Regioselective super-assembly of Prussian blue analogue.

The construction of high-asymmetrical structures demonstrates significant potential in improving the functionality and distinctness of nanomaterials, but remains a considerable challenge. Herein, we develop a one-pot method to fabricate regioselective super-assembly of Prussian blue analogue (PBA) -- a PBA anisotropic structure (PBA-AS) decorated with epitaxial modules--using a step-by-step epitaxial growth on a rapidly self-assembled cubic substrate guided by thiocyanuric acid (TCA) molecules. The epitaxial growth units manifest as diverse geometric shapes, which are predominantly concentrated on the {100}, {111}, or {100}+{111} crystal plane of the cubic substrate. The crystal plane and morphology of epitaxial module can be regulated by changing the TCA concentration and reaction temperature, enabling a high level of controllability over specific assembly sites and structures. To illustrate the advantage of the asymmetrical structure, phosphated PBA-AS demonstrates improved performance in the oxygen evolution reaction compared to simple phosphated PBA nanocube. This method offers valuable insights for designing asymmetrical nanomaterials with intricate architectures and versatile functionalities.

Rapid Construction of Double Crystalline Prussian Blue Analogue Hetero-Superstructure.

The controllable construction of complex metal-organic coordination polymers (CPs) merits untold scientific and technological potential, yet remains a grand challenge of one-step construction and modulating simultaneously valence states of metals and topological morphology. Here, a thiocyanuric acid (TCA)-triggered strategy is presented to one-step rapid synthesis a double-crystalline Prussian blue analogue hetero-superstructure (PBA-hs) that comprises a Co3[Fe(CN)6]2 cube overcoated with a KCo[Fe(CN)6] shell, followed by eight self-assembled small cubes on vertices. Unlike common directing surfactants, TCA not only acts as a trigger for the fast growth of KCo[Fe(CN)6] on the Co3[Fe(CN)6]2 phase resulting in a PBA-on-PBA hetero-superstructure, but also serves as a flange-like bridge between them. By combining experiments with simulations, a deprotonation-induced electron transfer (DIET) mechanism is proposed for formation of second phase in PBA-hs, differing from thermally and photo-induced electron transfer processes. To prove utility, the calcined PBA-hs exhibits enhanced oxygen evolution reaction performance. This work provides a new method to design of novel CPs for enriching chemistry and material science. This work offers a practical approach to design novel CPs for enriching chemistry and material science.

Dipole Effect on Oxygen Evolution Reaction of 2D Janus Single-Atom Catalysts: A Case of Rh Anchored on the P6m2-NP Configurations.

Catalytic performance of single-atom catalysts (SACs) relies fundamentally on the electronic nature and local coordination environment of the active site. Here, based on a machine-learning (ML)-aided density functional theory (DFT) method, we reveal that the intrinsic dipole in Janus materials has a significant impact on the catalytic activity of SACs, using 2D γ-phosphorus carbide (γ-PC) as a model system. Specifically, a local dipole around the active site is a key degree to tune the catalytic activity and can be used as an important descriptor with a high feature importance of 17.1% in predicting the difference of adsorption free energy (ΔGO* - ΔGOH*) to assess the activity of the oxygen evolution reaction. As a result, the catalytic performance of SACs can be tuned by an intrinsic dipole, in stark contrast to those external stimuli strategies previously used. These results suggest that dipole engineering and the revolutionary DFT-ML hybrid scheme are novel approaches for designing high-performance catalysts.

Synergistic effect of composition gradient and morphology on the catalytic activity of amorphous FeCoNi-LDH.

The rational design of electrocatalysts with well-designed compositions and structures for the oxygen evolution reaction (OER) is promising and challenging. Herein, we developed a novel strategy - a one-step double-cation etching sedimentation equilibrium strategy - to synthesize amorphous hollow Fe-Co-Ni layered double hydroxide nanocages with an outer surface of vertically interconnected ultrathin nanosheets (Fe-Co-Ni-LDH), which primarily depends on the in situ etching sedimentation equilibrium of the template interface. This unique vertical nanosheet-shell hierarchical nanostructure possesses enhanced charge transfer, increased active sites, and favorable kinetics during electrolysis, resulting in superb electrocatalytic performance for the oxygen evolution reaction (OER). Specifically, the Fe-Co-Ni-LDH nanocages exhibited remarkable OER activity in alkaline electrolytes and achieved a current density of 100 mA cm-2 at a low overpotential of 272 mV with excellent stability. This powerful strategy provides a profound molecular-level insight into the control of the morphology and composition of 2D layered materials.

