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Volatile organic compound (VOC) pollution has a serious impact on human and urgently needs to be controlled through the development of new methods and catalytic materials. Compared with traditional thermal catalytic oxidation, the synergistic photothermocatalysis is regarded as a green and environmentally friendly strategy for organic compound pollutant removal, which can promote spontaneous heating of the surface of catalysts to achieve thermal catalytic reaction conditions via harvesting light irradiation. In this paper, a monolithic photothermocatalyst was synthesized through coating graphene oxide (GO) and MnOx in turn on a commercially available melamine sponge, where the GO mainly acted as a photothermal conversion layer to heat the catalytically active MnOx. This monolithic catalyst presented excellent photo-induced activity for formaldehyde elimination under ambient conditions (∼ 90% degradation ratio in 20 min for ∼160 ppm initial concentration formaldehyde), and meanwhile possessed a high catalytic durability for multiple cycles. The kinetic study demonstrated that this photothermocatalytic process followed a pseudo-second-order kinetics. Finally, we proposed a possible formaldehyde degradation pathway based on in situ DRIFTS examination.

Development of efficiently catalytic strategy for oxidative purification of organic pollutants is of great significance. Photocatalysis has become one of the most important technologies in the past half a century, but the inefficiency of photocatalysts drastically suppresses its practical application. This work proposes a synergistic photopiezocatalysis of BiOIO3 under simultaneous photo-irradiation and ultrasound-vibration treatment to degrade various organic pollutants. Different from the high recombination of photo-excited charges in photocatalysis, the ultrasound-induced stress deforms the pyroelectric BiOIO3 to form a piezoelectric potential that drives photo-/thermo-generated free electrons and holes in catalyst to diffuse along opposite directions. In comparison with the single photocatalysis and piezocatalysis, the photopiezocatalysis possesses a synergistic effect, presenting evidently enhanced catalytic performance for decomposing a variety of organic dyes and a persistent organic pollutant 2,4-DCP. No apparent decrease in activity during successive five runs demonstrates that the photopiezocatalysis of BiOIO3 has a high stability and reusability. Finally, a plausible photopiezocatalysis mechanism is proposed based on the determination of active species produced on catalyst and intermediates during pollutant degradation. Our findings provide a new insight to promote charge separation and meanwhile develop an efficient synergistic photopiezocatalysis for environment remediation.

The hydrogen evolution reaction (HER) is a pivotal process for renewable energy storage devices. Improving the intrinsically catalytic activity of earth-abundant metals based electrocatalysts for HER is still a huge challenge. Herein, we put forward a dual phosphorus/sulfur (P/S) doped nickel-cobalt bimetallic material that was grown on nickel foam (Sn-NiCoPx-NF, n = 1–4, NF stands for nickel foam) through a facile one-step phosphorization/sulfuration reaction. Those catalysts represent a novel kind of electrocatalysts with vastly optimized catalytic activity for HER. The S2-NiCoPx/NF with optimal P/S ratio achieves unexpectedly highly efficient catalytic activity for HER in alkaline medium. The overpotential at the current density of 50 mA cm−2 is only 144 mV, which is almost 190 mV less than that of pristine nickel-cobalt bimetallic phosphide catalyst (NiCoPx-NF). In addition, the S2-NiCoPx/NF also has fast reaction kinetics with the smallest Tafel slope of 66 mV/dec and exhibits high stability for HER. This work experimentally demonstrates the advantages of a dual anion modification strategy on improving catalytic activity. Our method offers a new approach to design highly efficient and low-cost electrocatalysts for energy storage and conversion devices.

Mechanical energy harvesting by piezoelectric materials to drive catalysis reactions has recently received extensive attention for fuel production and environmental remediation. It has been well known that some two-dimensional (2D) ultrathin structures which are not piezoelectric in bulk become intrinsically piezoelectric because of the loss of centrosymmetry. In this work, we synthesized a nanosheet-like 2D g-C3N4 catalyst with a thickness of 3–5 nm that showed a significant piezoelectric response. The ultrasound-vibration-induced interior piezoelectric field drove electrons and holes to migrate in opposite directions towards the surface of nanosheets, leading to the formation of active species. This 2D g-C3N4 presented excellent piezocatalytic performance for the degradation of dichlorophenols, and the decomposition efficiency for 2,4-dichlorophenol (2,4-DCP), 2,5-dichlorophenol (2,5-DCP) and 2,6-dichlorophenol (2,6-DCP) reached 98.5%, 85.5%, and 72.1%, respectively, after a 150 min ultrasonic treatment. Furthermore, the good stability and reusability of the 2D g-C3N4 were demonstrated, and a possible degradation pathway was proposed based on the determined intermediates. The findings in this work clearly reveal that the metal-free 2D g-C3N4 should be a promising catalyst to efficiently remove organic pollutants from the environment.

The piezo-electro-chemical effect, a phenomenon of vibration exciting chemical reaction, is hopeful for application in vibration-catalysis but rarely reported. In this work, BaTiO3/g-C3N4 composites are fabricated through a simple mixing-calcining method. The effect is evaluated through the decomposition of Rhodamine B dye under vibration, revealing that the composites exhibit the enhanced vibration-catalytic activity which is 82% compared to pure BaTiO3 which is 57%. The enhancement is attributed to the electric field in the heterojunction effectively separates the vibration-induced carriers and further accelerates carrier migration. Active species are further confirmed on basis of adding the corresponding quencher, in which holes and superoxide radicals are suggested to be the main active species responsible for the dye decomposition, while hydroxyl radicals play a relatively small role. With these advantages, high decomposition ratio, simple preparation method, this heterojunction nano-composite is potential for the decomposition of pollutants.

Manganese oxides (MnOx) are one kind of the most used thermo-catalysts for catalytic oxidation of gaseous organic pollutants, but this process will cause excessive energy consumption. Herein, the photothermal effect of graphene oxide (GO) was utilized to convert the inexpensive solar energy to thermal energy, which subsequently drives the thermo-catalysis of MnOx for degrading gaseous formaldehyde at ambient condition. For achieving high thermal conducting ability, an intimately hybridized 2D/2D composite of GO/MnOx was hydrothermally prepared. Comparing with the GO, the MnOx and the mechanically mixed GO/MnOx, the hydrothermally synthesized composite exhibited significantly improved performance for HCHO removal under the xenon lamp illumination, and the HCHO concentration was rapidly decreased from ∼160 ppm to ∼10 ppm in 20 min. Experimental results using different illumination conditions indicated that the photothermal conversion was mainly from near infrared radiation (NIR). The Mars-van Krevelen mechanism was employed to explain the catalytic process of HCHO removal, where the adsorbed oxygen molecule and lattice oxygen atom were simultaneously activated under irradiation. This work develops an excellent catalyst for effective removal of HCHO, and meanwhile demonstrates that combination of carbonaceous materials with high photothermal conversion capability is a promising strategy to promote the low-temperature catalytic performance of thermo-catalysts.

