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Strong photo-generated charge recombination within graphitic carbon nitride and the lack of suitable co-catalysts with selective high catalytic reaction activity have hindered the effective photocatalytic hydrogen peroxide production. In this work, a series of 2D co-catalyst nitrogen-doped graphenes with the different bond states of doped nitrogen were synthesized under modified synthetic conditions, resulting in different surface catalytic hydrogen peroxide generation activities. Electrochemical analysis proves that pyrrolic nitrogen doped in graphene plays an important role in improving two-electron-transferring reactions on the surface of nitrogen-doped graphene for hydrogen peroxide generation, which depresses further reduction of hydrogen peroxide into hydroxyl radicals. Benefiting from the synergistic role of improved charge separation and enhanced surface-selective reaction activity of the co-catalyst nitrogen-doped graphene, 2D/2D graphitic carbon nitride/nitrogen-doped graphene heterostructure composites produce 56.22 μmol hydrogen peroxide under visible light irradiation in 4 h, which is 2.77 times higher than the 20.28 μmol of pure graphitic carbon nitride.

Micro-supercapacitor is a member of the miniaturized energy storage device family, which offers great advantages on power density and life span. However, the limited device capacitance and narrow voltage window limit its energy density, hindering its application. In the present work, a novel micro-pseudocapacitor (MPC) constructed via the facile extrusion-based 3D printing technique has been demonstrated to deliver efficient charge storage with high device capacitance and moderate voltage window. Such an asymmetric MPC is constructed with 3D-printing-enabled asymmetric interdigitated cellular microelectrodes; in which, one is Ni–Co–O nanosheets grown on macroporous 3D reduced GO (3DG) microelectrode and the other is MnO2 nanosheets grown on 3DG. Such an MPC offers facilitated fast electron transport, ionic diffusion, large number of active sites and desired porosity for electrolyte penetration. The asymmetric MPC shows a high specific capacity of 500 mC cm−2, an energy density of 90 μW h cm−2 and a voltage window of 1.3 V. A device cycling stability with 10 000 charge and discharge cycles is also achieved for the as-fabricated asymmetric MPCs. These encouraging results may open a new avenue to design and fabricate state-of-the-art miniaturized electrochemical energy storage devices with customized geometries.

Summary Pseudocapacitors with a fast faradic redox reaction during the electrochemical charge/discharge process hold great promise for delivering high power and high energy. Here, we used emerging oxygenated carbon nitride (OCN) as a model for nitrogen- and oxygen-enriched carbons and found an anion-selective charging behavior in aqueous electrolytes. The N- and O-mediated hydroxyl anion-selective charging originates from inbuilt surface-positive electrostatic potential localized at heptazine and quaternary N atom structural units. The carbon atoms in heptazine adjacent to pyridinic N act as the electron transfer active sites for faradic pseudocapacitance. The OCN free-standing films (FSFs) were developed as current collector-free electrodes, and stacking OCN FSFs can confer a cell with loading weight over a commercial level. For demonstration, a symmetrical cell with 17.7 mg cm−2 delivers an energy of 140.9 mW h at a high power of 2,499.9 mW, and almost 100% capacitance retention after 20,000 charge/discharge cycles at 50 mA.

Photocatalytic oxidation treatment is an emerging and fast developed eco-friendly, energy-saving, and efficient advanced oxidation technology for degrading hazardous pesticides. The conventional chemical detection to evaluate the effects for this process depends on the broken chemical structure, only giving residual content and product chemical composition. However, it misses direct visual detection on the toxicity and the quantitative analysis of pesticide detoxification. Here, we develop a novel strategy to combine photocatalytic oxidation with a zebrafish biological model to provide a direct visual detection on the environmental detoxification. The mortality or deformity of zebrafish embryos (ZEs) acts as an indicator. Over the irradiation duration threshold, the mortality of ZEs decreases to 23.3% for pure chlorothalonil (CTL-P) after photocatalytic oxidation treatment for 1 h, and the deformity reduces to 13.3% for commercial CTL (CTL-C) after 30 min and to 3.33% for tetramethylthiuram disulfide (TMTD) after 20 min. The toxicity of CTL-C and TMTD could be completely removed by photocatalytic oxidation treatment and causes no damage to the ZE developmental morphology. Chemical analyses demonstrate the degradation of CTL into inorganic compounds and TMTD into small organic molecules. Among these highlighted heterogeneous photocatalysts (g-C3N4, BiVO4, Ag3PO4, and P25), g-C3N4 exhibits the highest photocatalytic detoxification for CTL-P, CTL-C, and TMTD.