Oxygen Defect Engineering Promotes Synergy Between Adsorbate Evolution and Single Lattice Oxygen Mechanisms of OER in Transition Metal-Based (oxy)Hydroxide.

The oxygen evolution reaction (OER) activity of transition metal (TM)-based (oxy)hydroxide is dominated by the number and nature of surface active sites, which are generally considered to be TM atoms occupying less than half of surface sites, with most being inactive oxygen atoms. Herein, based on an in situ competing growth strategy of bimetallic ions and OH- ions, a facile one-step method is proposed to modulate oxygen defects in NiFe-layered double hydroxide (NiFe-LDH)/FeOOH heterostructure, which may trigger the single lattice oxygen mechanism (sLOM). Interestingly, by only varying the addition of H2 O2 , one can simultaneously regulate the concentration of oxygen defects, the valence of metal sites, and the ratio of components. The proper oxygen defects promote synergy between the adsorbate evolution mechanism (AEM, metal redox chemistry) and sLOM (oxygen redox chemistry) of OER in NiFe-based (oxy)hydroxide, practically maximizing the use of surface TM and oxygen atoms as active sites. Consequently, the optimal NiFe-LDH/FeOOH heterostructure outperforms the reported non-noble OER catalysts in electrocatalytic activity, with an overpotential of 177 mV to deliver a current density of 20 mA cm-2 and high stability. The novel strategy exemplifies a facile and versatile approach to designing highly active TM-LDH-based OER electrocatalysts for energy and environmental applications.

A General Strategy for Synthesis of Binary Transition Metal Phosphides Hollow Sandwich Heterostructures.

The hollow sandwich core-shell micro-nanomaterials are widely used in materials, chemistry, and medicine, but their fabrication, particularly for transition metal phosphides (TMPs), remains a great challenge. Herein, a general synthesis strategy is presented for binary TMPs hollow sandwich heterostructures with vertically interconnected nanosheets on the inside and outside surfaces of polyhedron FeCoPx /C, demonstrated by a variety of transition metals (including Co, Fe, Cd, Mn, Cu, Cr, and Ni). Density functional theory (DFT) calculation reveals the process and universal mechanism of layered double hydroxide (LDH) growth on Prussian blue analog (PBA) surface in detail for the first time, which provides the theoretical foundations for feasibility and rationality of the synthesis strategy. This unique structure exhibits a vertical nanosheet-shell-vertical nanosheet configuration combining the advantages of sandwich, hollow and vertical heterostructures, effectively achieving their synergistic effect. As a proof-of-concept of their applications, the CoNiPx @FeCoPx /C@CoNiPx hollow sandwich polyhedron architectures (representative samples) show excellent catalytic performance for the oxygen evolution reaction (OER) in alkaline electrolytes. This work provides a general method for constructing hollow-sandwich micro-nanostructures, which provides more ideas and directions for design of micro-nano materials with special geometric topology.

Directional Charge Transfer Channels in a Monolithically Integrated Electrode for Photoassisted Overall Water Splitting.

Photoelectrocatalytic performance of a system is fundamentally determined by the full absorption of sunlight and high utilization of photoexcited carriers, but efficiency of the latter is largely limited by inefficient charge transfer from the absorber to reactive sites. Here, we propose to construct directional charge transfer channels in a monolithically integrated electrode, taking carbon dots/carbon nitride (CCN) nanotubes and FeOOH/FeCo layered double hydroxide (FFC) nanosheets as a representative, to boost the photoassisted overall water splitting performance. Detailed experimental investigations and DFT calculations demonstrate that the interfacial C-O-Fe bonds between CCN and FFC act as charge transfer channels, facilitating the directional migration of the photogenerated carriers between CCN and FFC surfaces. Moreover, the in situ oxidized Fe/Co species by photogenerated holes trigger lattice oxygen activation, realizing the construction of the Fe-Co dual-site as the catalytic center and efficiently lowering the barrier energy for water oxidation. As a result, the CCN@FFC electrode shows multiple functionalities in photoelectrocatalysis: only a low overpotential of 68 mV, 182 mV, and 1.435 V is required to deliver 10 mA cm-2 current densities for the photoassisted HER, OER, and overall water splitting, respectively. This directional charge transfer modulation strategy may facilitate the design of highly active and cost-effective multifunctional catalysts for energy conversion and storage.

Application of the hospital-family holistic care model in caregivers of patients with permanent enterostomy: A randomized controlled trial.

