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Topological morphology that dominates the surface electronic properties of nanostructures plays a key role in producing desired materials for versatile functions and applications in many fields, but its modulation for specific functions remains a big challenge. Herein, we report an acid-induced method to prepare S-doped graphitic carbon nitride/graphitic carbon nitride (S-CN/CN) homojunction by simply pyrolyzing a supramolecular precursor synthesized from melamine and H2SO4. The topological morphology and electronic structure of CN homojunction can be easily adjusted only by changing the ratio of raw materials. Moreover, the topological morphology of S-CN/CN homojunction can be further adjusted from hollow cocoon to 2D nanosheets by changing the annealing conditions. The optimized S-CN/CN homojunction shows highly efficient in charge transfer and separation and exhibits superior OER activity and high ability to degrade organic pollutants. Impressively, S-CN/CN nanosheets only demand low overpotential of 301 mV to drive a current density of 10 mAcm−2 in 1 M KOH media, and the corresponding Tafel slope is only 57.71 mV/dec, which is superior to the most advanced precious metal IrO2 catalyst. Moreover, under visible light irradiation, its photodegradation kinetic rate of RhB is 2.38, which is 47.6 times higher than that of bulk CN. This work provides useful guidance for designing and developing efficient multifunctional metal-free catalysts.

Graphitic carbon nitride quantum dots (CNQDs) are emerging as attractive photoluminescent (PL) materials with excellent application potential in fluorescence imaging and heavy-metal ion detection. However, three limitations, namely, low quantum yields (QYs), self-quenching, and excitation-dependent PL emission behaviors, severely impede the commercial applications of crystalline CNQDs. Here we address these three challenges by synthesizing boron-doped amorphous CNQDs via a hydrothermal process followed by the top-down cutting approach. Structural disorder endows the amorphous boron-doped CNQDs (B-CNQDs) with superior elastic strain performance over a wide range of pH values, thus effectively promoting mass transport and reducing exciton quenching. Boron as a dopant could fine-tune the electronic structure and emission properties of the PL material to achieve excitation-independent emission via the formation of uniform boron states. As a result, the amorphous B-CNQDs show unprecedented fluorescent stability (i.e., no obvious fading after two years) and a high QY of 87.4%; these values indicate that the quantum dots obtained are very promising fluorescent materials. Moreover, the B-CNQDs show bright-blue fluorescence under ultraviolet excitation when applied as ink on commercially available paper and are capable of the selective and sensitive detection of Fe2+ and Cd2+ in the parts-per-billion range. This work presents a novel avenue and scientific insights on amorphous carbon-based fluorescent materials for photoelectrical devices and sensors.

AIMS To evaluate the effectiveness of the hospital-family holistic care model based on the theory of 'Timing It Right' in caregivers of patients with permanent enterostomy. DESIGN A prospective randomized controlled trial. METHODS One hundred and twenty-five caregivers of patients with permanent enterostomy were recruited from 1 May 2017-31 August 2019. They were randomized into either intervention group (N = 62) or control group (N = 63). The control group received routine care and follow-up, while the intervention group received routine care, follow-up, and hospital-family holistic care intervention based on 'Timing It Right'. The care ability, psychological distress, and life quality of the caregivers were evaluated between the groups before the intervention, at discharge, and 3 and 6 months after discharge. RESULTS One hundred and eleven caregivers completed the study (88.8%). At 3 and 6 months after discharge, the care ability and life quality in the intervention group were significantly better than those in the control group (t = 8.506/9.783, t = 22.652/26.179, p

Structural symmetry-breaking that could lead to exotic physical properties plays a crucial role in determining the functions of a system, especially for two-dimensional (2D) materials. Here we demonstrate that multiple functionalities of 2D chromium-based materials could be achieved by breaking inversion symmetry via replacing Y atoms in one face of pristine CrY (Y=P, As, Sb) monolayers with N atoms, i.e., forming Janus Cr2NY monolayers. The functionalities include spin-gapless, very low work function, inducing carrier doping and catalytic activity, which are predominately ascribed to the large intrinsic dipole of Janus Cr2NY monolayers, making them having great potentials in various applications. Specifically, Cr2NSb is found to be a spin-gapless semiconductor, Cr2NP and Cr2NHPF could simultaneously induce n- and p-type carrier doping for two graphene sheets with different concentrations (forming intrinsic p-n vertical junction), and Cr2NY exhibits excellent electrocatalytic hydrogen evolution activity, even superior to benchmark Pt. The results confirm that breaking symmetry is a promising approach for the rational design of multifunctional 2D materials.