Nickel hydroxide (Ni(OH)2) has been regarded as a potential candidate for battery-type supercapacitor (BTSC) electrodes, but there is still a challenging task to improve its poor cycling life and low conductivity. In this work, a BTSC positive electrode material of Ni(OH)2/carbon nanosheets (CNS) was prepared during carbonization of the mixture of hydrothermal peach gum and magnesium acetate, followed by the ion-exchange between Ni2+ and Mg2+ in the resultant. The ion-exchange method avoids the high-temperature treatment, and the obtained Ni(OH)2 on CNS has nanosheet-like morphology that possesses abundant active surface, facilitating rapid electrochemical charge/discharge process. More importantly, the coupling of CNS material can improve the electric conductivity and provide developed porosities for electrolyte diffusion. A BTSC device was fabricated using the optimized Ni(OH)2/CNS-4 composite as the positive electrode and the SNACNS reported in our previous work as the negative electrode, which shows satisfactory capacitive behavior (166 C g−1) and capacitance retention of 83.9% over continuous 5000 cycles. In addition, high energy density of 36.9 Wh kg−1 and power density of 400 W kg−1 have been implemented, which is superior to some BTSCs reported previously. Such an attractive performance indicates that Ni(OH)2/CNS-4 composite can be a potential candidate for electrochemical BTSCs.

In this work, the photocatalytic activity of graphitic carbon nitride is improved by co-doping of non-metal elements and morphologic regulation. We introduce B and P elements into the carbon nitride skeleton and meanwhile decrease the thickness by a thermal etching route. The obtained B, P co-doped nanosheets (BPCNNS) has narrow bandgap (2.61 eV) to utilize more visible light, and its ultrathin morphology promotes the separation and migration ability of photo-generated charges. Accordingly, the BPCNNS sample shows enhanced photocatalytic activity for removal of Oxytetracycline (OTC) and Rhodamine B (RhB) in comparison with the un-doped, single element doped and co-doped bulk samples. ∼70% OTC was removed after 120 min and RhB was completely decomposed in 60 min under visible light irradiation by the BPCNNS photocatalyst. Furthermore, the high cycling reusability and stability of the BPCNNS photocatalyst are demonstrated. This work suggests the activity of graphitic carbon nitride can be synergistically enhanced by introducing multiple dopants and morphologic control. Also, it provides a potential photocatalyst to efficiently purify wastewater containing different organic pollutants.

Biomass resources have been regarded as cheap and sustainable precursors to develop functional carbonaceous materials. Herein we report the synthesis of nitrogen doped porous carbon nanosheet material using swelled peach gum as biomass precursor by the KOH activation associated with the chemical blowing of urea. The synergetic effect of swelling and chemical blowing resulted in 2D morphology with an ultrathin thickness, large specific surface area and hierarchical micro/mesoporous structure. The obtained material shows a higher specific capacitance of ∼350 F/g that is much higher than the comparison samples. The assembled aqueous symmetric supercapacitor exhibits a wide voltage window of 0–1.8 V and high energy density of 17.3 Wh/kg at a power density of 450 W/kg. Additionally, good cycling stability of this symmetric cell is demonstrated by the successive 5000 cycles and the 90.3% retention of initial specific capacitance.

The over-use of antibiotics has resulted in seriously environmental pollution. Metal-free photocatalysts have received tremendous attentions due to their environmental friendliness. Meanwhile, morphology and structure of photocatalysts have significant influence on their photocatalytic performance. Herein, we report a metal-free composite photocatalyst of 0-dimensional (0D) graphene quantum dots (GQDs) decorated graphitic carbon nitride nanorods (g-CNNR) that was obtained by a hydrothermal treatment. Characterizations of physicochemical properties demonstrate that this GQDs/g-CNNR photocatalyst has a high crystallization level, enhanced visible light absorption and a staggered band alignment, which can promote the formation, the transportation and the separation of photo-excited electrons and holes. These prominent advantages bring improved photocatalytic activity of the GQDs/g-CNNR for efficient removal of antibiotics. Its photocatalytic reaction rate is 3.46 and 2.03 times higher than those of the pristine graphitic carbon nitride (g-C3N4) and the g-CNNR, respectively. Furthermore, this composite photocatalyst has good application universality for decomposing other antibiotics, and also possesses excellent stability and reusability. We further proved that photo-induced holes and superoxide radicals are main active species in the photocatalytic process. Our findings suggest that efficient g-C3N4 based photocatalysts can be well fabricated by structural regulation of g-C3N4 and formation of tightly contacted interface between g-C3N4 and GQDs.

Amphiphilic carbon-based nanoparticles have recently attracted much attention in stabilizing Pickering emulsions owing to their low cytotoxicity, cost-effectiveness and biocompatibility. In this work, a facile and aqueous synthesis method was developed for the preparation of amphiphilic graphene quantum dots by modifying hydrophilic GQDs (GQDs-COOH) with hydrophobic hexylamine. Distinctive from pristine GQDs-COOH, amphiphilic GQDs show interesting surface-active properties and can stabilize water-in-cyclohexane Pickering emulsions. As efficient particle surfactants, amphiphilic GQDs could be applied in a mini-emulsion polymerization system to synthesize submicron-sized polystyrene particles. Particularly, the as-prepared PS particles were highly luminescent as produced by the highly fluorescent amphiphilic GQDs.

Biomass is regarded as sustainable and low-cost precursors of porous carbons for electrochemical energy storage and conversion due to their varied architecture and plentiful heteroatom containing. We herein developed a hierarchical N-doped porous carbon nanosheet material from soybean milk by employing simultaneous hard-template and KOH activation strategy. Hard-template of CaCO3 nanospheres, KOH activation and the melt template of potassium species respectively result in the formation of macropores, micropores and nanosheet-like morphology. Moreover, abundant nitrogen and oxygen elements in precursor bring a high heteroatom percentage in resultants, which don’t contribute psuedocapacitance but also promote electron transfer and conductivity. The obtained carbons exhibit good charge storage capacity with a specific capacitance of 240.7 F g−1 (1 A g−1) and the excellent retention of initial specific capacitance (92.2% to 20 A g−1) that is much higher than those of biomass-based porous carbons. A symmetric all-solid-state supercapacitor using KOH/PVA as electrolyte has a specific capacitance of 149.3 F g−1 (0.5 A g−1), and good cycling stability with capacitance retention of 89.3% after 5000 cycles. The device displays energy density of 10.2 Wh kg−1 at a power density of 351 W kg−1, and retains 8.2 Wh kg−1 even at a high power density of 19,600 W kg−1 with a wide voltage window of 1.4 V.

Phase-boundary catalysis on the liquid–liquid biphasic interface has great potential in various applications due to the advantages of the energy-saving, possibly organic solvent-free process and post-synthesis treatment of products and catalysts. Notwithstanding significant development in visible-light-driven photocatalysis for energy and the environment, the application of graphitic carbon nitride (g-C3N4) in organic synthesis is limited because of its poor dispersibility in organic solvents. Herein, we report amphiphilic two-dimensional g-C3N4 nanosheets (CNNS) with two hydrophilic/hydrophobic functionalities synthesized by soft-chemical exfoliation and covalent modification with the 4-(trifluoromethyl)benzyl (TFMB) group. As a phase-boundary photocatalyst, these amphiphilic CNNS on the oil–water biphasic interface can drive the photocatalytic reduction of nitrobenzene to aniline without any external stirring. Impressively, easy extraction of the synthesized aniline by the water phase favors product separation. Such an amphiphilic CNNS photocatalyst also shows good performance for different organic solvents or even solvent-free systems, multiple reuses, and nitrobenzene compounds substituted with various groups, indicating an innovative application for organic synthesis.