In this study, expanded graphite and natural graphite were introduced into resin-based friction materials, and the tribological behavior of the composites was investigated. The tribo-performance of the two friction composites was evaluated using a constant speed friction tester. The results showed that the expanded graphite composite (EGC) displayed better lubricity in both the fading and the recovery processes. The wear rate of the EGC decreased by 22.43% more than that of the natural graphite composite (NGC). In the fading process, and the EGC enhanced the stability of the coefficient of friction. The recovery maintenance rate of the NGC was 4.66% higher than that of the EGC. It can be concluded that expanded graphite plays an important role in the formation of a stable contact plateau and can effectively reduce the wear.

CdS, as semiconductor catalyst, has attracted much attention in photocatalytic production of hydrogen for the wide range utilization of visible light. Usually, noble metal deposited as a co-catalyst on CdS surface is required to achieve high photocatalytic activity. Thus, replacing noble metal via cheap and easy synthesis co-catalyst would be of great value for developing cost-effective photocatalyst. In this work, noble-metal-free defective Mo15S19 combined with CdS-diethylenetriamine (DETA) hybrid makes efficient separation of photoinduced carriers, and more importantly, reduced overpotential for hydrogen evolution reaction, thereby improved catalytic hydrogen evolution performance of designed composite. In particular, 3%Mo15S19/CdS-DETA systems exhibited a high rate of hydrogen production, reaching 3.61 mmol g−1 h−1, which is similar with 3%Pt/CdS-DETA and 9.5 and 2.19 times as high as that of CdS nanoparticles (NPs) and CdS-DETA, respectively. At the same time, photocorrosion resistance of 3%Mo15S19/CdS-DETA systems was dramatically improved. According to DFT theoretical calculations, it was found that the enhanced photocatalytic performance and anticorrosion are mainly due to efficient transfer of photoexcited electrons from CdS-DETA to Mo15S19.

Ag3PO4 is widely used in the field of photocatalysis because of its unique activity. However, photocorrosion limits its practical application. Therefore, it is very urgent to find a solution to improve the light corrosion resistance of Ag3PO4. Herein, the Z-scheme WO3(H2O)0.333/Ag3PO4 composites are successfully prepared through microwave hydrothermal and simple stirring. The WO3(H2O)0.333/Ag3PO4 composites are characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV-Vis spectroscopy. In the degradation of organic pollutants, WO3(H2O)0.333/Ag3PO4 composites exhibit excellent performance under visible light. This is mainly attributed to the synergy of WO3(H2O)0.333 and Ag3PO4. Especially, the photocatalytic activity of 15%WO3(H2O)0.333/Ag3PO4 is the highest, and the methylene blue can be completely degraded in 4 min. In addition, the stability of the composites is also greatly enhanced. After five cycles of testing, the photocatalytic activity of 15%WO3(H2O)0.333/Ag3PO4 is not obviously decreased. However, the degradation efficiency of Ag3PO4 was only 20.2%. This indicates that adding WO3(H2O)0.333 can significantly improve the photoetching resistance of Ag3PO4. Finally, Z-scheme photocatalytic mechanism is investigated.

Composite structure of montmorillonites(Mt)with graphene oxide (GO) or reduced graphene oxide (rGO) was successfully synthesized by grafting with 3-aminopropyl triethoxysilane (APTES) and hydrazine hydrate reduction. XRD, BET, FTIR, SEM and XPS analysis were used to characterize the surface and structure properties of the as-obtained products. Measurement results suggested that these two composites were similar in morphology and pore structure, but significantly different in the surface oxygenic groups. Adsorption properties of the Mt/GO and Mt/rGO were investigated using methylene blue (MB) as the target material. Compare to original Mt, APTES modified Mt and Mt/rGO, Mt/GO exhibited the highest adsorption capacity of 641.1 mg/g at the initial concentration of 750 mg/L, and MB was removed by 94.3% within 5min. Mechanism analysis suggested that the high absorption performance of the composite was determined by the high specific surface area, oxygenic groups of GO, high adsorption capacity of montmorillonite as well as the synergistic effect between the Mt and graphene oxide nanosheets.

Cobalt pentlandite (Co9S8) has recently emerged as a promising electrode material for energy storage devices. Herein, Co9S8/graphene hybrid is rationally synthesized through a facile hydrothermal method. Minor-sized Co9S8 flakes is finely-deposited on the surface of graphene sheet and an interconnected Co9S8/graphene architecture structure is obtained. The electrochemical test results show that Co9S8/graphene electrode delivers a remarkable charge capacity of 540 C g−1 within 1 min and 74.5% capacitance is retained within a discharge time of 14 s. A hybrid supercapacitor assembled with Co9S8-involved electrode delivers a high energy density of 37 Wh kg−1 at a power density of 170 W kg−1, and 15.3 Wh kg−1 can be maintained even at a high power density of 12 kW kg−1. The excellent electrochemical performance should be attributed to abundant active sites, enhanced charge-transfer characters and maximized capacitive contribution of Co9S8/graphene electrode.

