The role of microbial electrogenesis in regulating methane and nitrous oxide emissions from constructed wetland-microbial fuel cell

This study assesses a sustainable solution to greenhouse gases (GHGs) mitigation using constructed wetland-microbial fuel cells (CW-MFC). Roots of wetland plant Acorus Calamus L. are placed in biological anode to better enable anode microorganisms to obtain rhizosphere secretion for power improvement. Three selected cathode materials have a large difference in GHG emissions, and among them, carbon fiber felt (CFF) shows the lowest emissions of methane and nitrous oxide, which are 0.77 ± 0.04 mg/(m²·h) and 130.78 ± 13.08 μg/(m²·h), respectively. The CFF CW-MFC achieves the maximum power density of 2.99 W/m³. As the influent pH value is adjusted from acidic to alkaline, the GHGs emissions are reduced. The addition of Ni inhibits GHGs emission but decreases the electricity, the power density is reduced to 1.09 W/m³, and the methane and nitrous oxide emission fluxes decline to 0.20 ± 0.04 mg/(m²·h) and 15.49 ± 1.86 μg/(m²·h), respectively. Low C/N ratio reduces methane emission, while high C/N ratio effectively inhibits nitrous oxide emission. At the influent pH 8 and C/N = 5:1, the methane emission flux is approximately 10.60 ± 0.27 mg/(m²·h), and the nitrous oxide emission flux is only 10.90 ± 1.10 μg/(m²·h). Based on the above experimental results by controlling variable factors, it is proposed that CW-MFC offers an environment-friendly solution to regulate GHG emissions.     

Additive manufacturing,quasi-static and dynamic compressive behaviours of ceramic lattice structures

Ceramic lattice structures (CLSs) are used for construction in common and extreme environments because of the extraordinary properties of ceramics. In this study, we designed and additively manufactured CLSs with distinct structural parameters to explore their quasi-static and dynamic compressive behaviours in detail. It was demonstrated that both the relative density (?ρ) and inclination angle (ω) had a significant impact on the quasi-static and dynamic mechanical properties of the CLSs. Furthermore, the mathematical relationships between the quasi-static compressive properties, including quasi-static compressive strength (QS), quasi-static Young’s modulus (QY), and quasi-static energy absorption (QE), versus ?ρ and ω obeyed the Gibson–Ashby and Deshpande and Fleck models, respectively. It was revealed by experiment and simulation that as the stiffness increased, the quasi-static failure mode of the CLSs changed from a parallel-vertical-inclined mixed mode to a parallel-vertical mode. In addition, the relationship between the dynamic mechanical properties of the CLSs versus ?ρ and ω also followed the Gibson–Ashby and Deshpande and Fleck models. The exceptional dynamic increase factor indicated that CLSs are highly suitable for extreme environments. These findings will aid in the research and development of customised additively manufactured CLSs.     

Some studies on reducing carbon dioxide emission from a CRDI engine with hydrogen and a carbon capture system

The increased use of fossil fuels in the transportation sector has led to an exponential rise of carbon dioxide in the atmosphere. The carbon dioxide (CO₂) is the major cause of global warming resulting in climate change and extreme weather conditions. This study explores the ways of reducing the CO₂ emission from the exhaust of a common rail engine. The reduction in CO₂ emissions were achieved by a combination of methods. It includes the use of low carbon biofuels (cedarwood oil (CWO), and wintergreen oil (WGO)), induction of zero-carbon, hydrogen in the intake manifold and a zeolite-based after-treatment system. In diesel, CWO and WGO were blended 20% by volume and experiments were conducted at different load conditions. The results shows that 20% blending of winter green oil resulted in maximum CO₂ reduction of 20% as compared to diesel. The emission was further reduced with the induction of hydrogen along with the after-treatment system. It is seen that a maximum of 54% reduction in CO₂ emission could be achieved with the combination for WGO in comparison to diesel without much affecting the other emissions and performance parameters.     

