[en] Controllable synthesis of nanocarbons with tunable morphologies from sustainable biomass through facile one-step route for ionic liquid based supercapacitors with high energy density and high power characteristics is of great interest but remains an ongoing challenge. Herein, we report the design and synthesis of nanocarbons with tunable morphologies (i.e., honeycomb-like porous carbons, carbon nanosheets and irregular-shaped carbon microparticles) from sustainable pine barks through reliable one-step chemical activation process. We found that the honeycomb-like porous carbons can be produced via direct KOH activation while the uniform carbon nanosheets were obtained by employing magnesium powder as the reactive self-sacrificing template. These three samples have different morphologies and textural properties render them totally disparate electrochemical performance in ionic liquid electrolyte. Benefiting from its distinct structural advantages, the as-obtained porous carbon nanosheets has excellent electrochemical capacitive performance including large specific capacitance (193 F/g at 1 A/g), superior rate capability (superior specific capacitance retention of 69.4% at 40 A/g), good cycling stability (good capacitance retention after 8000 cycles) and integrated high energy density& high power characteristics (excellent energy density of 55.8 Wh/kg even at an ultrahigh power density of 39.375 kW/kg). We believed that this work reported here not only provides a versatile strategy towards nanocarbons with tunable morphologies from sustainable biomass but also sheds some new light to efficiently regulate the morphologies of nanocarbons for electrochemical energy storage applications.

[en] Highlights: • Damming effect on C emission and storage was studied in a tributary of the Three Gorges Reservoir. • Damming resulted in higher TOC, CH₄ and CO₂ concentrations in upstream sediments. • CH₄ emissions downstream estuary were slightly lower than upstream during high reservoir levels. • CH₄ emissions prevailed by ebullition particularly at the estuary during low reservoir levels. River damming has seen a growing trend in demand worldwide and the impounded reaches are considered hotspots of greenhouse gas emissions. However, it remains unclear how the spatial distribution of C-gas in sediments and methane (CH₄) emissions of dammed tributary changes under different operation periods of the Three Gorges reservoir (TGR). We measured CH₄ and carbon dioxide (CO₂) concentrations in sediment and CH₄ emissions from a dammed river of the TGR, and evaluated the effect of damming on the spatial variability of carbon in the sediment and on CH₄ flux. It was found that damming led to a distinct spatial pattern of total organic carbon (TOC) in the sediment, which resulted in higher CH₄ and CO₂ in upstream sediment compared to the downstream. During the TGR impounding period, the upstream CH₄ diffusive flux (0.253–0.427 mg m⁻² h⁻¹) across the water-air interface was higher than in the downstream (0.093 mg m⁻² h⁻¹), which was consistent with the spatial variation of CH₄ in the sediments. However, the CH₄ emission was predominantly by ebullition and the flux in the downstream (169.173 mg m⁻² h⁻¹) was significantly higher than upstream (12.23–123.05 mg m⁻² h⁻¹) in the discharging period. This can be attributed to a sharp increase in TOC in downstream sediment due to riparian zone soil erosion on both banks, which was caused by periodic large fluctuation in the water level, and a shallow water depth in the downstream. This study adds to our understanding of effects of the TGR's operation on CH₄ emissions from a dammed tributary and suggests that the water level fluctuation of tributaries which has direct influence on ebullition and methane oxidation caused by manipulation of the TGR should not be overlooked.

[en] Transition metal element doping into semiconducting materials has been a promising method for the preparation of active photocatalysts for the efficient use of solar energy. In this study, we report the facile synthesis of Fe doped SrWO₄ nanoparticles by a solvothermal method for photocatalytic nitrogen reduction. The intrinsic bandgap of SrWO₄ is greatly narrowed by the Fe-dopant which not only extends the light absorption from UV to visible light range, but also reduces the charge recombination. The narrowed band structure still fulfils the thermodynamic requirements of nitrogen reduction reaction. At optimal doping concentration, Fe doped SrWO₄ shows much higher photocatalytic nitrogen fixation performance. The present study provides a route toward the development of active photocatalysts for nitrogen fixation. (paper)

[en] To investigate the effect of pre-strain on behaviors in a specially developed Al-4.5Zn-1.2Mg alloy, transmission electron microscopy (TEM) bright field (BF) imaging combined with select area electron diffraction (SAED), Vickers-hardness tests and electrical conductivity tests was conducted for insight into precipitation in aluminum (Al) matrix during two step ageing, and standard exfoliation corrosion (EXCO) test combined with high-angle angular dark field scanning transmission electron microscopy (HAADF-STEM) and scanning electron microscopy (SEM) was carried out for corrosion behavior. Results showed that pre-strain accelerated precipitation during two step ageing as the sequence of: (i) supersaturated solid solution (SSS), GPI zones precipitations, GPI dissolution; (ii) SSS, fcc precipitates, η’ phases or η phases. And the precipitation hardening of the fcc precipitates was not effective as GPI zones. Pre-strain also accelerated EXCO developing, which was mainly attributed to the coverage ratio of η phases on high-angle grain boundaries (HAGBs) increasing as pre-strain increase. (paper)