Crab shells derived from discarded seafood bio-waste, are a naturally abundant and sustainable resource, but their difficult solubility limits their processing and applications, resulting in severe environmental pollution. It is very attractive to discover approaches for reducing the threats of crab shells to the environment and even to convert crab shells into useful materials. Herein, we attempted to convert crab shells into three-dimensional (3D) honeycomb-like graphitized hierarchically porous carbons (GHPCs) by a convenient one-step carbonization process simultaneously combining catalytic graphitization and chemical activation routes. The removal of abundant inorganics from crab shells resulted in a unique honeycomb-like structure, and meanwhile a high doping concentration of N element was inherited in the framework of GHPCs. Furthermore, the simultaneous activation/graphitization treatment developed interconnected hierarchical porosity with a large accessible surface area and highly graphitized skeleton. Benefiting from these unique structural characteristics, GHPCs exhibited a remarkable capacitive performance as supercapacitor electrodes. The GHPC electrode delivered a high gravimetric capacitance of 367.4 F g−1 at 1 A g−1 in 6 M KOH electrolyte. More importantly, the electrode showed satisfactory rate capability where an extremely high current density of 100 A g−1 for charge–discharge operation was available in both KOH and Na2SO4 electrolytes. Furthermore, the assembled symmetric flexible all-solid-state capacitor exhibited a high energy density of 11.1 W h kg−1 and a power density of 100.5 W kg−1, as well as a good cycling stability of 90.8% capacitance retention after 10 000 cycles in a PVA/KOH gel electrolyte. Our approach not only relieved the environmental pollution caused by crab shells but also achieved the production of a high-performance supercapacitor electrode, which was promising for industrial energy conversion and storage. It therefore demonstrated an example of trash-to-treasure transformation.

As an indispensable chemical, ammonia is produced by the Haber–Bosch process using H2 and N2 under severe reaction conditions. Recently, photocatalysis using solar energy has been regarded as a promising technology to fix N2 under mild conditions. However, compared to other photocatalytic applications, photocatalytic N2 fixation suffers from low efficiency because of the difficulties associated with N2 adsorption and activation on the photocatalyst surface, as well as the instability of active sites on the photocatalyst. Herein, we covalently grafted an ethylenediaminetetraacetic acid (EDTA) motif onto graphitic carbon nitride nanosheets (CNNS) by a high-temperature dehydration reaction, and subsequently chelated Fe3+ ions to obtain highly dispersive and stable Fe3+ sites on CNNS. Compared with the un-modified sample, the obtained Fe-EDTA–CNNS has improved visible light absorption and high charge separation and transfer ability. Impressively, a much higher activity for N2 fixation (50 μmol L−1 h−1) than those of the comparative materials and photocatalysts in the literature as well was achieved by the Fe-EDTA–CNNS. Experimental and calculation results demonstrate that the modification of CNNS with an Fe-EDTA unit enhances the reduction ability of photo-generated electrons and decreases the N2 adsorption energy. More importantly, the Fe-EDTA unit with an electron-withdrawing effect can accumulate photo-excited electrons and then activate the adsorbed N2 molecules. Additionally, the strong chelating action results in a relatively high stability for the Fe-EDTA–CNNS photocatalyst. This work not only develops a potential photocatalyst for efficient ammonia production, but also provides a facile surface modification strategy to construct active sites and regulate the charge transfer route on photocatalysts.

Great advances in photocatalysis have been made by developing various efficient photocatalysts, but investigation on practical applications of photocatalysis is relatively backward. Herein we report a facile surface modification approach to functionalize textiles with excellent ability for photocatalytic self-cleaning and degradation of indoor volatile organic pollutants. Graphitic carbon nitride nanosheets (CNNS) in colloidal suspension were directly sprayed onto the surface of cellulose fibers in textiles, and the powerful hydrogen bonding action between surface hydroxyl groups of cellulose and plentiful hydroxyl and amino groups of exfoliated CNNS from alkali-treating realizes high stability of CNNS modified textiles. Due to ultrathin 2D thickness and high visible light transparency, the modification of CNNS would not affect the hand feeling of textiles and shield their original colors. The obtained textiles show superior photocatalytic self-cleaning performance to remove stains from various colored pollutants under solar light irradiation, including industrial organic dyes and juices. Meanwhile, gaseous formaldehyde also can be efficiently decomposed using Xe lamp or commercial LED lamp as light sources. This work realizes photocatalytic performance of textiles using a simple spraying method, and it has great potential application in textile self-cleaning, not only for surface stains but also for volatile organic compounds from textile release.

For most graphene electrodes, there is usually a disappointing trade-off relationship between gravimetric and volumetric capacitive characteristics, which is definitely a major stumbling block in the development of real-life supercapacitors with high energy density. Herein, we rationally designed a hierarchically porous and modestly packed diamine pillared graphene, which is achieved by a facile and straightforward reaction between commercialized bulk graphite fluoride and in situ generated diamine anions. Combined reliable characterization studies demonstrate that an advantageous reductive defluorination of the unsubstituted carbon–fluorine units (C–Fx) accompanies the foreseen substitution of C–Fx by diamines, endowing the resultant products with recovered 2D π-conjugation and high conductivity. In comparison to ethylenediamine and p-phenylenediamine, pseudocapacitive 4,4′-oxydianiline (ODA) molecular pillars, having a bulky and rigid geometry, provide the ODA-G product with a greatly widened d-spacing (6.2 A), large wettable and electrolyte-accessible specific surface area (1985 m2 g−1), hierarchically porous and interconnected structuration, heavyweight nature (density of 1.08 g cm−3), etc. Consequently, the symmetric supercapacitor fabricated using ODA-G as both electrodes delivers an impressive gravimetric capacitance of 328.5 F g−1 and a maximized volumetric capacitance of 354.8 F cm−3 at a current density of 0.5 A g−1, whilst exhibiting a remarkable rate capability and cycling stability. Apart from an exceptional gravimetric energy density, the volumetric energy density of the ODA-G device is as high as 19.5 W h L−1 at a large power density of 9093 W L−1. It is notable that this contribution deepens our insight into the chemistry of graphite fluoride, and can guide the judicious design and synthesis of versatile functionalized graphene applicable to other electrochemical energy-storage systems, or the newly-emerging photothermal water evaporation, desalination, etc.

As a metal-free visible light photocatalyst, the photocatalytic performance of graphitic carbon nitride (g-C3N4) is limited. To improve the activity of g-C3N4, we herein report a binary S, B co-doped g-C3N4 (SBCN) by thermally treating the precursor mixture of thiourea, melamine and boron oxide. Characterization results show the obtained SBCN has ultrathin sheet-like morphology and these doped heteroatoms are uniform distributed in the sample. Compared to the pristine g-C3N4, the SBCN has a small band gap with additional absorption in visible light region, decreased photoluminescence emission and electric resistance and enhanced photocurrent response. These advantages endue SBCN with excellent photocatalytic activity for degradation of organic dyes, and its reaction rate is 6.5 times higher than that of the g-C3N4. Moreover, the successive cycles demonstrate that this SBCN possesses a superior stability and reusability. Finally, we propose a possible photocatalytic mechanism based on the band structure and mainly active species.

