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In this work, poly(vinylidene fluoride‐hexafluoropropylene) (PVDF‐HFP)/mesoporous graphitic carbon nitride (mpg‐C3N4) composite fiber web have been prepared and characterized for photocatalytic methylene blue (MB) degradation and sensing applications. The electrospinning technique, operating at a flow rate of 1 mL/h and a voltage of 15 kV, was utilized to prepare the composite membranes of PVDF‐HFP with the uniform distribution of the mpg‐C3N4. The composite web demonstrated outstanding photocatalytic activity for the degradation of MB, reaching a quick 68% drop in MB concentration in just 45 min. The composite web furthermore worked as a sensor for MB detection. After MB exposure, the film resistance was increased, suggesting its potential as a chemiresistive sensor. The maximum resistivity of PVDF‐HFP/mpg‐C3N4 composites was found to be 90 Ω·m at 2% concentration of MB. The MB molecules' adsorption on the surface of the composite web and the existence of photocatalytic byproducts on the surface may be responsible for this shift in resistance. This dual functionality highlights the adaptability and potential of the PVDF‐HFP/mpg‐C3N4 composite web as a versatile material for environmental sensing and cleanup. This research presents a comprehensive approach to the synthesis, characterization, and evaluation of such flexible membranes for potential applications as self‐cleaning devices and chemiresistive sensor. Highlights: PVDF‐HFP/mpg‐C3N4 composite membranes act as an efficient material for MB degradation (68%) with visible light exposure.mpg‐C3N4 plays the role of active material in degradation.PVDF‐HFP/mpg‐C3N4 composite membrane also act as sensors for MB detection.Composite membrane becomes chemiresistive due to notable resistivity changes with MB concentration. [ABSTRACT FROM AUTHOR]

A catalyst system with dedicated selectivity toward a single hydrocarbon or oxygenate product is essential to enable the industrial application of electrochemical conversion of CO2 to high-value chemicals. Cu is the only known metal catalyst that can convert CO2 to high-order hydrocarbons and oxygenates. However, the Cu-based catalysts suffer from diverse selectivity. Here, we report that the functionalized graphene quantum dots can direct CO2 to CH4 conversion with simultaneous high selectivity and production rate. The electron-donating groups facilitate the yield of CH4 from CO2 electro-reduction while electron-withdrawing groups suppress CO2 electro-reduction. The yield of CH4 on electron-donating group functionalized graphene quantum dots is positively correlated to the electron-donating ability and content of electron-donating group. The graphene quantum dots functionalized by either –OH or –NH2 functional group could achieve Faradaic efficiency of 70.0% for CH4 at −200 mA cm−2 partial current density of CH4. The superior yield of CH4 on electron-donating group- over the electron-withdrawing group-functionalized graphene quantum dots possibly originates from the maintenance of higher charge density of potential active sites (neighboring C or N) and the interaction between the electron-donating group and key intermediates. This work provides insight into the design of active carbon catalysts at the molecular scale for the CO2 electro-reduction. Electrochemical conversion of CO2 to fuels is a promising strategy to reduce the ever-increasing CO2 emission. Here, the authors developed graphene quantum dots (GQDs) catalysts to efficiently convert CO2 to CH4 and revealed the significance of electron-donating functional groups in regulating the reactivity of GQDs. [ABSTRACT FROM AUTHOR]

Elemental doping is an effective approach to modify the local electronic structure of active sites. Herein, we tailored tin electrocatalysts with boron doping to tune and stabilize the valence state of Sn. The initial screening in the flow cell with 1 M KOH showed that the boron-doped Sn (Sn(B)) exhibited both higher formate production efficiency and rate than the pristine Sn particles in CO2 electroreduction. The optimal Sn(B) catalyst was translated to a solid-state electrolyzer incorporating solid electrolyte (either H+ or OH− solid conductor). The H+ solid conductor enabled direct production of formic acid, however, it sacrificed the anodic energy efficiency compared to formate production in the OH− solid conductor. H+ conductor cell produced a Faradic efficiency for formic acid of 88% with energy efficiency of 41% at cell voltage of 3.0 V and partial current density of 60.3 mA cm−2 . Whereas, the Faradic efficiency of formate reached 87% at partial current density of 83 mA cm−2 and cell voltage of only 2.5 V at which the full-cell energy efficiency was attained 50% in the OH− conductor cell. [ABSTRACT FROM AUTHOR]

Astounding graphitic carbon nitride (g-C3N4) nanostructures have attracted huge attention due to their unique electronic structures, suitable band gap, and thermal and chemical stability, and are insinuating as a promising candidate for photocatalytic and energy harvesting applications. The growth of a free-standing film is desirable for widespread electronic devices and electrochemical applications. Here, we present a facile approach to prepare free-standing films (15 mm × 10 mm × 0.5 mm) comprising g-C3N4 nanolayers by the pyrolysis of dicyandiamide (C2H4N4) utilizing the chemical vapor deposition (CVD) technique. The synthesis is done under low-pressure conditions of argon (∼3 Torr) and at a temperature of 600 °C. The as-synthesized g-C3N4 films are systematically studied for their structural/microstructural characterization using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and UV-visible spectroscopy techniques. The excitation-dependent photoluminescence (PL) spectra of the as-synthesized g-C3N4 film exhibited an intense, stable and broad emission peak in the visible region at ∼459 nm. The emission spectra of free-standing g-C3N4 films show a blue shift and band sharpening compared to that of the g-C3N4 powder. [ABSTRACT FROM AUTHOR]

The significance of graphene and its two-dimensional (2D) analogous inorganic layered materials especially as hexagonal boron nitride (h-BN) and molybdenum disulphide (MoS2) for "clean energy" applications became apparent over the last few years due to their extraordinary properties. In this review article we study the current progress and selected challenges in the syntheses of graphene, h-BN and MoS2 including energy storage applications as supercapacitors and batteries. Various substrates/catalysts (metals/insulator/semiconducting) have been used to obtain graphene, h-BN and MoS2 using different kinds of precursors. The most widespread methods for synthesis of graphene, h-BN and MoS2 layers are chemical vapor deposition (CVD), plasma-enhanced CVD, hydro/solvothermal methods, liquid phase exfoliation, physical methods etc. Current research has shown that graphene, h-BN and MoS2 layered materials modified with metal oxide can have an insightful influence on the performance of energy storage devices as supercapacitors and batteries. This review article also contains the discussion on the opportunities and perspectives of these materials (graphene, h-BN and MoS2) in the energy storage fields. We expect that this written review article including recent research on energy storage will help in generating new insights for further development and practical applications of graphene, h-BN and MoS2 layers based materials. [ABSTRACT FROM AUTHOR]