Steering charge kinetics at the interface is essential to improve the photocatalytic performance of two-dimensional (2D) material-based heterostructures. Herein, we developed a novel strategy–simultaneously building two kinds of heterojunctions– to modulate interfacial charge kinetics in polymeric carbon nitride (CN) for improving the photocatalytic activity. Using a simple one-step thermal condensation of carbon quantum dot (CQD)-contained supramolecular precursors formed in water, the controllable CQD embedded CN nanoframes possessed two kinds of heterogeneous interfaces within seamlessly stitched micro-area two-dimensional in-plane and out-of-plane domains. These two kinds of heterojunctions can effectively enhance its intrinsic driving force to accelerate the separation and transfer of charge along different directions. Furthermore, the hollow double-deck porous CN-CQD nanoframes with a high surface area (296.74 m2 g−1) endowed more exposed active sites. The remarkable visible-light photocatalytic activity of hollow porous CN-CQD nanoframes was demonstrated by degrading tetracycline (TC) and rhodamine (RhB) as the models, whose robust degradation rate constant is approximately 11 and 29 times higher than that of pristine CN, respectively. This work provides a novel strategy for the interfacial design of the heterophase junction with atomic precision.

Geometric dimensionality and morphology largely affect the properties and functionalities of materials; however, simultaneously regulating them to realize synergic effects is a formidable scientific and technological challenge. Here we demonstrate an effective strategy to control the dimensionality and morphology of graphitic carbon nitride (g-C3N4) through heat treatment the melamine-cyanuric acid supramolecular precursors formed in water as a “green” solvent. By varying heat treatments, the three-dimensional (3D) hexagonal prism precursors could be transformed to 3D g-C3N4 loofah-like (CNl) architectures, ultrathin two-dimensional (2D) g-C3N4 nanosheets (CNs), and ordered one-dimensional (1D) g-C3N4 nanotube (CNt) array, respectively. The adsorbed melamine molecules on the surface of precursor and atmosphere in the transformation process, play a key role in determining the morphology of products. The resulting ultrathin 2D CNs have a porous structure, a small thickness (1.6 nm), a large surface area (208.8 m2·g−1), and high conductivity, thus exhibiting higher hydrogen evolution rate (23.9 μmol h−1) by 17.3 times than the bulk g-C3N4 (CN) under visible light irradiation. This strategy results in high-quality, ultrathin CNs at yields of ∼10 wt% from raw material, much higher than those of previous reports (∼6 wt% from bulk CN). This work not only enriches our understanding of the relationship between geometric dimensionality, morphology and properties of photocatalytic nanomaterials, but also could be potentially useful for the design and growth of 1D or 2D flexible polymers for energy-related applications and beyond.

Rationally engineering the microstructure and electronic structure of catalysts to induce high activity for versatile applications remains a challenge. Herein, chlorine doped graphitic carbon nitride (Cl-doped g-C3N4) nanorings have been designed as a superior photocatalyst for pollutant degradation and oxygen evolution reaction (OER). Remarkably, Cl-doped g-C3N4 nanorings display enhanced OER performance with a small overpotential of approximately 290 mV at current density of 10 mA cm−2 and Tafel slope of 83 mV dec-1, possessing comparable OER activity to precious metal oxides RuO2 and IrO2/C. The excellent catalytic performance of Cl-doped g-C3N4 nanorings originates from the strong oxidation capability, abundant active sites exposed and efficient charge transfer. More importantly, visible light irradiation gives rise to a prominent improvement of the OER performance, reducing the OER overpotential and Tafel slope by 140 mV and 28 mV dec-1, respectively, demonstrating the striking photo-responsive OER activity of Cl-doped g-C3N4 nanorings. The great photo-induced improvement in OER activity would be related to the efficient charge transfer and the OH radicals arising spontaneously on CN-Cl100 catalyst upon light irradiation. This work establishes Cl-doped g-C3N4 nanorings as a highly competitive metal-free candidate for photoelectrochemical energy conversion and environmental cleaning application.