Mechanical energy as the green and sustainable energy source widely distributes in natural environment. In this paper, we successfully realize the conversion of mechanical energy through a friction route on the tribocatalyst of Bi2WO6. Under magnetic stirring, the friction between the PTFE-sealed magnetic bar and the catalyst particles resulted in the electron transfer crossing the contact interface, in which PTFE accepted the electrons and simultaneously the holes were left on the catalyst. The positively charged catalyst was demonstrated through electrostatic attraction and repulsion tests. Like photocatalytic process, the holes on the valence band of Bi2WO6 have strong oxidative ability that can efficiently oxidize organic pollutants. The tribocatalytic tests showed that the Bi2WO6 could eliminate organic dyes under magnetic stirring in dark, and we could further optimize the tribocatalytic performance via regulating the size of magnetic bar and reactor material. Finally, a high stability of tribocatalysis was revealed by the multiple tests. This work not only develops a green tribocatalysis strategy to oxidative purification of organic pollutants, but also provides a possible pathway to convert mechanical energy in environment to chemical energy, such as potential applications in environmental remediation and sustainable energy.

Graphitic carbon nitride (g-C3N4) has been proved to be a potential photocatalyst for environment purification, but the high recombination rate of photogenerated carriers leads to the low photocatalytic efficiency. Herein, we report the enhanced degradation of chlorophenols by 2D ultrathin g-C3N4 nanosheets with intrinsic piezoelectricity through photopiezocatalysis strategy. Under the simultaneous visible-light irradiation and ultrasonic vibration, the 2D g-C3N4 presented improved removal efficiency for elimination of 2,4-dichlorophenol (2,4-DCP) with an apparent rate constant of 6.65 × 10−2 min−1, which was 6.7 and 2.2 times of the photocatalysis and piezocatalysis, respectively. The improved removal efficiency was attributed to the sufficient separation of free charges driven by the ultrasound-induced piezoelectric field in the 2D g-C3N4, which was demonstrated by the enhanced current response under photopiezocatalysis mode. Additionally, the photopiezocatalysis of 2D g-C3N4 was proved to possess well universality for removing different chlorophenols, as well as high durability and dechlorination efficiency. Finally, a possible photopiezocatalytic mechanism for removal of 2,4-DCP was proposed based on the electron paramagnetic resonance (EPR) technique and the determination of intermediates through liquid chromatography-mass spectrometry (LC-MS) analysis. This work provides a promising strategy for the design of energy-conversion materials towards capturing solar and mechanical energy in ambient environment.

Graphitic carbon nitride (g-C3N4) as a metal-free polymer semiconductor has received extensive attentions, but its application was drastically suppressed due to low photocatalytic activity. Herein, non-metal heteroatom co-doping is employed to extend the visible light absorption, and regulating morphology into nanosheets promotes the charge separation and transfer. Elements of P/S were successfully introduced into the carbon nitride framework by thermal condensation of their corresponding precursors with melamine. And, the presence of NH4Cl would produce abundant gas to blow CN layers separately to form thin nanosheets. The obtained P/S co-doped carbon nitride nanosheet (g-PSCNNS) sample presents enhanced absorption in visible light region and efficiencies for separation and transport of photo-generated charges. The synergistic effect of elemental co-doping and nanosheet-like morphology endues g-PSCNNS with superior photocatalytic performance for removal of organic pollutants in comparison with the pristine, P or S individual doped and P/S co-doped g-C3N4 samples. Moreover, this g-PSCNNS sample has excellent photocatalytic stability and reusability. Experiments of radical quenching demonstrate superoxide radical is the main active species in the photocatalytic process.

The high aspect-ratio morphology of two-dimensional (2D) nanostructures endues them with distinct advantages for photocatalytic or photoelectrical applications. Although various attempts have been devoted to the liquid exfoliation of graphitic carbon nitride (g-C3N4) to obtain ultrathin nanosheets (CNNSs), the high exfoliation efficiency, well preservation of in-planar structure and facile operation cannot be simultaneously realized. Furthermore, functionalization of CNNSs is highly desired to promote the capability of photoabsorption, charge separation and transfer. Herein, we one-step prepared well-dispersed graphene quantum dots (GQDs)-modified CNNSs (GQDs/CNNSs) colloids via a facile and efficient GQDs-assisted exfoliation approach in a normal ultrasonic water bath. The exfoliation procedure was optimized by tuning the dopant in GQDs, ultrasonic time and GQDs dosage. The obtained colloidal GQDs/CNNSs show a typical 2D morphology with lateral size of several 100 nm and ultrathin thickness of 1.5–1.8 nm. What is more, we can tailor the semiconductive behavior of GQDs by heteroatom doping and achieve a p–n-type P-doped GQDs-modified CNNSs colloids. This p–n GQDs/CNNSs material presents the enhanced separation efficiency of photoexcited carriers and photocatalytic activity in comparison with bulky g-C3N4 (CN) and other CNNSs materials from acid or alkali exfoliation.

A facile one-step approach was employed to synthesize oxygen-rich porous carbon nanosheets (OPCNs) using glucose as carbon source via Mg2(OH)2CO3 simultaneously chemical blowing and activation. Besides the simple synthetic process, the OPCNs material has an ultrathin thickness about 10–20 nm, numerous heteroatoms, developed porosity and good electrical transport properties. The electrochemical tests demonstrated that OPCNs possessed high specific capacitance, good rate performance and low intrinsic resistance. Moreover, the comparison experiments indicated that the specific capacitance of OPCNs was higher than those of carbon materials prepared by the activation of KOH and ZnCl2, chemical blowing of NH4Cl and melamine, and the MgO template route under the similar synthetic conditions. The assembled symmetric OPCNs-based supercapacitor showed a maximum energy density of 8.2 Wh kg−1 at a power density of 450 W kg−1 within a voltage range of 0–1.8 V in 0.5 M Na2SO4 aqueous electrolyte. Additionally, the cycle test over 10,000 runs suggested that this supercapacitor had good cyclic performance.

Nitrogen-doped porous carbon has aroused extensive interests owing to its unique physical and chemical properties. However, the complicated nitrogen-doping method and high cost limit its practical application. In this work, the nitrogen-rich biomass soybean was used as a single precursor for both carbon and nitrogen source to prepare nitrogen-doped hierarchical micro-mesoporous carbon via templating carbonization coupling with subsequent KOH activation. The influence of KOH dosage on the morphology, structure and electrochemical performance (supercapacitor and oxygen reduction reaction (ORR)) was studied in detail. The optimized ANPC-3, synthesized under the KOH/carbon mass ratio of 3/1, possesses high specific surface area of 1749 m 2 g −1 , developed hierarchical micro-mesoporous structures as well as moderate nitrogen content (1.37 at.%). ANPC-3 exhibits a large energy density of 12.5 Wh kg −1 at a power density of 450 W kg −1 with excellent charge-discharge cyclic stability of 96.5% capacitance remaining after 5000 cycles. As an ORR electrocatalyst, it shows improved ORR activity as well as much better stability and methanol-tolerance capacity than commercial Pt/C catalyst. The unique hierarchical micro-mesoporous textures, high surface area and moderate N-doping level make biomass-derived ANPC-3 become an excellent electrode material in various applications.