Efficient anchoring of transitional metals on supporting materials with well-exposed metal atoms and tuned chemical bonds between them is crucially important for the design of high-performance electrocatalysts. In this study, we adopted a strategy of using defective carbon nanotubes to synthesize holey graphene oxide with tunable basal plane hole size. Via the in situ formation of cobalt clusters during the process of doping of nitrogen into holey graphene oxide, the obtained composite showed strong chemical bonding of highly exposed cobalt with nitrogen and carbon on the nitrogen-doped holey graphene. It was found that the basal plane hole of graphene was beneficial for the deposition of cobalt; detailed analysis showed that rich defects on the basal plane favored the doping of pyridinic nitrogen and graphitic nitrogen and enhanced the chemical bonding of cobalt with nitrogen; this improved the four-electron transfer selectivity of the ORR; thus, the effectively enhanced catalytic activity of composites was comparable to those of the commercial Pt/C catalyst; moreover, these composites exhibited superior stability than the commercial Pt/C catalyst.

Artificial photosynthesis based on semiconductor photocatalysts has attracted great attentions recent years for its advantage in clean energy applications. Environmental friendly metal free semiconducting graphitic carbon nitride, which can be synthesized via simple pyrolysis of cheap industrial resources at low cost, with visible light photocatalytic activity for hydrogen evolution, oxygen evolution, hydrogen peroxide production and reduction of carbon dioxide has been intensively studied in recent ten years. On the way of developing highly active photocatalysts, publications focusing on graphitic carbon nitride have been dramatically increased especially in recent five years. These researches have revealed some key issues, which includes morphology, atomic composition, basal plane structure and defects, composites and type of co-catalysts, influence photocatalytic activity of graphitic carbon nitride based materials from different aspects. These aspects include light absorption, charge separation/migration and surface reactions, which can be categorized into band structure and surface activity characters of graphitic carbon nitride based materials. This review is focusing on engineering band and surface of graphitic carbon nitride for artificial photosynthesis. Through reviewing the recent progress on graphitic carbon nitride based artificial photosynthesis researches, it may provide more comprehensive and in-depth understanding for further designing of highly activity photocatalysts based on graphitic carbon nitride.

Ce4+ and Ca2+ modified La2Zr2O7 samples, La2Zr2O7, (La0.8Ce0.2)2(Zr0.7Ce0.3)2O7.2 and (La0.6Ce0.2Ca0.2)2(Zr0.7Ce0.3)2O7, were prepared by the co-precipitation method to obtain enhanced thermos-physical properties. Compared with La2Zr2O7, (La0.8Ce0.2)2(Zr0.7Ce0.3)2O7.2 and (La0.6Ce0.2Ca0.2)2(Zr0.7Ce0.3)2O7 both exhibited better sintering resistance, lower thermal conductivities, and higher thermal expansion coefficients. The underlying mechanism of the improved thermo-physical performance of La2Zr2O7 induced by Ce4+ and Ca2+ doping was discussed. The thermal conductivity and thermal expansion coefficient of (La0.6Ce0.2Ca0.2)2(Zr0.7Ce0.3)2O7 were 1.165 W·m−1·K−1 at 1450°C and 10.91 × 10−6 K−1, respectively, making it a promising material for the thermal barrier coatings (TBCs).

Manipulation structure of graphitic carbon nitride (GCN) to tune its photophysical and interfacial redox activity is one of fundamental issues for understanding and improving its photocatalytic hydrogen evolution (PHE) activity. In this work, we report our recent progress on manipulating structure of GCN via an easy and effective approach. Trace level iron is found to have increased atomic concentration and tuned bond state of carbon in structure manipulated GCN (M-GCN) along with porosity of it, which exhibits higher interfacial redox and photophysical activity than GCN. The improved interfacial redox and photophysical activities of M-GCN are found to have synthetic enhanced consumption of photo-generated electrons and holes during photocatalysis process and reduction of their recombination, which results in promotion of its PHE activity. PHE rate for M-GCN is found to be 2286 μmol−1 g−1 h−1, which is 2.82 time of GCN.

In solid-state electrolytes, the large resistance at grain boundaries remains the bottleneck for high ionic conductivity. Here we develop an alternative and somewhat counterintuitive strategy to enhance their ionic conductivity via non-equilibrium microstructure. Using Li1.4Al0.4Ti1.6(PO4)3 as an example, we demonstrate that semi-crystalline interphase between well crystallized ceramic phase and amorphous glass phase can be induced by spark plasma sintering, resulting in total ionic conductivity of 1.3 × 10−3 S cm−1 without any doping, which is 2 orders of magnitude higher than that derived by the conventional method. It is further demonstrated that the non-equilibrium structure is stable in ambient condition, yet can be converted into equilibrium structure by annealing with higher crystallinity but much lower ionic conductivity, proving that the non-equilibrium structure is indeed the key to the high performance. This opens door for its applications in electric vehicles, and the strategy is applicable to other ionic systems as well.