Both structural topology and composition strongly affect material properties and functionality, however, controlling both of them to achieve their synergic effects has been a long-sought goal. One-dimensional (1D) hollow structures have fantastic architectures and tunable physicochemical properties, but constructing them with desirable interiors and composition is extremely challenging. Here we report a facile and scalable approach, based on molecular self-assembly in water, for synthesizing hollow BCN microrods with hierarchical multichannel structure. The structural topology and composition of 1D hollow BCN are found to be easily tuned only by varying the annealing temperature. The multilevel interior structure and tunable composition make hollow BCN a multifunctional material, demonstrated by its impressive OER activity, high removal ability for heavy metals and organic pollutant. Specifically, its overpotential at a current density of 10 mAcm−2 is about 350 mV, outperforming the state-of-the-art precious-metal IrO2 catalyst, and its adsorption capacity for Cu2+ reaches up to a staggering 962.9 mg/g due to the synergistic effects of structural topology and composition. Our study provides an exceptionally simple strategy to tailor the structural topology and composition of materials, which are attractive for many applications.

The proton transfer plays a crucial, yet not well-control, role in enhancing the oxygen evolution reaction (OER) performance of transition metal (TM) (oxy) hydroxide materials. Herein, we take Ce-doped FeCo layered double hydroxide (Ce-FeCo LDH) nanosheets in situ growth on spindle-like MIL-88A, as a model system to demonstrate enhancing OER activity through the promotion of proton transfer by forming the carboxylate ligands coordinated with TM atoms. The carboxyl group-functionalized MIL-88A@Ce-FeCo LDH core–shell hybrid catalyst, fabricated by the one-pot reflux method, is made up of Ce-FeCo LDH as active component and carboxylate ligands as a proton acceptor. Specifically, the uncoordinated carboxylate ligands serve as relays to promote proton transfer and deprotonation efficiency. As a result, this core–shell structured hybrid exhibits superior OER activity while maintaining excellent durability. This work provides a facile method to reserve carboxylates as the station of proton transfer on TM-based catalyst to promote water splitting.

The exploration of earth-abundant electrocatalysts and insight on the relationship between their activity and structure is challenging for large-scale electrochemical water oxidation. Herein, 2D Co-Cu-P nanosheets on Ni foam are fabricated by electrodeposition and subsequent phosphorization process. The Co-Cu-P nanosheets are highly interconnected to form an open-structured hierarchical network structure, which endows the product large surface area, efficient mass transportation, and fast gas releasing. In addition, the surface of Co-Cu-P would rapidly convert into hydroxides layer in the earlier oxygen evolution reaction (OER) process, which preserves the Co-Cu-P phosphide inside and serves as the real active sites for OER process. Benefiting from the rationally designed open-structured hierarchical network and the synergistic effect from the two kinds of metal cations with high conductivity, the resultant Co-Cu-P bimetal phosphide open-structured network delivers superb OER performance with an overpotential of 240 mV to drive a current density of 10 mA cm−2 in alkaline medium, outperforming the performance of the Co-P and Cu3P monometallic phosphide counterpart. This work provides a simple synthesis approach to construct bimetal phosphide with a rationally designed open-structured hierarchical network toward boosting electrocatalytic OER performance. The open-structured hierarchical Co-Cu-P/NF network would serve as a robust catalyst for electrochemical water oxidation. The remarkable OER electrocatalytic performance of Co-Cu-P/NF can be mainly attributed to the large surface area, efficient mass transportation and fast gas releasing, as well as the metallic character of Co-Cu-P/NF with a high conductivity.

