutile by a facile eco-friendly synthesis at room temperature. The Bi-deposited TiO2 nanocomposites demonstrated highly enhanced photocatalytic performance for removal of ppb-level NO in air under visible-light irradiation (λ > 420 nm). The improved photocatalytic capability was found to be crucially dependent on the catalyst architecture: Bi nanoparticles with a diameter (dBi) of 5–8 nm deposited on the surface of TiO2 particles acted as active sites for visible-light-driven electron and hole separation. The enhanced charge separation was well supported by photoluminescence, photocurrent generation and Bode-phase spectra. Significantly, the exceptionally high visible-light photocatalytic capability of the optimized Bi–Ti-50 sample (the mass ratio of Bi to TiO2 is 50%) was also superior to that of universally known non-metal-doped TiO2. The photocatalysis was enhanced through SPR-mediated activation of the Bi particles by visible light followed by consecutive electron transfer in Bi/rutile/anatase interfaces, as supported by the action spectra. The electrons produced from the plasmonic activation of Bi particles could transfer to the conduction band of rutile and then to adjacent anatase TiO2 because of the high potential difference between Bi and rutile TiO2. Also, the free electrons could transfer from Bi to the conduction band of anatase and then to rutile TiO2 owing to the high mass ratio of anatase phase in P25 resulting in the direct contact of the Bi nanoparticles and anatase TiO2. A new photocatalysis mechanism of Bi-deposited TiO2 nanocomposites was proposed on the basis of active species trapping. The catalyst architecture elucidated here for promoted plasmonic photocatalysis would be beneficial for the design and development of more effective visible-light-driven photocatalysts for environmental remediation and could open a new avenue for utilization of low-cost Bi nanoparticles as a substitute for noble metals to promote the utilization efficiency of solar energy.

Highly ordered mesoporous γ-alumina microspheres with a shifted double-diamond mesostructure have been synthesized via a vesicle-aggregation-assembly approach., Alumina materials have widely been used in industrial fields, such as catalysis and adsorption. However, due to the fast sol–gel process and complicated crystalline-phase transformation, the synthesis of alumina materials with both highly ordered mesostructures and crystallized frameworks remains a great challenge. Herein, we report a novel vesicle-aggregation-assembly strategy to prepare highly ordered mesoporous γ-alumina microspheres with unique shifted double-diamond networks for the first time, by using diblock copolymer poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA) as a template and aluminum isopropoxide as a precursor in a tetrahydrofuran (THF)/hydrochloric acid binary solvent. During the gradual evaporation of THF and H2O, the as-made Al3+-based gel/PEO-b-PMMA composites can be obtained through a co-assembly process based on the hydrogen bonding interaction between hydroxyl groups of alumina oligomers and PEO segments of the diblock copolymers. The formed composites exhibit a spherical morphology with a wide size distribution (diameter size 1–12 μm). Furthermore, these composite microspheres possess an inverse bicontinuous cubic mesostructure (double diamond, Pn3[combining macron]m) with Al3+-based gel buried in the PEO-b-PMMA matrix in the form of two intertwined but disconnected networks. After a simple calcination at 900 °C in air, the structure of the resultant mesoporous alumina changes to a relatively low symmetry (shifted double diamond, Fd3[combining macron]m), ascribed to the shifting of the two alumina networks due to loss of the templates. Meanwhile, the unit cell size of the alumina mesostructure decreases from ∼131 to ∼95 nm. The obtained ordered mesoporous alumina products retain the spherical morphology and possess ultra-large mesopores (∼72.8 nm), columnar frameworks composed of γ-alumina nanocrystalline particles (crystal size of ∼15 nm) and high thermal stability (up to 900 °C). As a support of Au nanoparticles, the formed Au/mesoporous γ-alumina composite catalysts have been used in the catalytic reduction of 4-nitrophenol with a high kinetic constant k of 0.0888 min–1, implying promising potential as a catalyst support.