The Feasibility of interfacial redox reaction has determinant role in hydrogen evolution during photocatalytic water-splitting process. Here, we report that promoting interfacial oxidation ability of porous graphitic carbon nitride (Pg-C3N4) with defects can effectively improve visible light photocatalytic hydrogen evolution (PHE) activity. Pg-C3N4 with edge site defects was fabricated by constraining growth of g-C3N4 on porous kaolinite-derived template. The Pg-C3N4 with extra electrons of defects caused by enriched basal plane holes exhibits higher electrocatalytic activity for oxidation process in comparison with reduction process. This feature benefits electron-transfer reaction to quench photo-excited holes during photocatalysis process and promote photoelectrons reaction, which was proved by photoluminescence spectra of Pg-C3N4 and g-C3N4 and different PHE activity variation of their heterojunction materials with TiO2. The results show that PHE rate for Pg-C3N4 reaches 1917 umol−1 g−1 h−1, 2.37 times of g-C3N4 under visible light irradiation. This approach of engineering interfacial defects to accelerate hole’s oxidation reactions during photocatalytic water-splitting would advance two-dimensional (2D) catalysis for solar fuel production.

Cadmium sulfide (CdS) is a promising semiconductor material for photocatalytic hydrogen (H2) evolution. However, the serious photocorrosion and low visible-light utilization limit its practical application. In this work, cerium oxide (CeO2) modified inorganic-organic CdS-diethylenetriamine (CeO2/CdS-DETA) composite material with different mass ratios was fabricated by hydrothermal method. Crystal structure, light absorption properties, microstructure, photocatalytic H2 production activity, photocurrent and fluorescence spectra of the composites were investigated. The results exhibited that photocatalytic performance of CeO2/CdS-DETA materials was improved and 7%CeO2/CdS-DETA exhibited excellent catalytic activity (14.84 mmol g-1 h-1) under visible light irradiation (λ ≥ 420 nm), which is twice more than that of CdS-DETA. Moreover, the photocatalytic mechanism was preliminarily discussed. This work not only promotes the development of novel inorganic-organic CdS-DETA-based photocatalytic materials for solar energy utilization but provides sustainable photocatalysts by taking both photocatalytic H2 production and repeated utilization into consideration.

Reduced graphene oxide nanosheets modified with rich carbonyl groups (C=O) was obtained through a facile dehydration process by making use of the synergistic effect between phosphoric acid and monosodium phosphate. The product exhibited a high specific capacitance of 413 F g−1 at the current density of 0.25 A g−1 mainly owing to the high percentage of retained C=O groups which provided reversible pseudocapacitance and favored good dispersion. Additionally, the symmetric supercapacitors based on the modified graphene nanosheets showed high specific capacitance (314.2 F g−1 at 1 A g−1) and superior electrochemical stability with only 5.8% loss of its initial specific capacitance after 10000 cycle tests (at the current densities of 5 A g−1). The present work proposed an environmentally friendly way in controlling surface structure of reduced graphene oxide which promises great potential of graphene-based electrode materials for high performance energy-storage devices.

Carbon based nanomaterials have attracted great attentions in the fields of electrocatalysis and photocatalysis. Here, we report our recent progress on photocatalytic hydrogen evolution of graphitic carbon nitride (g-C3N4) by introducing carbon based electrocatalyst as co-catalyst. Cobalt/nitrogen doped graphitic carbon (Co-NG) composite with tubular structure was synthesized by cobalt catalyzed carbonization and graphitization of urea under thermal treatment. Co-NG with strong interaction of cobalt and nitrogen doped graphitic carbon has shown low overpotential for electrocatalytic hydrogen evolution reaction. It was thus used as co-catalyst for graphitic carbon nitride (g-C3N4). Beside enhanced light absorption and reduced recombination of Co-NG/g-C3N4 heterostructure composite, high interfacial redox reaction activity of Co-NG was found. The photocatalytic hydrogen evolution activity of Co-NG/g-C3N4 was thus effectively improved.

Tuning porous structure of carbon nanomaterials has been found to be important for their performance enhancement in electrochemical energy storage applications. In this work we employed a natural nanomaterial kaolinite, which is abundant and cheap, as hard template to synthesis porous carbon nanomaterial. By tuning the structure of hard template kaolinite, we have achieved a template directed formation of holey carbon nanosheet/nanotube materials. This carbon nanomaterials with hierarchical in-plane and out-of-plane pores have shown electrochemical energy storage capacity of 286 F/g (equal to 314 F/cm3) at 0.1 A/g and 85 F/g (equal to 93 F/cm3) at 100 A/g, which is comparable to variety of reported carbon based electrochemical energy storage electrode materials.