Polymeric graphitic carbon nitride (g-C3N4) materials are promising catalysts to compete with precious metals, but they mostly only show moderate catalytic activity, particularly low oxidation power for oxygen evolution reaction (OER). Although activating strategies, such as nanostructure designing and band structure engineering, have led to remarkable activity gains, there remains considerable room to improve performance that aims for real applications. We report here a novel strategy—protonating supramolecular aggregates followed by thermal polycondensation—to prepare porous g-C3N4 nanosheets (SH-g-C3N4) with high oxidation power, which employ as bifunctional OER catalyst and highly efficient photocatalyst material. The OER onset potentials of 1.47 V and Tafel slope of 128 mV dec−1 over SH-g-C3N4 are superior to the g-C3N4 obtained from supramolecular aggregates without protonation (S-g-C3N4). Furthermore, its Tafel slope would be reduced to 63.6 mV dec−1 under visible light irradiation, which is comparable to that of the active commercial RuO2 and IrO2 catalysts. Interestingly, the achieved nanosheets display enhanced visible light photocatalytic activity. The striking catalysis performance of SH-g-C3N4 can be ascribed to the unique advantage of its highly porous structure and favorable electronic structure and the generation of lots of ·O 2 − and ·OH radicals promoting the kinetic process. Our theoretical calculations reveal the mechanism of photoelectric catalyst for oxygen evolution reaction. This work provides a facile and scalable method to design highly efficient polymeric catalysts.

The development of highly active photocatalysts is the primary goal in the field of photocatalysis. We herein first develop a facile and scale up approach to synthesize porous polymeric graphitic carbon nitride (g-C3N4) with lamellar structure through thermal polycondensation of supramolecular aggregates. The feature of this approach lies in the directed in-situ self-assembly of cyanuric acid molecules, converted from the hydrolysis of melamine in NaOH solution, with the residual melamine molecules to form supramolecular aggregates, which lead to the formation of porous g-C3N4 with lamellar structure. The synthesized lamellar g-C3N4 exhibit superior photocatalytic activity as demonstrated by the complete degradation of methylene blue (MB) under one hour’s visible light irradiation, as well as excellent stability with high activity retained after four runs of MB degradation testing. The enhancement in photocatalytic performance can be attributed to its unique lamellar structure with high surface area, narrow bandgap, and efficient separation of photogenerated electron-hole pairs. This work shows that the alkaline solutions can be used as the molecular self-assembly medium and opens a new avenue towards designing highly active g-C3N4-based photocatalyts for energy and environmental applications.

Efficient spatial charge separation and transfer that are critical factors for solar energy conversion primarily depend on the energetic alignment of the band edges at interfaces in heterojunctions. Herein, we first report that constructing a 0D/0D type-II(T-II)/T-II heterojunction is an effective strategy to ingeniously achieve long-range charge separation by taking a ternary heterojunction of TiO2 and graphitic carbon nitride (g-C3N4) as a proof-of-concept. Incorporating g-C3N4 quantum dots (QCN), as the third component, into the commercial P25 composed of anatase (a-TiO2) and rutile (r-TiO2) can be realized via simply mixing the commercially available Degussa P25 and QCN solution followed by heat treatment. The strong coupling and matching band structures among a-TiO2, r-TiO2 and QCN result in the construction of novel T-II/T-II heterojunctions, which would promote the spatial separation and transfer of photogenerated electrons and holes. Moreover, QCN plays a key role in reinforcing light absorption. Particularly, the unique 0D/0D architecture possesses the advantages of abundant active sites for the photocatalytic reaction. As a result, the optimized QCN/a-TiO2/r-TiO2 heterojunctions exhibit enhanced photocatalytic H2 and O2 evolution, especially the hydrogen evolution rate (49.3 μmol h-1) is 11.7 times that of bare P25 under visible light irradiation, and sufficient catalytic stability as evidenced by the recycling experiments. The remarkably enhanced photocatalytic activity can be attributed to the synergistic effects of the energy level alignment at interfaces, the dimensionality and component of the heterojunctions. This work provides a stepping stone towards the design of novel heterojunctions for photocatalytic water splitting.