Simple anti-counterfeiting printing using biocompatible, non-toxic and highly efficient luminescent materials plays crucial roles in economic and social fields as well as in our daily lives. In this work, new nitrogen doped graphene quantum dots (N-GQDs) are synthesized and applied in the preparation of quick-dry fluorescent ink for both writing and printing. The N-GQDs are synthesized based on a one-step bottom-up molecular fusion between 1,3,6-trinitropyrene and triethylamine by a solvothermal process with a high yield of 84.6%. Triethylamine simultaneously acts as a reaction medium and a nitrogen-doping agent for the formation of fluorescent N-GQDs. The as-prepared N-GQDs exhibit a single-layer graphene structure, high crystallinity, uniform size and excitation-independent fluorescence emission with a narrow half-peak width (66 nm). Successful doping of N atom in GQDs enables bright blue fluorescence with a high absolute photoluminescence quantum yield (17.8%). Owing to their excellent photostability and good solubility in ethanol, N-GQDs are applied to easily prepare quick-dry fluorescent ink for both writing and printing by simply blending GQDs with glycerol in an ethanol medium. Moreover, synthesis of a fluorescent powder and hydrogel is also achieved.

Inspired by the distinct advantages of BiOCl(001) ultrathin nanosheets being rich in oxygen vacancies (VO) and metal nanoparticles (NPs) with unique surface activity for the adsorption-activation of alcohols, metal-decorated BiOCl(001) ultrathin nanosheets were expected to exhibit enhanced photocatalysis for the selective oxidation of aromatic alcohols. Herein, a small quantity (1.5 wt%) of Au and Pd NPs were loaded on ultrathin BiOCl(001) nanosheets by photodeposition to obtain Au–BiOCl and Pd–BiOCl photocatalysts, respectively. Among the various photocatalysts including BiOCl ultrathin nanosheets, light-irradiated BiOCl ultrathin nanosheets, and metal-decorated BiOCl ultrathin nanosheets, the Pd–BiOCl sample displayed the highest photocatalytic activity for the oxidation of aromatic alcohols to the corresponding aldehydes under ambient conditions. According to a series of experimental analyses as well as the insights from the calculations, the enhanced photocatalysis of Pd–BiOCl was attributed to the remarkable interface cooperation by the electronic coupling between Pd and the BiOCl(001) surface, where the abundant VO sites of BiOCl(001) ultrathin nanosheets and the surface activity of Pd NPs synergistically promote the adsorption-activation of O2 and alcohol molecules as well as facilitating the separation and transfer of photogenerated carriers. These findings highlight the synergistic effect of the metal–semiconductor interface on the photocatalytic oxidation of organic compounds and shed some light on the rational design of highly efficient photocatalysts for selective conversion processes with environmentally benign oxidants like O2.

Graphene quantum dots (GQDs) as new 0-dimensional (0D) materials have exhibited promising applications in numerous fields, and these enormous potentials are largely dependent on their electronic properties. Herein we tailored the semiconductive behavior of GQDs and transformed the n-type hydrothermally synthesized GQDs to p-type via the modification of P═O groups with an electron-withdrawing ability. The obtained highly dispersed and stable P-doped GQDs (P-GQDs) had uniform size and thickness, high crystallinity, and wide visible-light absorption region. The subsequent assembly with the n-type graphitic carbon nitride (CN) formed a stable metal-free photocatalyst because of the π–π interaction between conjugated GQDs sheets and CN layers and the possible hydrogen bonds as well. Due to the formation of p–n junction on the P-GQDs/CN interface, the photogenerated charges were efficiently separated which resulted in an enhanced photocatalytic performance. This strategy illuminates the GQDs applications by con...

A facile one-step approach was employed to synthesize porous g-C 3 N 4 flake (PCNF) via thermally polymerizing melamine with the presence of MgCO 3 template. CO 2 gas released from the decomposition of MgCO 3 prohibited the further polymerization of CN framework and separated the CN layers to produce a flake-like morphology, and meanwhile the removal of MgO nanoparticles resulted in a porous structure. The resultant PCNF exhibited enhanced visible-light photocatalytic activity for degrading organic dyes, and its rate constant is ∼4 times higher than that of bulky CN. What is more, this material presented an excellent stability and superior universality for various pollutants.

Titania nanosheets (TNSs) were of importance for photocatalytic application due to the unique two-dimensional (2D) morphology, high crystallinity and plentiful surface charge. However, the large bandgap prohibited the efficient utilization of sun light. Herein, we employed graphene quantum dots (GQDs) as green photocatalytic promoter to decorate TNSs during the electrostatic flocculation. The obtained GQDs/TNSs heterojunction was systematically characterized, and the results demonstrated that the composite exhibited an intimate coupling of GQDs and TNSs, a markedly visible light absorption and therefore the enhanced separation efficiency of photogenerated charges. This composite photocatalyst showed the enhanced photocatalytic performance for the photodegradation of Rhodamine B (RhB) under visible light irradiation in comparison with pure restacked TNSs and GQDs. Furthermore, this composite exhibited a superior reusability, and a high degradation ratio about 90 % was still achieved in the 5th cycle. Moreover, a possible mechanism was proposed and superoxide radicals, holes and hydroxyl radicals were determined as the active species.

In this paper, we reported a new and environment-friendly strategy to exfoliate graphitic carbon nitride (CN) in hot water to obtain ultrathin CN nanosheets (CNNS). By thermal treating, water molecules were intercalated into the interlayer space of bulky CN and further hydrolyzed the bridge-linked N groups between tri-s-triazine units, thereby cutting the CN layers into CNNS. Due to the negative charges on surface (Zeta potential was −13 mV at pH 7), the CNNS colloids were extremely stable. The physicochemical characterization indicated that the as-prepared CNNS had a typical 2D morphology with a ~1.2 nm thickness and numerous –OH groups on surface. Moreover, the high charge separation and transport ability were achieved in CNNS because of the retaining of conjugated CN system. Compared to the bulk CN, the as-prepared ultrathin CNNS exhibited an enhanced photocatalytic performance (four times higher than that of the bulk CN) for degradation of organic dye under visible light irradiation. Additionally, the superior reusability and the excellent generality of CNNS for decomposing other pollutants were also demonstrated. Finally, we proposed a possible mechanism of CNNS based on the examined band structure and the main active species determined by quenching of various active species.

The efficient utilization of natural biomass as renewable raw materials is of importance. We herein prepared porous carbon fibers (PCFs) by activation of the extracted cellulose microfibers from the agriculture byproduct of corn straw. Different from the porous carbons (PCs) by directly activating straw, the obtained PCFs had typical one-dimensional morphology with high surface area (2013 m2 g−1) and large pore volume (1.27 cm3 g−1). The influence of the ZnCl2/cellulose mass ratio on the electrochemical performance was studied, and the optimized PCF(1:1) possessed a much higher specific capacitance than the PC(1:1) sample, which was attributed to the improved specific surface area as well as the fiber-like morphology where it had short ion diffusion route and small interfacial resistance in comparison to PCs. PCFs have a high specific capacitance of 230 F g−1 at 0.5 A g−1, and 183 F g−1 was retained at 20 A g−1 (79.6%), revealing an excellent rate capability. The assembled symmetrical supercapacitor exhibited a wide potential window of 1.8 V, small electrochemical impedance, and superior cycle performance. Moreover, a high energy density of 16.0 Wh kg−1 was obtained at a power density of 450.4 W kg−1, which was preserved of 6.9 Wh kg−1 at a high power density of 14,194.3 W kg−1.