Atomically dispersed metals and their environments strongly influence their electrocatalytic activities. In this work, we synthesized a series of cobalt/nitrogen doped graphene (Co-NG) catalysts. Cobalt atom dispersion and aggregation on NG's basal plane, bond states of cobalt and nitrogen along with graphene basal plane defect and their impacts on hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities and kinetics were intensively studied. We found that a geometrically controlled formation of active Co N and Co C sites in the NG's basal plane is the key issue for improving interfacial Faradic reaction kinetics and thus enhancing hydrogen evolution. Differently, chemical bonding of finely dispersed cobalt atoms with oxygen, nitrogen and carbon together improves interfacial water oxidation kinetics for achieving high OER activity.

Carbon nanomaterials derived from biomass are considered as important sustainable energy carriers. In this study, we report an approach to synthesize cobalt/nitrogen doped carbon nanotubes (Co-NCNTs) for high oxygen reduction reaction (ORR) activity by cobalt catalyzed carbonization of biomass chitosan. It is found that the existence of cobalt results in the transition of graphene-like carbon nanosheets to tubular graphitic carbons. Moreover, a strong chemical bonding of cobalt with nitrogen and carbon in Co-NCNTs is found, which is important for enhancing the ORR activity. The Co-NCNT catalyst under optimized synthetic conditions displays attractive ORR activity superior to those of commercial Pt/C catalysts. Furthermore, the mechanism behind the enhanced ORR activity has also been studied. This study provides a feasible synthesis approach for the scalable production of biomass derived high performance carbon based ORR catalysts.

The narrow band-gap and long life-time of photo-generated charges endow CdS with much higher photocatalytic hydrogen evolution (PHE) activity over other photocatalysts. Thus, CdS based materials are considered to be most promising photocatalysts for PHE activity and stability. In this work, graphitic carbon nitride (GCN) is used as sacrifice agent to synthesize is nitrogen and carbon co-doped CdS nanoparticles with of uniform small size and higher specific surface area via hydrothermal reaction. Besides, co-doping of nitrogen and especially carbon leads to electron penetration to CdS results in tuned band structure of doped CdS with down-shifted conducting band and valance band positions. Moreover, the doped heteroatoms act as charge trapping centers that enhance charge separation within CdS particles endowing their photo-generated charges with longer life-time in compared with that of bare CdS. Benefited from non-metallic heteroatoms doping, obviously increased PHE activity and stability of CdS under visible light irradiation are achieved.

A novel hierarchical Ag2WO4/Ag/Bi2MoO6 ternary visible-light-driven photocatalyst was successfully synthesized by in situ doping Ag2WO4 with Bi2MoO6 nanosheets through a facile hydrothermal and photochemical process. The morphology, structure, optical performance and crystallinity of the products were measured by field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), UV–vis diffuse reflectance spectroscopy (DRS) and X-ray diffraction (XRD). The results showed that Ag2WO4/Ag was uniformly dispersed on the surface of Bi2MoO6 nanosheets. The photocatalytic performance of Ag2WO4/Ag/Bi2MoO6 heterostructures was evaluated by the degradation of methylene blue (MB) under 410 nm LED arrays. The ternary Ag2WO4/Ag/Bi2MoO6 nanocomposite exhibits higher photocatalytic activity than Bi2MoO6 and Ag2WO4. The synergistic effect of Ag2WO4 and Bi2MoO6 could generated more heterojunctions which promoted photoelectrons transfer from Ag2WO4 to Bi2MoO6, leading to the improvement of photocatalytic performance by photoelectrons-holes recombination suppression. At the same time, the surface plasmon resonance of Ag2WO4/Ag/Bi2MoO6 is another crucial reason for the high photocatalytic performance of organic pollutants degradation. And the 20 wt% Ag2WO4-loaded Bi2MoO6 shows the optimal photocatalytic performance in the degradation of MB. In addition, the ternary composites can be easily reclaimed by precipitation and exhibits high stability of photocatalytic degradation after five recycles.