As a low-cost visible-light-driven metal-free catalyst, graphitic carbon nitride (g-C 3 N 4 ) has attracted increasing attention due to its wide applications for solar energy conversion, environmental purification, and organic photosynthesis. In particular, the catalytic performance of g-C 3 N 4 can be easily modulated by modifying morphology, doping, and copolymerization. Simultaneous optimization, however, has little been achieved. Herein, a facile one-pot strategy is developed to synthesize porous B-doped g-C 3 N 4 nanosheets by using H 3 BO 3 and urea as the precursor during thermal polymerization. The resultant B-doped g-C 3 N 4 nanosheets retain the original framework of bulk g-C 3 N 4 , while induce prominently enhanced visible light harvesting and narrowing band gap by 0.32 eV compared to pure g-C 3 N 4 . Moreover, the adsorption capacity and photodegradation kinetics of methylene blue (MB) under visible light irradiation over B-doped g-C 3 N 4 nanosheets can be improved by 20.5 and 17 times, respectively. The synthesized porous B-doped g-C 3 N 4 nanosheets also exhibit higher activities than pure g-C 3 N 4 as bifunctional electrocatalyst for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The enhanced catalyst performance of porous B-doped g-C 3 N 4 nanosheets stems from the strong synergistic effect originating from the larger exposed active sites generated by the exfoliation of g-C 3 N 4 into nanosheets and the porous structure, as well as the better conductivity owing to B-doping. This work provides a simple, effective, and robust method for the synthesis of g-C 3 N 4 -based nanomaterial with superior properties to meet the needs of various applications.

The utilization efficiency of hot carriers in photocatalyst is limited at present by their fast recombination. Heterojunction interface would reduce the recombination rate by effectively facilitati...

Tuning electron transfer at interface, largely depending upon interfacial interaction, is paramount to rationally designing nanoscale heterostructures with desirable performance for future electronics, optoelectronics, and solar energy conversion. Here, we explore the interfacial interaction between monolayer MoS2 and TiO2 cluster to elucidate the mechanism of the enhanced photocatalytic activity of their hybrids. It is firstly revealed that both dispersive (van der Waals forces) and covalent interactions can simultaneously exist in the monolayer MoS2/TiO2 cluster heterostructures, which depends on their relative orientations. The Ti-S and O=S bonds in covalently bonded heterostructures and flat bands in noncovalent heterostructures lead to an effective separation of photoexcited charge carriers between two constituents, therefore enhanced photocatalytic activity. The small band gap enables the MoS2/TiO2 cluster heterostructures having strong optical absorption in the whole visible light. Moreover, the Mo and S atoms at basal plane, which are catalytically inert, turn into catalytic active sites, making the monolayer MoS2 to be a highly active co-catalyst. These findings disclose the elusive microscopic mechanism behind the enhanced photocatalytic activity of MoS2/TiO2 hybrids, and provide a systematic step towards a better understanding of interfacial interaction in layered MoS2-based heterostructures.

Constructing all-solid-state Z-scheme junction is a very effective strategy to design highly active photocatalysts for solar energy conversion and environmental purification. We herein firstly construct 2D g-C3N4/g-C3N4 Z-scheme homojunction by using a bottom-up approach, during which the supramolecular complex is initially formed, followed by a facile thermal polycondensation. Based on the active species trapping experiments, Mott–Schottky test and band edge position analysis, the prepared 2D nanosheet g-C3N4/g-C3N4 homojunctions are found to be Z-scheme type, different from those available reported ones with a type-II energy alignment. Benefiting from the specific 2D morphology with large exposed surface area and Z-scheme junction with efficient separation and high redox abilities of the photoinduced electrons and holes, the obtained 2D g-C3N4/g-C3N4 homojunctions are much more active than the conventional g-C3N4/g-C3N4 homojunction (CN-MT) and bulk g-C3N4 (CN-M) under visible light irradiation, validating by the high rhodamine degradation rate of 0.833 h−1, which is about 3.9 and 15.4 times higher than that of CN-MT (0.214 h−1) and CN-M (0.054 h−1), respectively. The present work sheds light on design of novel Z-scheme photocatalysts with specific morphology and thus further application in the field of environment or energy.