Well-controlled mesoporosity is of importance for porous carbons as electrochemical electrode materials. However, the ordered mesoporous carbons prepared from the template approaches face the fact of relative low specific surface area in comparison to activated carbons. Herein, we employed a hard-template route associated with the chemical activation to prepare N-doped mesoporous carbon by co-casting of carbon and nitrogen precursors into the pore channels of mesoporous silica. The obtained activated N-doped mesoporous carbon (ANMC) material preserved the morphology and mesoporous structure of template, and meanwhile a secondary mesoporosity was introduced by the KOH activation. It was demonstrated that the dominant porosity in ANMC sample was from mesopore, and it possessed a high mesopore surface area (2505.6 m2 g−1) and mesopore volume (1.74 cm3 g−1). The N dopant was determined to be pyridinic-N, pyrrolic-N, quaternary-N and pyridine-N-oxide, which did not only contribute the pseudocapaticance but also facilitated the electron transfer in the carbon skeleton. The developed mesoporosity and N doping made this material exhibit superior electrochemical performance that was much higher than those of ordered mesoporous carbon, N-doped ordered mesoporous carbon and activated N-doped carbon samples. Also, the specific capacitance 336.9 F g−1 (0.5 A g−1) and the rate capability were higher than those of other reported mesoporous carbons. In addition, the assembled symmetrical supercapaictor simultaneously showed the high energy density and power density, as well as presented the superb cycling ability (∼98.5% capacitance retaining after 5000 runs).

The dehydrogenation properties of commercial NaAlH 4 ball milled with a NiFe 2 O 4 nanoparticle catalyst have rarely been studied. In this work, temperature programmed desorption analysis indicates that the onset temperature of three dehydrogenation steps of NaAlH 4 + 3 mol% NiFe 2 O 4 is 72, 132 and 82 °C lower than those of as-milled NaAlH 4 , respectively. The dehydrogenation capacity of NaAlH 4 could be significantly improved by adding NiFe 2 O 4 . Furthermore, NaAlH 4 + 3 mol% NiFe 2 O 4 displays good cycle stability at 150 °C and only a slight capacity loss after five cycles. The apparent activation energies of NaAlH 4 + 3 mol% NiFe 2 O 4 for the three dehydrogenation steps are 54.3, 73.1 and 113.1 kJ mol −1 , respectively, as determined by differential scanning calorimetry and Kissinger analysis. From the analysis of X-ray diffraction, the new phases after dehydrogenation are NaFeO 2 and Al 3 Ni. The reaction between NiFe 2 O 4 and NaAlH 4 during desorption is revealed.

In this paper, we reported a novel biomass-derived porous carbon from torreya grandis shell for the first time by means of carbonization and KOH activation under N2. The pore structures were related to the ratio of KOH and activation temperature. N2 adsorption-desorption tests indicated that the sample of AC-800-3 has a maximum specific surface area of 2100.8 m2 g−1 and proper pore volume of 1.02 cm3 g−1. The electrode prepared with AC-800-3 realized a high capacitance of 290.5 F g−1 at 0.5 A g−1 and excellent rate capability of 62.6% in three-electrode system. The assembled symmetrical cell of AC-800-3 electrode exhibited a high energy density of 13.5 W h kg−1 at a power density of 360.1 W kg−1 in the potential range of 0–1.6 V and excellent cycling stability with 93.1% retention of the initial capacitance after 5000 cycles.

Herein, graphitic carbon nitride (g-C 3 N 4 ) as a novel thermo-driven catalyst was used for catalytic decomposition of organic dyes with the assistance of H 2 O 2 . In comparison with the experiment with individual catalyst or H 2 O 2 , a prominent enhancement of performance was achieved by the synergetic effect of g-C 3 N 4 and H 2 O 2 . Experimental parameters like the H 2 O 2 dosage and reaction temperature were optimized, and the catalyst exhibited excellent application universality for various concentration and different dyes. By physicochemical characterizations, the modification or doping with oxygen-containing groups on carbon nitride framework was demonstrated. We proposed a possible mechanism that the doping level trapped thermo-excited electrons to promote the separation of electrons and holes. On the other hand H 2 O 2 was reduced by the excited electron to produce hydroxyl radical. The quenching experiment suggested the holes and hydroxyl radical were the main active species, thus verifying the synergetic effect of g-C 3 N 4 and H 2 O 2 . Additionally, the superior stability and reusability were also proved by the successive five cycles, where the activity was even gradually improved with the increase of cycle number.

Herein, we reported the synthesis of nitrogen-rich graphitic carbon nitride nanosheets (NRCNNS) material by an NH4Cl assisted chemical blowing approach, where the released gas from the decomposition of NH4Cl prohibited the further polymerization of CN framework and separated the CN layers. A typical two-dimensional morphology with high aspect-ratio was demonstrated by scanning electron microscopy and transmission electron microscopy observation, and the excess amino group on the skeleton was proved by Fourier transform infrared and X-ray photoelectron spectra technologies. Different from the spectral blue-shift in other carbon nitride nanosheets, an enhanced absorption in visible light region was achieved in our NRCNNS due to the N,O-doping level in the band gap. The optimal NRCNNS material with an NH4Cl/melamine mass ratio of 4.0 exhibited a promoted activity (5 times higher than that of the bulky carbon nitride) and reusability for degradation of organic dye under visible light irradiation. Moreover, a possible mechanism was proposed based on the results of valence band spectra and the quenching experiments of active species.

Photocatalysis technology has stimulated extensive research interest in various fields, but several limitations, such as the inefficient separation ratio of photo-generated charges and the possible release of metal ions from metal oxides or sulfides, need to be overcome before its practical application. Herein, we fabricated a metal-free carbonaceous composite photocatalyst via modification of 2D polymeric carbon nitride (PCN) with 0D graphene quantum dots (GQDs) by an ultrasound-assisted route. Characterization results clearly indicated the formation of 0D/2D composite structure with an intimately contacted interface, and the type II band structure promotes the charge separation between PCN and GQDs. As a result, an enhanced photocatalytic activity for degradation of dyes was achieved by the GQDs/PCN in comparison to the single PCN and GQDs. Furthermore, multiple cycling tests reflected the GQDs/PCN had relatively high photocatalytic durability. This study provides a facile method to construct carbonaceous composite and demonstrates it is a promising photocatalyst for environmental remediation.

A direct solid state Z-scheme photocatalytic system was fabricated by assembling two-dimensional (2D) g-C3N4 nanosheets (CNNS) and titania nanosheets (TNS), which were obtained from the delamination of their corresponding layered precursors. By introducing TNS, the interlayer restacking of CNNS was effectively prohibited, forming uniform CNNS/TNS composites. The tightly contacted CNNS/TNS interface promoted the charge transfer and therefore improved the separation ratio of photogenerated electron-hole pairs. The photocatalytic performance of CNNS/TNS in various mass ratios was investigated for dye degradation, and the degradation rate of optimal sample 0.7CNNS/0.3TNS was 2.34 and 48.5 times higher than those of proton flocculated pure CNNS and TNS, respectively. Superoxide radicals and hydroxyl radicals were determined as the main active species by the quenching experiment. Moreover, the enhanced generation of superoxide radicals and hydroxyl radicals was confirmed by the absorption spectra of nitroblue tetrazolium and the photoluminescence spectra of 2-hydroxy terephthalic acid, respectively. Finally, we proposed a possible Z-scheme mechanism based on the theoretical calculation and the experimental results.