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 < 0.05) based on the t tests, and the psychological distress was lower than that in the control group. The ostomy adaptability of the control group was significantly lower than that in the intervention group (p < 0.001) based on the t tests, and the χ2 test showed that ostomy complication was more than that in the intervention group (23.81% vs. 12.90% and 34.92% vs. 19.35%; p < 0.05) at 3 and 6 months after discharge. The interaction between time and group showed that the effect of time factor varied with the group and the four evaluation indexes in the intervention group gradually improved with the extension of the observation time and were better than those in the control group based on generalized estimating equation model. CONCLUSION: The hospital-family holistic care model based on 'Timing It Right' can effectively improve the care ability of caregivers of patients with permanent enterostomy, reduce psychological distress, and improve the quality of life. IMPACT: The caregivers of patients with permanent enterostomy showed dynamic changes in their care experience and needs at different stages of the disease. The hospital-family holistic care intervention strategy based on 'Timing It Right' can effectively improve the caregiver's care ability, alleviate psychological distress, and improve the quality of life. Additionally, improving the patients' stoma adaptability and reducing the incidence of complications related to ostomy.

Strain and Electric Field Controllable Schottky Barriers and Contact Types in Graphene-MoTe2 van der Waals Heterostructure.

Two-dimensional (2D) transition metal dichalcogenides with intrinsically passivated surfaces are promising candidates for ultrathin optoelectronic devices that their performance is strongly affected by the contact with the metallic electrodes. Herein, first-principle calculations are used to construct and investigate the electronic and interfacial properties of 2D MoTe2 in contact with a graphene electrode by taking full advantage of them. The obtained results reveal that the electronic properties of graphene and MoTe2 layers are well preserved in heterostructures due to the weak van der Waals interlayer interaction, and the Fermi level moves toward the conduction band minimum of MoTe2 layer thus forming an n type Schottky contact at the interface. More interestingly, the Schottky barrier height and contact types in the graphene-MoTe2 heterostructure can be effectively tuned by biaxial strain and external electric field, which can transform the heterostructure from an n type Schottky contact to a p type one or to Ohmic contact. This work provides a deeper insight look for tuning the contact types and effective strategies to design high performance MoTe2-based Schottky electronic nanodevices.

Type-II/type-II band alignment to boost spatial charge separation: a case study of g-C3N4 quantum dots/a-TiO2/r-TiO2 for highly efficient photocatalytic hydrogen and oxygen evolution.

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.

Organic Small Molecule Activates Transition Metal Foam for Efficient Oxygen Evolution Reaction.

Developing low-cost, highly efficient, and durable electrocatalysts for oxygen evolution reaction (OER) is essential for the practical application of electrochemical water splitting. Herein, it is discovered that organic small molecule (hexabromobenzene, HBB) can activate commercial transition metal (Ni, Fe, and NiFe) foam by directly evolving metal nanomeshes embedded in graphene-like films (M-NM@G) through a facile Br-induced solid-phase migration process. Systematic investigations indicate that HBB can conformally generate graphene-like network on bulk metal foam substrate via the cleavage of CBr bonds and the formation of CC linkage. Simultaneously, the cleaved CBr fragments can efficiently extract metal atoms from bulk substrate, in situ producing transition metal nanomeshes embedded in the graphene-like films. As a result, such functional nanostructure can serve as an efficient OER electrocatalyst with a low overpotential and excellent long-term stability. Specifically, the overpotential at 100 mA cm-2 is only 208 mV for NiFe-NM@G, ranking the top-tier OER electrocatalysts. This work demonstrates an intriguing general strategy for directly transforming bulk transition metals into nanostructured functional electrocatalysts via the interaction with organic small molecules, opening up opportunities for bridging the application of organic small molecules in energy technologies.

Interfacial charge modulation: carbon quantum dot implanted carbon nitride double-deck nanoframes for robust visible-light photocatalytic tetracycline degradation.

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.

A design rule for two-dimensional van der Waals heterostructures with unconventional band alignments.

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.

Effects of hospital-family holistic care model on the health outcome of patients with permanent enterostomy based on the theory of 'Timing It Right'.