Nitrogen-doped graphene (NG) was obtained from a facile and eco-friendly hydrothermal reaction and used as electrode materials for supercapacitors. The textural and chemical properties could be easily tuned by adjusting the basicity of the reaction environment. As the basic reaction conditions became stronger, the sheets of NG tended to stack together, the content of residual oxygen groups increased, but the nitrogen content decreased, which affected the electrochemical performance. The NG synthesized under a weak basic environment shows great pseudocapacitance and the largest electrochemical performance in a 6 mol L−1 KOH aqueous electrolyte when measured in a three-electrode system, which can be attributed to its randomly distributed and loosely stacked structure and high amount of residual oxygen atoms (12.8 at%). Furthermore, it presented excellent cycling stability with a capacitance retention ratio of 92.86% at the current densities of 5 A g−1 after 10 000 charge–discharge cycles in two-electrode configuration, which kept stable after 5000 cycles. These results implied that the NG sheets obtained by this simple eco-friendly approach are suitable for high performance supercapacitor applications.

The intrinsic morphology and basal plane defects on g-C 3 N 4 nanosheet have important influences on its electronic structures and photocatalytic activity. In this work, we report extending thermal treatment time of g-C 3 N 4 at 550 °C not only change the morphology of g-C 3 N 4 but also element composition of g-C 3 N 4 . The morphology variation results in largely increased SSA from 40.22 to 117.27 m 2 g −1 , obviously reduced pore size from 3.99 to 2.77 nm for g-C 3 N 4 and formation of in-plane holes. Moreover, composition variation of g-C 3 N 4 has also been found to have changed as the pyrolysis time extended. These changes have significant impact on the optical properties and photoelectrical characters of g-C 3 N 4 , which were investigated by UV-DSR, PL and Photocurrent measurement. The photocatalytic activity of g-C 3 N 4 obtained via 9 h thermal treatment at 550 °C has shown highest photocatalytic activity, which is 1.77 times than that of g-C 3 N 4 obtained via 3 h thermal treatment under visible irradiation and 1.99 times under UV irradiation respectively.

Manipulating basal plane structure of graphene for advanced energy conversion materials design has been research frontier in recent years. By extending size of defects in the basal plane of graphene from atomic scale to nanoscale, graphene with in-plane holes can be synthesized by multiple steps oxidation and reduction of defective graphene oxide at low concentration. These complicated and low yield synthetic methods largely limited research and applications of holey graphene based high performance energy conversion materials. Inspired by graphene in-plane holes formation mechanism, an easy and scalable synthetic approach has been proposed in this work. By oxidizing widely available defective graphite mineral under high concentration, holey graphene oxide has been scalable synthesized. Through simple reduction of holey graphene oxide, nitrogen doped holey graphene with high volumetric capacitance of 439 F/cm 3 was obtained. We believe this breakthrough can provide a feasible synthetic approach for further exploring the properties and performance of holey graphene based materials in variety of fields.

Inorganic-organic hybrid nanomaterials, with excellent chemical and physical properties and technology applications, have attracted much attention in many fields. In the photocatalytic field, it is still a problem to find a stable, adjustable morphology and band gap and effective photocatalyst in utilizing solar energy conversion to hydrogen (H2) to solve the energy crisis. Herein, with the assistance of diethylenetriamine (DETA), the novel inorganic-organic CdSe-DETA hybrids with different morphology and adjustable band gap have been synthesised via simple microwave hydrothermal method. The morphological transformation mechanism involves the consumption of organic components controlled by the mixed precursor and subsequent self-assembly of residual inorganic components (CdSe). Under the visible light irradiation (λ > 420 nm), CdSe-18DETA nanobelt, showed the best photocatalytic H2 production activity (5.75 mmol·g−1·h−1), which is 3.03 times greater than that of pure CdSe (1.90 mmol·g−1·h−1). Moreover, after four cycles, the photocatalytic H2 production activity can still remain 91.27% of initial value, which indicates its good photocatalytic stability. Our results provide a promising approach for designing visible-light photocatalysts with efficient electron-hole separation and adjustable morphology and band gap.

Developing a multiresponsive and multifunctional soft actuator that can output mechanical deformation is crucial to the fields of soft robotics and wearable devices. Herein, a 2D metallic molybdenum disulfide (MoS2)‐based soft actuator with dual‐response and self‐sensing function is designed and fabricated. By using the outstanding photothermal property of 1T phase MoS2, good electrical property and network structure of carbon nanotubes (CNTs), hygroscopic expansion of paper, and thermal expansion of polyimide (PI), the MoS2‐based actuator can respond to external voltage and light stimulation and produce rapid and large bending deformation. In addition, the actuator can be used as a flexible strain sensor to realize real‐time sensing of bending deformation by using piezoresistive property of the MoS2–CNT composite film. Based on this soft actuator, a flexible mechanical gripper that can manipulate soft objects with irregular shape and intelligent wearable gloves that can automatically close to block the light irradiation are made. Furthermore, combined with the sensing feature of this MoS2‐based actuator, the gripper with integrated sensing function is also developed. These results indicate the great prospect of the MoS2‐based actuator in intelligent soft mechanical devices, robots, and wearable systems.