Elimination of pollutants from water is one of the greatest challenges in resolving global environmental issues. Herein, we report a high-surface-area mesoporous g-C3N4 nanosheet with remarkable high adsorption capacity and photocatalytic performance, which is prepared through directly polycondensation of urea followed by a consecutive one-step thermal exfoliation strategy. This one-pot method to prepare mesoporous g-C3N4 nanosheet is facile and rapid in comparison with others. The superior adsorption capacity of the fabricated mesoporous g-C3N4 nanostructures is demonstrated by a model organic pollutant-methylene blue (MB), which is up to 72.2 mg/g, about 6 times as that of the largest value of various g-C3N4 adsorbents reported so far. Moreover, this kind of porous g-C3N4 nanosheet exhibits high photocatalytic activity to MB and phenol degradation. Particularly, the regenerated samples show excellent performance of pollutant removal after consecutive adsorption/degradation cycles. Therefore, this mesoporous g-C3N4 nanosheet may be an attractive robust metal-free material with great promise for organic pollutant elimination.

Converting solar energy into renewable clean fuels of hydrogen via photocatalytic water splitting provides the most prospective strategy for tackling the energy and environmental issues. The performance of most photocatalysts is closely related to the intrinsic activity and active edge sites; however, simultaneously regulating them to realize synergic effects remains significant scientific and technological challenge. Here, we report an elaborate design and synthesis of porous carbon nitride nanocages (CN-C) with abundant π-electron densities by a novel host–guest supramolecular self-assembly strategy, overcoming one of the major challenges of traditional copolymeration method, i.e., the required highly matched chemical structure and physical properties of the π-electron-rich monomers to nitrogen-rich monomers. This strategy primarily depends on the cooperation of the host supramolecular precursor growth and the self-regulation of guest supermolecules to compensate the inherent shortage of each component. Interestingly, the structural topology and electron densities of CN-C are found to be easily modulated by only varying the amount of urea. Benefiting from the synergic effects of hierarchically porous structures with enriched active sites and excellent accessibility, increased abundant π-electron densities and improved visible-light absorption, the CN-C nanocages exhibit remarkable photocatalytic hydrogen evolution activity under visible light exposure with H2 generation rate of 1135 μmol h−1g−1, which is 19 times higher than that of pristine CN (59.8 μmol h−1g−1). This powerful strategy provides a profound molecular-level insight into the control of morphology and π-electron densities within carbon-based materials.

Silicene has shown great application potential as a versatile material for nanoelectronics, particularly promising as building block for spintronic applications. Unfortunately, despite its intriguing properties, such as relatively large spin-orbit interactions, one of the biggest hurdles for silicene to be useful as a host spintronic material is the lack of magnetism or the topological phase transition owing to the silicene-substrate interactions, which influence its fundamental properties and has yet to be fully explored. Here, we show that when silicene is grown on CeO2 substrate, an appreciable robust magnetic moment appears in silicene covalently bonded to CeO2 (111), while a topological phase transition to a band insulator occurs regardless of van der Waals (vdWs) interaction or covalent bonding interaction at interface. The induced magnetism of silicene is due to the breaking of Si-Si {\pi}-bonding, also resulting in trivial topological phase. The silicene-substrate interaction, even weak vdWs force (equivalent to an electric field), can destroy quantum spin Hall effect (QSHE) of silicene. We propose a viable strategy --- constructing inverse symmetrical sandwich structure (protective layer/silicene/substrate) --- to preserve quantum spin Hall (QSH) state of silicene in weak vdWs interaction system. This work takes a critical step towards fundamental physics and realistic applications of silicene-based spintronic devices., Comment: 28 pages, 7 figures, and Supporting Information. arXiv admin note: substantial text overlap with arXiv:1802.00591