N-doped activated carbon sheets (NACS) have been successfully synthesized using glucose as carbon source via melamine-assisted chemical blowing and sequent KOH-activation method. The obtained carbon material possesses a sheet-like morphology with ultrathin thickness, hierarchical micro/mesoporous structure, high specific surface area (up to 1997.5 m 2 g −1 ) and high pore volume (0.94 cm 3 g −1 ). Besides, NACS material with a nitrogen content of 3.06 wt% presents a maximum specific capacitance of 312 F g −1 at a current density of 0.5 A g −1 in 6 M KOH aqueous electrolyte due to the cocontribution of double layer capacitance and pseudocapacitance. It also displays good rate performance (246 F g −1 at 30 A g −1 ) and cycle stability (∼91.3% retention after 4000 galvanostatic charge-discharge cycles). The assembled NACS-based symmetric capacitor exhibits a maximum energy density of 20.2 Wh kg −1 at a power density of 448 W kg −1 within a voltage range of 0–1.8 V in 0.5 M Na 2 SO 4 aqueous electrolyte. Thus, the unique porous sheet structure and nitrogen-doping characteristic endue the electrode material a potential application for high-performance supercapacitors.

The use of activated porous carbons in supercapacitors is of increasing interest as a result of their superior porosity and facile preparation. However, their porous structure is strongly dependent on the activation procedure. We report here an air-assisted approach to activate a spherical resorcinol–formaldehyde resin to obtain porous carbons without the use of an inert atmosphere or chemical activating agent. The porous structures of the obtained activated carbon spheres (AACSs) were related to the activation time and the percentage of mesopores gradually increased as the activation time increased to 6 h. The sample activated for 6 h (AACS-6) had the largest pore volume (1.01 cm g−1) and the highest Brunauer–Emmett–Teller surface area of 2178 m2 g−1. The optimum electrochemical performance was realized on an AACS-6 electrode that had a large specific capacitance of 222 F g−1 at 0.5 A g−1 in a three-electrode system. A slight decrease in capacitance (12.5%) was obtained as the current density increased to 20 A g−1, indicating the significant rate capability. The AACS-6 electrode showed excellent cycling stability with a ∼97% retention of the initial capacitance after 5000 cycles. The assembled symmetrical cell based on the AACS-6 electrode had a high energy density of 10.1 W h kg−1 at a power density of 398.7 W kg−1 in the potential range of 0–1.6 V in a 0.5 M Na2SO4 aqueous electrolyte.

Herein, we report the preparation of a ternary photocatalyst by assembling graphitic carbon nitride nanosheets (CNNS) and reduced graphene oxide (rGO) with two-dimensional nature, along with crystalline cadmium sulfide (CdS). The high visible light absorption and the gradient band structure of the ternary photocatalyst promoted the photo-generation of charges and the followed separation of electrons and holes on different compositions. This ternary composite photocatalyst exhibited enhanced photocatalytic performance for the photodegradation of Rhodamine B (RhB) under visible light irradiation in comparison with the single phase as well as their dual composites. Furthermore, this composite showed a superior reusability, and a high degradation ratio > 90% was still achieved in the 5th cycle. Moreover, a possible mechanism was proposed and superoxide radicals were determined as the main active species.

PDA nanoaggregates can be formed at ultra-high concentrations of dopamine (DA, 8 mg mL−1), promoting application of DA/PDA chemistry in material modification; however, polydopamine (PDA) film also is formed at such concentrations. To achieve a high density of PDA nanoaggregates on the material surface at low concentrations of DA, here, a simple strategy was developed and a novel superhydrophobic/superoleophilic sponge with outstanding adsorbency and flame-retardancy was fabricated. Two-step DA oxidative self-polymerization in different media was applied. After the raw melamine sponge (ME) was first coated with PDA film at 0.5 mg mL−1 of DA in mild buffer (Tris–HCl, pH 8.5), the resulting PDA film was then applied as “solid reagent” and contributed to formation of a high density of PDA nanoaggregates at 3.0 mg mL−1 of DA in a harsh medium (water/ethanol/ammonium). Covalent grafting of n-dodecylthiol (DT, low surface energy molecular) onto PDA nanoaggregates was combined in the second step using the reactivity of PDA. As investigated by scanning electron microscopy (SEM), the as-prepared ME/PDA/DT sponge has a 3D hierarchical structure with a high density of nanoaggregates on an interconnected porous sponge network. The size and density of PDA nanoaggregates on the sponge could be easily controlled by adjusting the concentration of ammonia in the second step. The ME/PDA/DT sponge was superhydrophobic (water contact angle of 161.5°) and superoleophilic (oil contact angle of 0°). Owing to the high loading of nanoaggregates, highly porous structure, and superhydrophobic property, the ME/PDA/DT sponge possessed outstanding adsorption properties towards oil and organic solvents, including high adsorption capacity (weight gains ranged from 6632% to 15112%), fast adsorption kinetics (reaching adsorption capacity in 30 seconds), and good reusability (no obvious decrease of adsorption capacity after ten adsorption/distillation cycles). The ME/PDA/DT sponge exhibited improved flame-retardancy compared with the raw melamine sponge, indicating significant potential for oil adsorption and organic solvent clean-up with low risk of fire and explosion.

Activated ordered mesoporous carbon (AOMC) material was prepared by a one-step carbonization/activation method using SBA-15 as hard template, furfuryl alchohol (FA) as carbon source and ZnCl 2 as activation agent. The as-synthesized AOMC possesses hierarchical micro/mesoporous structure and high BET surface area (up to 1465.7 m 2 g − 1 ), which accelerate the ion-transport and charge-transfer during charging/discharging process for supercapacitors. A maximum specific capacitance value of 270 F g − 1 for AOMC electrode at a current density of 1 A g − 1 in 6 M KOH aqueous solution was obtained from the charge–discharge curves. Meanwhile, it also exhibited outstanding rate performance (~ 80% capacity retention from 0.5 A g − 1 to 20 A g − 1 ) and excellent cycling stability (∼ 94% retention after 5000 continuous charge–discharge cycles). The assembled AOMC-based symmetric cell delivers a maximum energy density of 11.8 Wh kg − 1 at a power density of 450.1 W kg − 1 under a voltage range of 0–1.8 V in 0.5 M Na 2 SO 4 aqueous electrolyte.

In order to improve the gaseous and electrochemical hydrogen storage kinetics of the Mg2Nitype alloy, the elements Cu and Nd were added in the alloy. The nanocrystalline and amorphous Mg2Ni-type alloys with the composition of (Mg24Ni10Cu2)100-xNdx (x = 0, 5, 10, 15, 20) were prepared by melt spinning technology. The effects of Nd content on the structures and hydrogen storage kinetics of the alloys were investigated. The characterization by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) reveals that all the as-cast alloys hold multiphase structures, containing Mg2Ni-type major phase as well as some secondary phases Mg6Ni, Nd5Mg41, and NdNi, whose amounts clearly grow with increasing Nd content. Furthermore, the as-spun Nd-free alloy displays an entire nanocrystalline structure, whereas the as-spun Nd-added alloys hold a mixed structure of nanocrystalline and amorphous structure and the amorphization degree of the alloys visibly increases with the rising of the Nd content, suggesting that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. The measurement of the hydrogen storage kinetics indicates that the addition of Nd significantly improves the gaseous and electrochemical hydrogen storage kinetics of the alloys. The addition of Nd enhances the diffusion ability of hydrogen atoms in the alloy, but it impairs the charge-transfer reaction on the surface of the alloy electrode, which makes the high rate discharge ability (HRD) of the alloy electrode first mount up and then go down with the growing of Nd content.