In order to fully address the low surface area, fast charge recombination and limited visible light absorption of pristine g-C3N4, we present a novel and straightforward strategy towards the synthesis of carbon self-doped g-C3N4 by using porous carbon foam as a soft-template. The C-doped g-C3N4 displayed a high BET surface area (65 m2 g−1), extended absorption ranging from visible light to near-infrared (800 nm) and accelerated electron–hole separation. The role of carbon doping on the band structure and electrical conductivity was revealed. The optimized C-doped g-C3N4 demonstrated an exceptionally high photocatalytic performance towards the purification of NO in air, and exceeded other reported visible-light photocatalysts, such as nonmetal-doped TiO2, BiOBr, (BiO)2CO3 and porous g-C3N4. This decent C-doped g-C3N4 photocatalyst also showed good photocatalytic stability for NO removal. The present work could provide new insights into the modification and understanding of self-doped semiconductor photocatalysts.

The development of approaches to effectively separate the photo-induced charge carriers is a key strategy to promote the photocatalytic activity of semiconductor photocatalysts. This work represents the construction of novel two-dimensional (2D) BiOBr/C3N4 nanojunctions by the growth of BiOBr nanosheets on the surface of C3N4 nanosheets at room temperature. The samples were characterized by XRD, FT-IR, TEM, UV-vis DRS and PL. The photocatalytic activity of the samples was evaluated by the removal of NO in air under visible light irradiation. The results indicated that electronic coupling took place between the {001} plane of BiOBr and {002} plane of C3N4. The BiOBr/C3N4 nanojunctions exhibited enhanced visible light photocatalytic activity compared with pure BiOBr and C3N4. The enhanced photoactivity can be mainly ascribed to the efficient separation and transportation of photo-induced electrons and holes due to the well-coupled crystal planes and well-matched band structures. The present work could provide new insights into the design and construction of 2D nanojunctions with well-matched crystal planes and band structures for efficient visible light photocatalysis.

The bismuth element synthesized by a facile chemical solution method exhibited an admirable and stable photocatalytic activity towards the removal of NO under 280 nm light irradiation due to the surface plasmon resonance mediated direct photocatalysis, and most strikingly, showed a catalytic "memory" capability following illumination.

To achieve efficient photocatalytic air purification, we constructed an advanced semimetal-organic Bi spheres-g-C3N4 nanohybrid through the in-situ growth of Bi nanospheres on g-C3N4 nanosheets. This Bi-g-C3N4 compound exhibited an exceptionally high and stable visible-light photocatalytic performance for NO removal due to the surface plasmon resonance (SPR) endowed by Bi metal. The SPR property of Bi could conspicuously enhance the visible-light harvesting and the charge separation. The electromagnetic field distribution of Bi spheres involving SPR effect was simulated and reaches its maximum in close proximity to the Bi particle surface. When the Bi metal content was controlled at 25%, the corresponding Bi-g-C3N4 displayed outstanding photocatalytic capability and transcended those of other visible-light photocatalysts. The Bi-g-C3N4 exhibited a high structural stability under repeated photocatalytic runs. A new visible-light-induced SPR-based photocatalysis mechanism with Bi-g-C3N4 was proposed on the basis of the DMPO-ESR spin-trapping. The photoinduced electrons could transfer from g-C3N4 to the Bi metal, as revealed with time-resolved fluorescence spectra. The function of Bi semimetal as a plasmonic cocatalyst for boosting visible light photocatalysis was similar to that of noble metals, which demonstrated a great potential of utilizing the economically feasible Bi element as a substitute for noble metals for the advancement of photocatalysis efficiency.