AIMS AND OBJECTIVES: To explore the effects of hospital-family holistic care model based on 'Timing It Right' on the health outcome of patients with permanent colostomy. BACKGROUND: Colorectal cancer is a common malignant tumour of digestive system, which seriously threatens human life and health. Colostomy is one of the main treatments for colorectal cancer, which effectively improves the 5-year survival rate of patients. However, the postoperative psychological and physiological rehabilitation nursing is still faced with great challenges due to the change of body image and defecation pathway caused by colostomy. METHODS: A randomised controlled trial was conducted, and 119 patients with permanent enterostomy were randomly divided into two groups, with 60 cases in the intervention group and 59 cases in the control group. The intervention group received routine care follow-up and hospital-family holistic care intervention based on 'Timing It Right', while the control group received routine care and follow-up. The resilience, self-care ability, complications and life quality of patients with permanent enterostomy were compared between two groups before intervention, at discharge, 3 months and 6 months after discharge. CONSORT checklist was applied as the reporting guideline for this study (see Appendix S1). RESULTS: A total of 108 patients with permanent enterostomy completed the study (90.76%). At 3 months and 6 months after discharge, the resilience and quality of life in the intervention group were significantly better than those in the control group (t = 4.158 vs. 7.406, t = 4.933 vs. 8.611, p < .05), while the complications in the intervention group were significantly lower than that in the control group (25.5% vs. 41.51%, 14.45% vs. 30.19%; p < .05). The self-care ability of the intervention group was significantly better than that in the control group (t = 1.543 vs. 3.656 vs. 6.273, p < .05) at discharge, 3 months and 6 months after discharge. The interaction between time and grouping showed that the effect of time factor varied with the grouping. After intervention, there were significant differences in psychological resilience, self-care ability, complications and quality of life between the two groups at different observation points (p < .01). The three evaluation indices of intervention group increased with the migration of observation time points and were significantly better than those of control group, especially the quality of life (84.35 ± 4.25 vs. 60.45 ± 8.42, p < .01). CONCLUSIONS: The hospital-family holistic care model based on 'Timing It Right' can effectively improve the psychological resilience, self-care ability and quality of life; reduce complications; and improve the health outcomes of patients with permanent enterostomy. RELEVANCE TO CLINICAL PRACTICE: Patients with permanent enterostomy have different needs for nursing care at different stages of the disease, and they are dynamically changing. The hospital-family holistic care model based on 'Timing It Right' can effectively improve the health outcomes of patients with permanent enterostomy, which is worthy of clinical application.

Hierarchical Self-assembly of Well-Defined Louver-Like P-Doped Carbon Nitride Nanowire Arrays with Highly Efficient Hydrogen Evolution.

Self-assembled nanostructure arrays integrating the advantages of the intrinsic characters of nanostructure as well as the array stability are appealing in advanced materials. However, the precise bottom-up synthesis of nanostructure arrays without templates or substrates is quite challenging because of the general occurrence of homogeneous nucleation and the difficult manipulation of noncovalent interactions. Herein, we first report the precisely manipulated synthesis of well-defined louver-like P-doped carbon nitride nanowire arrays (L-PCN) via a supramolecular self-assembly method by regulating the noncovalent interactions through hydrogen bond. With this strategy, CN nanowires align in the outer frame with the separation and spatial location achieving ultrastability and outstanding photoelectricity properties. Significantly, this self-assembly L-PCN exhibits a superior visible light-driven hydrogen evolution activity of 1872.9 µmol h-1 g-1, rendering a ~ 25.6-fold enhancement compared to bulk CN, and high photostability. Moreover, an apparent quantum efficiency of 6.93% is achieved for hydrogen evolution at 420 ± 15 nm. The experimental results and first-principles calculations demonstrate that the remarkable enhancement of photocatalytic activity of L-PCN can be attributed to the synergetic effect of structural topology and dopant. These findings suggest that we are able to design particular hierarchical nanostructures with desirable performance using hydrogen-bond engineering.

Penta-Graphene as a Potential Gas Sensor for NOx Detection.

Two-dimensional (2D) penta-graphene (PG) with unique properties that can even outperform graphene is attracting extensive attention because of its promising application in nanoelectronics. Herein, we investigate the electronic and transport properties of monolayer PG with typical small gas molecules, such as CO, CO2, NH3, NO and NO2, to explore the sensing capabilities of this monolayer by using first-principles and non-equilibrium Green's function (NEGF) calculations. The optimal position and mode of adsorbed molecules are determined, and the important role of charge transfer in adsorption stability and the influence of chemical bond formation on the electronic structure of the adsorption system are explored. It is demonstrated that monolayer PG is most preferred for the NOx (x = 1, 2) molecules with suitable adsorption strength and apparent charge transfer. Moreover, the current-voltage (I-V) curves of PG display a tremendous reduction of 88% (90%) in current after NO2 (NO) adsorption. The superior sensing performance of PG rivals or even surpasses that of other 2D materials such as graphene and phosphorene. Such ultrahigh sensitivity and selectivity to nitrogen oxides make PG a superior gas sensor that promises wide-ranging applications.

Strategy to boost catalytic activity of polymeric carbon nitride: synergistic effect of controllable in situ surface engineering and morphology.