Platinum-chalcogen compounds such as platinum dichalcogenides (e.g., PtS2 and PtTe2) have been explored in an effort to study their potential applications in different fields to reduce the use of precious Pt. Herein, the adsorption of NO2, NO, NH3, H2O, CO2, CO and CH4 on monolayer PtTe2 is investigated by using first-principles calculations to exploit its potential applications as gas sensor. Among these gas molecules, only NO2 molecule could be adsorbed on PtTe2 with suitable adsorption strength and apparent charge transfer of 0.4506 e. We further calculate the current-voltage (I–V) relation using the nonequilibrium Green's function (NEGF) method. The transport feature exhibits distinct responses with a dramatic change of I–V relation before and after NO 2 adsorption on monolayer PtTe2: an obvious increase of 259 % in current after NO2 adsorption when the applied voltage is 0.98 V. The findings suggest that monolayer PtTe2 is a promising candidate for the NO2 molecule sensor with high selectivity and sensitivity.

A high light-absorption coefficient and long-range hot-carrier transport of hybrid organic-inorganic perovskites give huge potential to their composites in solar energy conversion and environmental protection. Understanding interfacial interactions and their effects are paramount for designing perovskite-based heterostructures with desirable properties. Herein, we systematically investigated the interfacial interactions in monolayer and few-layer SnS/CH3 NH3 PbI3 heterostructures and their effects on the electronic and optical properties of these structures by density functional theory. It was found that the interfacial interactions in SnS/CH3 NH3 PbI3 heterostructures were van der Waals (vdW) interactions, and they were found to be insensitive to the layer number of 2D SnS sheets. Interestingly, although their band gap decreased upon increasing the layer number of SnS, the near-gap electronic states and optical absorption spectra of these heterostructures were found to be strikingly similar. This feature was determined to be critical for the design of 2D layered SnS-based heterostructures. Strong absorption in the ultraviolet and visible-light regions, type II staggered band alignment at the interface, and few-layer SnS as an active co-catalyst make 2D SnS/CH3 NH3 PbI3 heterostructures promising candidates for photocatalysis, photodetectors, and solar energy harvesting and conversion. These results provide first insight into the nature of interfacial interactions and are useful for designing hybrid organic-inorganic perovskite-based devices with novel properties.

Carbon nanomaterials are prominent building blocks in the synthetic van der Waals (vdW) heterostructures with desired properties. Scientific understanding of their interfacial interactions is the premise to design this kind of vdW heterostructures with optimal performance. We here study the mechanism of enhanced photocatalytic activity of SnO 2 by fullerene modification at electronic level, to explore the interfacial interaction and its correlation with photocatalytic activity. The results show that the interfacial interaction increases with the number of C atom of fullerene, and leads to some of C atoms be positively/negatively charged, making the fullerene a highly active co-catalyst in heterostructures. Compared to pristine SnO 2 , the band gap of the heterostructures is much smaller, leading to their absorption wavelength extending the entire visible region. Interestingly, a staggered type-II band alignment in the C 20 (C 60 )/SnO 2 (101) heterostructures results into the robust separation of photoexcited charge carriers between the two constituents, indicating that the fullerene is an effective sensitizer, and thus enhanced photocatalytic activity. These findings can rationalize the available experiment and will be of broad interest in developing the highly efficient semiconductor photocatalysts via fullerene modification.

Carbon nanotubes (CNTs)/two-dimensional transition metal dichalcogenides (MX2) hybrids have shown unique physical properties, making them promising materials for various applications ranging from photocatalysis to solar energy conversion. Understanding the interfacial interactions is highly desirable for designing these hybrids having excellent performance. Here, we systematically study the interfacial interaction in single-walled CNT/monolayer MoS2 hybrids and its effects on electronic and optical properties by first-principles calculations. It is found that the CNT is interacted noncovalently with monolayer MoS2, forming van der Waals heterostructures, and their interfacial interaction is closely related to tube diameter. In these hybrids, interestingly, MoS2 gaining or losing electrons depends also on tube diameter: (3,0)CNT would gain some electrons from MoS2, whereas other CNTs lose some electrons. The small band gap makes these hybrids have a strong optical absorption in the visible-light region. Th...