Reduced graphene oxide (rGO) was prepared using oxalic acid in th e presence of montmorillonite (Mt) via hydrothermal treatment. The structure characterizations indicated that the porous structure of the obtained rGO and the residual oxygen groups were dominated by carbonyl and carboxyl groups. The mechanism analysis showed that the introduction of Mt. ensured the formation of isolated graphene oxide nanosheets free from being reduced by oxalic acid, further alleviating the irreversible restacking of rGO sheets. Electrochemical measurements demonstrated that the resultant rGO electrode offered a high specific capacitance (Cs) of 315 F/g at 1 A/g in a three-electrode configuration and the symmetric supercapacitor based on this electrode exhibited superior cycle stability with 89.7% capacitance retention after 10,000 cycles. This present work proposes a novel strategy for controlling the effects of oxalic acid on GO via employing multi-role Mt., also expands the preparation scope of graphene-based electrode materials.

The adsorption properties of two nanomorphologies of trititanate, nanotubes (TiNT) and plates (TiNP), prepared by the hydrothermal reaction of concentrated NaOH with different phases of TiO2, were examined. It was found that the capacity for both morphologies towards methylene blue (MB), an ideal pollutant, was extremely high, with the TiNP having a capacity of 130 mg/g, higher than the TiNT, whose capacity was 120 mg/g at 10 mg/L MB concentration. At capacity, the well-dispersed powders deposit on the floor of the reaction vessel. The two morphologies had very different structural and adsorption properties. TiNT with high surface area and pore volume exhibited exothermic monolayer adsorption of MB. TiNP with low surface area and pore volume yielded a higher adsorption capacity through endothermic multilayer adsorption governed by pore diffusion. TiNP exhibited a higher negative surface charge of −23 mV, compared to −12 mV for TiNT. The adsorption process appears to be an electrostatic interaction, with the cationic dye attracted more strongly to the nanoplates, resulting in a higher adsorption capacity and different adsorption modes. We believe this simple, low cost production of high capacity nanostructured adsorbent material has potential uses in wastewater treatment.

In this work, designed growth of two type of N-doped graphene nanosheets has been investigated using NH4H2PO4 and (NH4)2HPO4 as buffering agents, respectively, in a mild hydrothermal process. X-ray photoelectron spectroscopy (XPS) characterization indicates that the graphene nanosheets grown using NH4H2PO4 (NGC) have lower nitrogen but higher oxygen content than those using (NH4)2HPO4 (NGL). Electrochemical measurements in three-electrode systems show that both type of the graphene products exhibit superior electrochemical performance (383 and 356 F g-1 at 1 A g-1). While the specific capacitance of NGC is steadily higher than that of NGL under all investigated current densities, the capacitance attenuation of NGL is 4.80% from 500 to 10000 cycles showing more durable in cyclicity than that of NGC (8.81%). The two-electrode supercapacitor devices for NGC and NGL exhibit high energy density of 12.21 Wh kg−1 and 9.28 Wh kg−1 at 0.25 A g−1. The difference in electrochemical behaviors between NGC and NGL electrodes can be attributed to the different contribution of nitrogen and oxygenic groups. The buffer agents assisted synthesis procedure coupled with the reasonable capacitance performance suggests an alternative way in the designed functionalization of graphene for developing high performance supercapacitors.

Manipulating structure of graphene and its aggregates has been found to be important for graphene based supercapacitor performance enhancement. However, seldom work has investigated impact of graphene size on its energy storage performance. In this work we have tailored size of graphene oxide from micrometers to tens of nanometers via sonochemical approach. The converted graphene by thermal annealing graphene oxides of different size have been used as electrode materials for constructing supercapacitor with electrolyte of ionic liquid. Electrochemical analysis indicates that there is no obviously positively correlation between energy storage performance and structure characters (specific surface area and electrochemical active edge sites) of graphene, which is contrary to our common knowledge. Based on structure and electrochemical analysis of graphene electrodes, we proposed that reducing the size of graphene results in low edge activity of it for the disrupted aromatic structure on the edges with enriched sp3-carbon defects, where electrical charge is hard to transfer to and through. The practical available area for double layer capacitance setup does not include these electrical charge inaccessible edge regions if the size of graphene is very small. And thus increasing edges of small size graphene has no positive impact on its capacitance enhancement. Furthermore, structure of graphene has shown key influence on equivalent series resistance of bulk electrode. Increased charge transfer frequency between graphene layers of size reduced graphene and higher charge transfer resistance between layers of graphene with increased defective edge were attributed to reduced power density of electrode of graphene with reduced size.