Polymeric carbon nitride (CN) is a promising metal-free catalyst plagued by a low intrinsic activity. Herein, a novel strategy based on controllable in situ surface engineering and morphology was developed to synergistically boost the catalytic activity of CN by tuning the hydroxyl groups on its surface and constructing a unique nanostructure. The controllable introduction of hydroxyl groups on CN nanoshells, prepared by the thermal condensation of oxygen-containing supramolecular precursors formed in water, led to spatial separation of the HOMO and LUMO, and effective exciton dissociation, as verified by experiments and ab initio calculations. Furthermore, the hollow hemispherical nanoshell endowed more exposed active sites, optimal mass transport, and dynamic modulations. The optimized hollow hemispherical CN nanoshells exhibited remarkable catalytic activity, with a photoelectrocatalytic OER overpotential of about 330 mV at a current density of 10 mA cm-2, outperforming state-of-the-art precious-metal catalyst IrO2. High activity for the visible-light photocatalytic HER and pollutant degradation were also observed. This study proposes that, through rational surface group modification, a polymer material with high catalytic activity can be practically realized, which is promising for the design of efficient metal-free catalysts.

Monolayer Phosphorene-Carbon Nanotube Heterostructures for Photocatalysis: Analysis by Density Functional Theory.

One-dimensional (1D)/2D heterostructures have attracted great attention in electronic and optoelectronic fields because of their unique geometrical structures and rich physics. Here, we systematically explore electronic structure and optical performance of single-wall carbon nanotube (CNT)/phosphorene (BP) hybrids by large-scale density functional theory (DFT) computation. The results show that the interfacial interaction between CNT and BP is a weak van der Waals (vdW) force and correlates with tube diameter of CNTs. The CNT/BP hybrids have strong optical absorption compared with that of individual BP and CNT. A diameter-dependent type I or II heterojunction in CNT/BP hybrids is observed. Moreover, CNTs can not only significantly promote photogenerated carrier transfer, but also effectively improve the photocatalytic activities of BP as a co-catalyst. These findings would enrich our understanding of BP-based 1D/2D heterostructures, providing further insight into the design of highly efficient phosphorene-based or CNT-based nanophotocatalysts.

Doping-Induced Hydrogen-Bond Engineering in Polymeric Carbon Nitride To Significantly Boost the Photocatalytic H2 Evolution Performance.

Unlike graphene, graphitic carbon nitride (CN) polymer contains a weak hydrogen bond and van der Waals (vdWs) interactions besides a strong covalent bond, which controls its final morphology and functionality. Herein, we propose a novel strategy, hydrogen-bond engineering, to tune hydrogen bonds in polymeric CN through nonmetal codoping. Incorporation of B and P dopants breaks partial hydrogen bonds within the layers and simultaneously weakens the vdWs interaction between neighboring layers, resulting in ultrathin codoped CN nanosheets. The two-dimensional structure of the ultrathin sheet, broken hydrogen bonds, and incorporated dopants endow them with efficient visible light harvesting, improved charge separation, and increased active edge sites that synergistically enhance the photocatalytic activity of doped CN. Specifically, the B/P-codoped CN exhibits an extremely high hydrogen-evolution rate of 10877.40 µmol h-1 g-1, much higher than most reported values of CN. This work demonstrates that hydrogen bond engineering is an effective strategy to modify the structure and properties of polymers for various applications.

Doping-induced enhancement of crystallinity in polymeric carbon nitride nanosheets to improve their visible-light photocatalytic activity.

Structural defects can greatly inhibit electron transfer in two-dimensional (2D) layered polymeric carbon nitride (CN) unit, seriously lowering its utilization ratio of photogenerated charges during photocatalysis. Herein, we propose a new strategy based on intra-melon hydrogen bonding interactions in 2D CN frameworks to improve the crystallinity of CN. This concept was validated by removing some amino groups and connecting melon using codoped B and F atoms via a simple one-step sodium fluoroborate-assisted thermal treatment. The enhancement in crystallinity effectively promoted exciton dissociation and charge transfer in the CN nanosheets. Furthermore, the B/F dopants also improved the separation of photogenerated carriers by promoting charge capture. The highly efficient visible-light photocatalytic activity of the crystalline B/F-codoped CN nanosheets was demonstrated by degrading methyl orange, Rhodamine B, colorless phenol and tetracycline hydrochloride as models, where their degradation rate constant was more than 10, 5, 32 and 3 times higher than that of pure CN, respectively. Moreover, the B/F-codoped CN exhibited an excellent photoelectrocatalytic performance for the oxygen evolution reaction (OER), outperforming the precious-metal IrO2 catalyst. The simple and effective strategy proposed herein provides a direct route to engineer high crystallinity in 2D materials for tunable charge carrier separation and migration for electronic and optoelectronic applications.