[en] Graphical abstract: The novel 3D flowerlike nanomaterial demonstrates high capacitive property on energy storage application. -- Highlights: • 3D conducting polymer are firstly reported as supercapacitor electrode materials. • 3D flowerlike morphology is favorable for electrons and ions transport. • 3D flowerlike PEDOT/MnO₂ manifests much better cycle durability. • Sythesis approach of PEDOT/MnO₂ may give rise to 3D new materials. • Quite small size MnO₂ nanoparticles are well dispersed on conducting matrix. -- Abstract: The electrochemical performances of 3D flowerlike PEDOT are characterized by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. It shows high specific capacitance of 111 F g⁻¹, which is greatly higher than that of 1D PEDOT nanofibers we reported before. In addition, on the basis of this PEDOT matrix, 3D flowerlike PEDOT/MnO₂ composite is synthesized by a two-step approach as a high-property supercapacitor electrode material. Scanning and transmission electron microscopy show that 3D PEDOT matrix is kept well and decorated well by MnO₂ nanoparticles (2–5 nm). And the capacitive performances are tested as well. The specific capacitance of this composite can highly reach around 183 F g⁻¹, and retain more than 90% of the original value after 1000 consecutive charge/discharge cycles. These results indicate that the 3D flowerlike PEDOT/MnO₂ composite possesses a synergy effect of complementary properties of both components, which results in higher specific capacitance and better stability

[en] Graphical abstract: The homogeneously grafted PEDOT/MWCNTs containing numerous whorl fingerprint-like open ends endows with excellent electrochemical performances. Highlights: ► A ternary phase system with the surfactant AOT is utilized to efficiently solve the problem of the aggregation of MWCNTs. ► The homogenously grafted PEDOT/MWCNTs composite is synthesized by in situ chemical polymerization in the ternary phase system. ► The core–shell nanotubes contain many whorl fingerprint-like open ends that are greatly favorable for the transportation of the electrons and ions. ► The energy density of grafted PEDOT/MWCNTs has been enhanced by a factor of four comparing to that of native MWCNTs. ► The grafted PEDOT/MWCNTs composite manifests better cycle durability than both the constituents. - Abstract: The homogenously grafted composite of poly (3,4-ethylenedioxythiophene)/multiwalled carbon nanotubes (PEDOT/MWCNTs) is synthesized by in situ chemical polymerization in a ternary phase system. When carbon nanotubes are dispersed in this system containing sodium bis(2-ethylhexyl) sulfosuccinate (AOT), the surfactant AOT can efficiently hinter the aggregation of MWCNTs by absorbing and arranging regularly on the MWCNT surface. It is greatly advantageous to the stabilization of MWCNTs, which leads to the equally grafted composite. Its morphology was observed by scanning and transmission electron microscopes. Especially, the core–shell nanotubes contain many whorl fingerprint-like open ends that are efficiently favorable for the transportation of the electrons and ions. Such grafted PEDOT/MWCNTs composite nanotubes manifest enhanced electrochemical performances. We investigate the application of PEDOT/MWCNTs as a high-property supercapacitor and test its capacitive performance by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The energy density of grafted composite, 11.3 Wh kg⁻¹, has been enhanced by a factor of four comparing to that of native MWCNTs. Besides, the composite also presents better cycle durability after 1000 cycles. This composite will be a good candidate for the applications on supercapacitors.

[en] Highlights: • Bioinspired Fe doped SrMoO₄ photocatalyst is prepared by a facile solvothermal method. • The bandgap and light absorption of SrMoO₄ can be tuned by changing the doping concentration. • Fe doping can balance the defects and photocatalytic activity of nitrogen reduction. -- Abstract: Photocatalytic nitrogen reduction reaction (NRR) for the green synthesis of ammonia is a promising alternative way to the energy-intensive Haber-Bosch process. In this study, we report Fe doped SrMoO₄ by a solvothermal method for solar nitrogen reduction. It is found that Fe doping significantly changes the intrinsic bandgap of SrMoO₄ and extends the light absorption from UV light to visible light region. At optimal doping concentration, the Fe doped SrMoO₄ shows enhanced photocatalytic nitrogen reduction performance compared to the pristine SrMoO₄ in ultrapure water. The enhancement is ascribed to the optimized defect states, newly formed Fe–Mo active centers, and extended light absorption range. The characterization results show that Fe doping with optimal concentration not only prohibits the fast recombination of photoinduced charge carriers, but also promotes the interfacial charge transfer. The narrowed intrinsic bandgap enables the Fe doped SrMoO₄ to absorb more solar light while keeps the thermodynamic activity to nitrogen reduction with appropriate band energetics. The present study provides an effective strategy for the design of active nitrogen fixation photocatalysts.

[en] Highlights: • The introduction of carbon black has solved the problem of Fermi-level misalignment. • Carbon black supplies conductive pathways to activate more amount of PEDOT. • The active charge of PEDOT is investigated by Scanning Kelvin Probe. • Corrosion protection is achieved by the coating with the optimal concentration of carbon black. • The delamination inhibition is due to the active polarization of the interface. - Abstract: The application of conducting polymers on zinc tends to result in an electronically highly insulating interface leading even to Fermi-level misalignment at the polymer/metal interface. This makes the conducting polymers electrochemically inactive. To prevent this Fermi-level misalignment, carbon black was introduced as conductive spacer between the conducting polymer and the zinc into composite coatings of poly (3,4-ethylenedioxythiophene) (PEDOT) nanoparticles and a polyvinyl butyral (PVB) binder. It was found that the carbon black not only enabled electronic contact between zinc and the PEDOT, but also increased the amount of electrochemical available PEDOT in the coating, by supplying the necessary conductive pathways