Thermocatalysis and photocatalysis have been widely investigated to removal of volatile organic compounds (VOCs). However, thermocatalysis needs high-temperature to activate oxygen species, therefore resulting in additional energy consumption. Meanwhile, photocatalysis suffers the rapid charge recombination and the slow surface process. Herein, we combined thermocatalysis and photocatalysis into a free-standing composite film catalyst that was prepared through a facile filtration method using two-dimensional graphene oxide (GO), manganese oxide (MnOx) and polymeric carbon nitride (CN) nanosheets as building blocks. The superior photothermal effect of GO rapidly enhanced the film temperature to ~85 °C, and then initiated the MnOx thermocatalysis. Furthermore, the increased temperature also promoted the charge diffusion and the surface reaction process of CN photocatalyst. Impressively, with the synergetic photothermocatalysis and photocatalysis, this composite film catalyst presented improved performance for catalytic oxidation of gaseous formaldehyde at ambient condition under xenon light irradiation, compared with the individual thermocatalyst and photocatalyst, as well as the photothermocatalyst. In addition, cycling experiments demonstrated the film catalyst possessed good durability. This investigation associates photothermocatalysis with photocatalysis for improving formaldehyde catalytic degradation, hopefully providing a new and efficient strategy not only for VOCs removal, but also for other catalytic applications.

Biomass precursors with natural porous structure and multifarious heteroatoms are desirably sustainable precursors for synthesis of carbon materials for energy and environmental applications. Herein, we reported wax gourd based porous carbons (WGPCs) with developed micro/mesoporous structures via potassium hydroxide (KOH) chemical activation. The optimized material that is denoted as WGPC-4 exhibits high specific surface area (2919 m2 g−1) with oxygen and nitrogen contents of 17.9 at.% and 1.0 at.%, respectively. In a three-electrode system, the WGPC-4 electrode presents high specific capacitance of 333 F g−1 at current density of 1 A g−1. Meanwhile, the assembled symmetrical cell using aqueous electrolyte (0.5 M Na2SO4) has high specific capacitance (167 F g−1 at 1 A g−1), stable cycling characteristics (93% capacitance retaining after 5000 runs) and excellent energy density of 19.2 Wh kg−1. Furthermore, these WGPC-4 electrodes were assembled into an all-solid-state supercapacitor using KOH/polyvinyl alcohol (PVA) gel as solid electrolyte, whose specific capacitance is 258 F g−1 at 1 A g−1, retention at the 2500th run is 87% and energy density is 13.0 Wh kg−1 under a high power density. These materials with excellent structural characteristics are an ideal candidate for high-performance supercapacitors.

Bismuth oxybromide (BiOBr) has been proved to be a potential photocatalyst for removal of organic pollutants, but the insufficient separation of photo-generated electrons and holes results in its low photocatalytic activity. In this work, we utilized the piezoelectric-like behavior of BiOBr to suppress the recombination of photo-excited charges. Under the excitation of the piezo-vibration and the irradiation using a 9 W white LED, the BiOBr catalyst shows a high reaction rate for catalytically decomposing organic dyes, which is 5.62 and 11.0 times of those from the individual photocatalysis and piezocatalysis, respectively. This catalyst has high structural stability and can be recycled for reuse, as well as presents good activity for degrading different organic pollutants via the synergetic photocatalysis/piezocatalysis process. On the basis of the piezoelectric-like effect and our experimental results, a possible catalytic mechanism has been proposed considering the separation of photo-induced charges and the formation of highly active radicals. This work associates photocatalysis with piezoelectric-like effect for improving the catalytic performance of BiOBr, hopefully providing a new and efficient approach not only for wastewater treatment, but also for other catalytic applications.

Porous electrode materials with large surface area and suitable pore size, as well as short diffusion distance of electrolyte ions in pore channels are desiderated for supercapacitor applications. Herein, we reported the synthesis of mesoporous activated carbon spheres (MACSs) that were obtained by the activation of resorcinol-formaldehyde (RF) resin using ZnCl2 as the activating agent. The spherical mor- phology of MACSs was characterized by scanning electron microscopy and transmission electron microscopy observa- tions, and the well-developed mesoporous network (∼2.73 nm), high BET specific surface area (up to 2437.1 m 2 g −1 ), and total pore volume (1.37 cm 3 g −1 )w ere obtained by a nitrogen sorption technique. Electrochemical measurements showed the excellent capacitive performance of MACSs and small internal resistance. It presented maxi- mum specific capacitance value of 204 F g −1 for MACS-8 in 2 M KOH aqueous solution at a current density of 0.5 A g −1 and still remained 126 F g −1 at large current density as 20 A g −1 , which well met the practical requirements of supercapacitors. Besides, the electrode material also demon- strated prominent long-cycling stability without any capacity loss after 5000 cycles.

A novel graphitized porous carbon nanosphere (GPCNS) material obtained by a convenient simultaneous activation and graphitization route, which was realized by heating resorcinol–formaldehyde (RF) resin nanospheres immersed with ZnCl2 and FeCl3 in an inert atmosphere, has been reported. A high graphitization level was achieved through the catalytic graphitization by reduced Fe metal, and the hierarchically micro/mesoporous structure was produced in a controlled fashion by tuning the mass ratio of the activating agent ZnCl2 and a carbon precursor. An optimal sample of GPCNS-2 was prepared with a FeCl3/ZnCl2/RF mass ratio of 0.5 : 2 : 1, exhibiting a highly graphitized framework and uniform spherical morphology with an average diameter of ∼500 nm, as well as well-interconnected micro/mesoporous structure with a large surface area of 1664.8 m2 g−1. Acting as an electrode material for a supercapacitor application in 6 M KOH electrolyte, GPCNS-2 displayed excellent electrochemical performance with a high specific capacitance of 402.5 F g−1 at a current density of 1 A g−1. Moreover, an electrochemical impedance spectroscopy test demonstrated that the low internal electrical resistance of GPCNS-2 contributed a superior rate capability of above 75% retention rate even at 50 A g−1. Furthermore, the GPCNS-2 electrode possessed an outstanding cycling stability, and about 96% of its initial specific capacitance at 5 A g−1 was maintained after 5000 cycles.

This paper describes the preparation of graphitic porous carbon spheres (GPCS) from spherical resorcinol/formaldehyde resin by Fe-catalysis at 900 °C. The GPCS were characterized by their highly graphitized structures, uniform spherical morphology with an average diameter of ∼450 nm, pore size of 1–4 nm and relatively large surface area of ∼1100 m2 g−1. Their electrochemical performance was studied using cyclic voltammetry and galvanostatic charge–discharge measurements, and the results showed an enhanced charge storage capacity, with a specific capacitance of 127.4 F g−1 in 2 M KOH at a current density of 0.2 A g−1 that was nearly 3 times larger than that of amorphous porous carbon spheres. Moreover, electrochemical impedance spectroscopy tests demonstrated the low electrical resistance and ion transfer resistance of the GPCS, which resulted in the high retention of specific capacitance at a 10 A g−1 current density. The recycling experiments indicated their superior stability, and 96% of their initial specific capacitance was maintained after 5000 cycles.