Promoting the spatial separation of photoexcited charge carriers is of paramount significance for photocatalysis. In this work, binary g-C 3 N 4 /CeO 2 nanosheets are first prepared by pyrolysis and subsequent exfoliation method, then decorated with ZnO nanoparticles to construct g-C 3 N 4 /CeO 2 /ZnO ternary nanocomposites with multi-heterointerfaces. Notably, the type-II staggered band alignments existing between any two of the constituents, as well as the efficient three-level transfer of electron-holes in unique g-C 3 N 4 /CeO 2 /ZnO ternary composites, leads to the robust separation of photoexcited charge carriers, as verified by its photocurrent increased by 8 times under visible light irradiation. The resulting g-C 3 N 4 /CeO 2 /ZnO ternary nanocomposites unveil appreciably increased photocatalytic activity, faster than that of pure g-C 3 N 4 , ZnO and g-C 3 N 4 /CeO 2 by a factor of 11, 4.6 and 3.7, respectively, and good stability toward methylene blue (MB) degradation. The remarkably enhanced photocatalytic activity of g-C 3 N 4 /CeO 2 /ZnO ternary heterostructures can be interpreted in terms of lots of active sites of nanosheet shapes and the efficient charge separation owing to the resulting type-II band alignment with more than one heterointerface and the efficient three-level electron-hole transfer. A plausible mechanism is also elucidated via active species trapping experiments with various scavengers, which indicating that the photogenerated holes and •OH radicals play a crucial role in photodegradation reaction under visible light irradiation. This work suggest that the rational design and construction of type II multi-heterostructures is powerful for developing highly efficient and reusable visible-light photocatalysts for environmental purification and energy conversion.

Multilayer van der Waals (vdW) heterostructures assembled by diverse atomically thin layers have demonstrated a wide range of fascinating phenomena and novel applications. Understanding the interlayer coupling and its correlation effect is paramount for designing novel vdW heterostructures with desirable physical properties. Using a detailed theoretical study of two-dimensional (2D) MoS2-graphene (GR)-based heterostructures based on state-of-the-art hybrid density functional theory, we reveal that for 2D few-layer heterostructures, vdW forces between neighboring layers depend on the number of layers. Compared to that in the bilayer, the interlayer coupling in trilayer vdW heterostructures can significantly be enhanced by stacking the third layer, directly supported by short interlayer separations and more interfacial charge transfer. The trilayer shows strong light absorption over a wide range (

The energetic alignment of band edges at the interface plays a central role in determining the properties and applications of two-dimensional (2D) van der Waals (vdW) heterostructures. Generally, three conventional heterojunction types (type-I, type-II, and type-III) have widely been investigated and used in diverse fields. Unconventional band alignments (type-IV, type-V, and type-VI) are, however, hitherto unreported in the vdW heterostructures. We find that 2D binary semiconductors composed of group IV–V elements manifest a similar electronic structure, offering in principle the possibility of designing heterostructures with novel band alignments due to the hybridization of band-edge states. We first show here that a 2D SiAs/GeP heterostructure exhibits a type-VI band alignment, which is induced by the interlayer pz orbital hybridization, and a transition of band alignment from type-VI to type-V occurs when strain or electric field is applied over a critical value. The unconventional band alignments and their transition natures enable broad application of these vdW heterostructures in special opto-electronic devices and energy conversion.

Generating irreducible site-occupancy configurations by taking advantage of crystal symmetry is a ubiquitous method for accelerating of disordered structure prediction, which plays an important role in condensed matter physics and material science. Here, we present a new algorithm for generating irreducible site-occupancy configurations, that works for arbitrary parent cell with any supercell expansion matrix, and for any number of atom types with arbitrary stoichiometry. The new algorithm identifies the symmetrically equivalent configurations by searching the space group operations of underlying lattice and building the equivalent atomic matrix based on it. Importantly, an integer representation of configurations can greatly accelerate the speed of elimination of duplicate configurations, resulting into a linear scale of run time with the number of irreducible configurations that finally found. Moreover, based on our new algorithm, we write the corresponding code named as disorder in FORTRAN programming language, and the performance test results show that the time efficiency of our disorder code is superior to that of other related codes (supercell, enumlib and SOD)., Comment: 23 pages, 2 tables, 6 figures and 33 references