In the present work, it is very surprising to find that the precursors mass, a long overlooked factor for synthesis of 2D g-C3N4, exerts unexpected impact on g-C3N4 fabrication. The nanoarchitecture and photocatalytic capability of g-C3N4 can be well-tailored only by altering the precursors mass. As thiourea mass decreases, thin g-C3N4 nanosheets with higher surface area, elevated conduction band position and enhanced photocatalytic capability was triumphantly achieved. The optimized 2D g-C3N4 (CN-2T) exhibited exceptional high photocatalytic performance with a NO removal ratio of 48.3%, superior to that of BiOBr (21.3%), (BiO)2CO3 (18.6%) and Au/(BiO)2CO3 (33.8%). The excellent activity of CN-2T can be ascribed to the co-contribution of enlarged surface areas, strengthened electron-hole separation efficiency, enhanced electrons reduction capability and prolonged charge carriers lifetime. The DMPO ESR-spin trapping and hole trapping results demonstrate that the superoxide radicals (•O2−) and photogenerated holes are the main reactive species, while hydroxyl radicals (•OH) play a minor role in photocatalysis reaction. By monitoring the reaction intermediate and active species, the reaction mechanism for photocatalytic oxidation of NO by g-C3N4 was proposed. This strategy is novel and facile, which could stimulate numerous attentions in development of high-performance g-C3N4 based functional nanomaterials.

Semimetal bismuth (Bi), as an emerging non-noble metal-based cocatalyst and plasmonic photocatalyst, has attracted significant attention. In this work, a one-pot solvent-controlled synthesis strategy was utilized for the in situ-deposition of plasmonic Bi nanoparticles onto the surfaces of (BiO)2CO3 microspheres (BOC-WE) using bismuth citrate, sodium carbonate, and ethylene glycol as precursors. The introduction of the Bi nanoparticles has a pivotal effect on the morphology, optical and photocatalytic performance of the pristine (BiO)2CO3. The results indicated that the Bi nanoparticles were generated on the surface of (BiO)2CO3 microspheres via the in situ reduction of Bi(3+) by ethylene glycol. The Bi-deposited (BiO)2CO3 microspheres were used for the photocatalytic purification of NOx in air under visible light irradiation. Significantly, the BOC-WE samples exhibited a drastically promoted photocatalytic performance with a NOx removal ratio (η) of 37.2%, superior to pristine (BiO)2CO3 (η = 19.1%), outperforming other well-known visible light photocatalysts, such as C-doped TiO2 (η = 21.8%), BiOBr (η = 21.3%), BiOI (η = 14.9%) and C3N4 (η = 25.5%). The conspicuously enhanced photocatalytic capability can be attributed to the synergistic effects of the surface plasmon resonance (SPR) effect, increased visible light absorption and the efficient separation of electron-hole pairs induced by the Bi nanoparticles. The Bi nanoparticles can act as a non-noble metal-based cocatalyst for strengthening photocatalytic performance, which is similar to the behavior of noble metals (Au, Ag) in enhancing photocatalysis. The mechanism of visible light photocatalytic NOx oxidation was investigated. DMPO-ESR spin-trapping results demonstrated that hydroxyl radicals were confirmed to be the main active species for NOx photo-oxidation. Due to the SPR effect of Bi, the BOC-WE could produce more hydroxyl radicals than BOC, which was responsible for the enhanced NO photo-oxidation ability. Moreover, the BOC-WE photocatalysts showed high photochemical stability under repeated irradiation. This work demonstrates the feasibility of utilizing low cost Bi cocatalysts as a substitute for noble metals to enhance the performance of other photocatalysts. This work could not only provide new insights into the in situ fabrication of Bi/semiconductor nanocomposites, but also pave a new way for the modification of photocatalysts with non-noble metals as cocatalysts to achieve an enhanced performance for environmental and energetic applications.