In this paper, a large scale and facile process was proposed for fabricating uniform and cheap Cu/Ag/Ag 3 PO 4 core–shell coaxial nanowires at room temperature. Cu/Ag/Ag 3 PO 4 ternary nanowire photocatalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet–visible diffuse reflectance spectra (DRS). Photocatalytic tests displayed that the Cu/Ag/Ag 3 PO 4 heterostructures possessed a higher degradation rate of methylene blue than pure Ag 3 PO 4 and P25 under visible light irradiation. The enhanced photocatalytic performance could be attributed to effective separation of photogenerated carriers driven by photoinduced potential difference generated at the metal-semiconductor heterojunction interface. Repetitive tests showed that the Cu/Ag/Ag 3 PO 4 heterostructures maintained high stability over 5 cycles. This kind of cheap and high-efficient hybrid photocatalysts are expected to show considerable potential applications in pollution controlling.

Surface defects in relation to surface compositions, morphology, and active sites play crucial roles in photocatalytic activity of graphitic carbon nitride (g-C3N4) material for highly reactive oxygen radicals production. Here, we report a high-efficiency carbon nitride supramolecular hybrid material prepared by patching the surface defects with inorganic clusters. Fe (III) {PO4[WO(O2)2]4} clusters have been noncovalently integrated on surface of g-C3N4, where the surface defects provide accommodation sites for these clusters and driving forces for self-assembly. During photocatalytic process, the activity of supramolecular hybrid is 1.53 times than pure g-C3N4 for the degradation of Rhodamine B (RhB) and 2.26 times for Methyl Orange (MO) under the simulated solar light. Under the mediation of H2O2 (50 mmol L–1), the activity increases to 6.52 times for RhB and 28.3 times for MO. The solid cluster active sites with high specific surface area (SSA) defect surface promoting the kinetics of hydroxide radical...

In this paper, cobalt sulfide (CoS) in-situ hybridized with carbon nanotube (CNT) is achieved through a hydrothermal process with the presence of polyvinylpyrrolidone (PVP). The morphology and structure of CoS/CNT hybrids are investigated by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the product consists of CoS nanoparticles with the diameter of 30–50 nm that well dispersed on the outer surface of CNTs. Furthermore, CoS/CNT hybrid has shown excellent electrochemical capacitance and exhibited favorable electrochemical cycling stability with 93.4% capacitance retention over 1000 cycles. Therefore, the CoS/CNT hybrids can be considered as promising electrode materials for supercapacitor.

It's important to reduce recombination of electrons and holes and enhance charge transfer through fine controlled interfacial structure. In this work, novel graphitic-C3N4 (g-C3N4)/Ag2WO4/Ag ternary photocatalyst has been synthesized by deposition of Ag2WO4 onto g-C3N4 template and followed by sun light reduction of Ag2WO4 into Ag2WO4/Ag. As-prepared g-C3N4/Ag2WO4/Ag presented significantly enhanced photocatalytic performance in degrading methylene blue (MB) under 410 nm LED light irradiation. Metallic Ag0 is used as plasmonic hot spots to generate high energy charge carriers. Optimal g-C3N4 content has been confirmed to be 40 wt%, corresponding to apparent pseudo-first-order rate constant kapp of 0.0298 min−1, which is 3.3 times and 37.3 times more than that of pure g-C3N4 and Ag2WO4, respectively. This novel ternary g-C3N4/Ag2WO4/Ag structure material is an ideal candidate in environmental treatment and purifying applications.

Graphene-based composites have been deemed as promising materials in renewable energy-storage applications. Herein, we report a hybrid architecture consisting of layered molybdenum sulfide nanosheets/N-doped graphene (MoS2/NG) synthesized by one-pot hydrothermal method. By adjusting precursor ratios, flower-like MoS2/NG hybrid with nitrogen content of 3.5 at.% on the graphene layers can be obtained. Electrochemical characterizations indicate that the maximum specific capacitance of the MoS2/NG electrodes reaches up to 245F/g at 0.25A/g (and 146F/g at 20A/g). In addition, the electrode exhibits superior cyclic stability with 91.3% capacitance retention after 1000 cycles at 2A/g. The outstanding performance of the MoS2/NG hybrid benefits from the synergistic effect between the layered MoS2 and N-doped graphene.

In this paper, a facile template-free in situ chemical method has been developed for the synthesis of novel Z-scheme Bi2MoO6/Ag3PO4 composite. The morphology, structure, crystallinity and light absorption wavelength range are investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and UV–vis diffuse reflectance spectroscopy (DRS). The results show that Bi2MoO6 nanoparticles uniformly disperse on the surface of Ag3PO4 photocatalyst. Furthermore, photocatalytic performance of catalysts is evaluated by degrading methylene blue (MB) under 410 nm LED light, and Bi2MoO6/Ag3PO4 composite shows higher photocatalytic activity than Bi2MoO6 and Ag3PO4. Finally, Z-scheme photocatalytic mechanism is discussed.