Graphitic carbon nitride (g-C(3)N(4)), as an intriguing earth-abundant visible light photocatalyst, possesses a unique two-dimensional structure, excellent chemical stability and tunable electronic structure. Pure g-C(3)N(4) suffers from rapid recombination of photo-generated electron-hole pairs resulting in low photocatalytic activity. Because of the unique electronic structure, the g-C(3)N(4) could act as an eminent candidate for coupling with various functional materials to enhance the performance. According to the discrepancies in the photocatalytic mechanism and process, six primary systems of g-C(3)N(4)-based nanocomposites can be classified and summarized: namely, the g-C(3)N(4) based metal-free heterojunction, the g-C(3)N(4)/single metal oxide (metal sulfide) heterojunction, g-C(3)N(4)/composite oxide, the g-C(3)N(4)/halide heterojunction, g-C(3)N(4)/noble metal heterostructures, and the g-C(3)N(4) based complex system. Apart from the depiction of the fabrication methods, heterojunction structure and multifunctional application of the g-C(3)N(4)-based nanocomposites, we emphasize and elaborate on the underlying mechanisms in the photocatalytic activity enhancement of g-C(3)N(4)-based nanocomposites. The unique functions of the p-n junction (semiconductor/semiconductor heterostructures), the Schottky junction (metal/semiconductor heterostructures), the surface plasmon resonance (SPR) effect, photosensitization, superconductivity, etc. are utilized in the photocatalytic processes. Furthermore, the enhanced performance of g-C(3)N(4)-based nanocomposites has been widely employed in environmental and energetic applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation, carbon dioxide reduction, disinfection, and supercapacitors. This critical review ends with a summary and some perspectives on the challenges and new directions in exploring g-C(3)N(4)-based advanced nanomaterials.

The photocatalytic performance of the star photocatalyst g-C3N4 was restricted by the low efficiency because of the fast charge recombination. The present work developed a facile in situ method to construct g-C3N4/g-C3N4 metal-free isotype heterojunction with molecular composite precursors with the aim to greatly promote the charge separation. Considering the fact that g-C3N4 samples prepared from urea and thiourea separately have different band structure, the molecular composite precursors of urea and thiourea were treated simultaneously under the same thermal conditions, in situ creating a novel layered g-C3N4/g-C3N4 metal-free heterojunction (g-g CN heterojunction). This synthesis method is facile, economic, and environmentally benign using easily available earth-abundant green precursors. The confirmation of isotype g-g CN heterojunction was based on XRD, HRTEM, valence band XPS, ns-level PL, photocurrent, and EIS measurement. Upon visible-light irradiation, the photogenerated electrons transfer from g-C3N4 (thiourea) to g-C3N4 (urea) driven by the conduction band offset of 0.10 eV, whereas the photogenerated holes transfer from g-C3N4 (urea) to g-C3N4 (thiourea) driven by the valence band offset of 0.40 eV. The potential difference between the two g-C3N4 components in the heterojunction is the main driving force for efficient charge separation and transfer. For the removal of NO in air, the g-g CN heterojunction exhibited significantly enhanced visible light photocatalytic activity over g-C3N4 alone and physical mixture of g-C3N4 samples. The enhanced photocatalytic performance of g-g CN isotype heterojunction can be directly ascribed to efficient charge separation and transfer across the heterojunction interface as well as prolonged lifetime of charge carriers. This work demonstrated that rational design and construction of isotype heterojunction could open up a new avenue for the development of new efficient visible-light photocatalysts.

Three types of N-doped (BiO)2CO3 hierarchical microspheres composed of 2D nanosheets were fabricated by a one-pot template-free hydrothermal method from bismuth citrate and an ammonia solution under different hydrothermal temperatures. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and UV-visible diffuse reflectance spectroscopy. Here, the ammonia worked as a nitrogen resource, doping (BiO)2CO3, and a solvent hydrolyzing the bismuth citrate. The temperature was found to influence the thickness of the nanosheets and the morphology of the N-doped (BiO)2CO3 microspheres. The fascinating morphology of N-doped (BiO)2CO3, including rose-like, hydrangea flower-like and peony flower-like microspheres, can be controllably fabricated by adjusting the hydrothermal temperature. The photocatalytic activities of the as-prepared samples were evaluated towards the removal of NO under visible-light irradiation. Compared to pure (BiO)2CO3, the N-doped (BiO)2CO3 hierarchical microspheres showed enhanced photocatalytic activity. In addition, the hydrangea flower-like and the peony flower-like N-doped (BiO)2CO3 microspheres displayed admirable photocatalytic activity. Finally, a possible formation mechanism of the various morphologies of N-doped (BiO)2CO3 mediated by the reaction temperature was proposed. This work could provide new insights into the controlled synthesis of photocatalytic nano/microstructures for potential environmental applications.