Effect of interface types on the heat-resistance of Cansas-II SiCf /SiC composites

The heat-resistance of the Cansas-II SiC/CVI-SiC mini-composites with a PyC and BN interface was studied in detail. The interfacial shear strength of the SiC/PyC/SiC mini-composites decreased from 15 MPa to 3 MPa after the heat treatment at 1500 °C for 50 h, while that of the SiC/BN/SiC mini-composites decreased from 248 MPa to 1 MPa, which could be mainly attributed to the improvement of the crystallization degree of the interface and the decomposition of the matrix. Aside from the above reasons, the larger declined fraction of the interfacial shear strength of the SiC/BN/SiC mini-composites might also be related to the gaps in the BN interface induced by the volatilization of B₂O₃·SiO₂ phase, leading to a significant larger declined fraction of the tensile strength of the SiC/BN/SiC mini-composites due to the obvious expansion of the critical flaws on the fiber surface. Therefore, compared with the CVI BN interface, the CVI PyC interface has better heat-resistance at high temperatures up to 1500 °C due to the fewer impurities in PyC.     

High Q×f values of Zn-Ni co-modified LiMg0.9Zn0.1-xNixPO4 microwave dielectric ceramics for 5G/6G LTCC modules

In this work, Zn-Ni co-modified LiMg_0.9Zn_0.1-xNi_xPO₄ (x = 0–0.1) microwave dielectric ceramics were fabricated using a solid state synthesis route. Rietveld refinement of the XRD data revealed that all ceramic samples have formed a single phase with olivine structure. SEM images showed that the samples have a dense microstructure, that agrees with the measured relative density of 97.73 %. Based on the complex chemical bond theory, Raman and infrared reflectance spectra, we postulate that ε_r is mainly affected by the ionic polarizability, lattice and bond energy, while P-O bond plays a decisive role in Q×f and τ_f value. Optimum properties of Q×f ~ 153,500 GHz, ε_r ~ 7.13 and τ_f ~ ?59 ppm/°C were achieved for the composition LiMg_0.9Zn_0.06Ni_0.04PO₄ sintered at 875 ℃ for 2 h. This set of properties makes these ceramics an excellent candidate for LTCC, wave-guide filters and antennas for 5 G/6 G communication applications.     

Fabrication of NixCo3-xS4 hollow nanosphere as wideband electromagnetic absorber at thin matched thickness

Nowadays, transition metal sulfide (TMS), especially for spinel crystal structure (A_xB_3-xS₄), have been proved to be a promising electromagnetic (EM) absorber if been used to deal with the severe electromagnetic pollution. However, EM performance degradation and absorption layer thickness-decreasing at present remains a big challenge, owning to the poor EM attenuation ability. To overcome this barrier, herein we reported a Ni_xCo_3-xS₄ (x = 0, 0.3, 0.6, 1.0) absorber with hollow sphere structure to realize a good EM performance with a thinner matched thickness (<1.5 mm). The average sizes of these Ni_xCo_3-xS₄ distributed in 450–550 nm. The dielectric loss ability (ε'') can be boosted by tuning the molar ratio of Ni/Co, which attributes to EM performance. Additionally, hollow structure would lead to the electromagnetic multi-reflection, also benefited to EM performance. The results demonstrated that the maximum qualified absorption bandwidth (f_E) of 3.8 GHz can be achieved for the Ni_0·3Co_2·7S₄ sample when specimen thickness only equals to 1.3 mm.     

Dual functions of three-dimensional hierarchical architecture on improving the rate capability and cycle performance of LiNi0.8Co0.1Mn0.1O2 cathode material for lithium-ion battery

The main obstacles in lithium-ion battery are limited by rate performance and the rapid capacity fading of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811). Herein, a novel three-dimensional (3D) hierarchical coating material has been fabricated by in situ growing carbon nanotubes (CNTs) on the surfaces of Ni–Al double oxide (Ni–Al-LDO) sheets (named as LDO&CNT) with Ni–Al double hydroxide (Ni–Al-LDH) as both the substrate and catalyst precursor. The resultant LDO&CNT nanocomposites are uniformly coated on the surfaces of NCM811 by the physical mixing method. The rate capability of the resultant cathode material retains to 78.80% at a current rate of 3C. Its capacity retention increases by 6.7–14.42% compared with pristine NCM811 after 100 cycles within a potential range of 2.75–4.3 V at 0.5C. The improved rate capability and cycle performance of NCM811 are assigned to the synergistic effects between Ni–Al-LDO and CNTs. The hierarchical LDO&CNT nanocomposites coating on the surface of NCM811 avoids the aggregation of conductive CNTs and the stacking of Ni–Al-LDO nanosheets. Furthermore, it accelerates Li⁺ and electrons shuttle and reduces the reaction of Li₂O with H₂O and CO₂ in air, which results in Li₂CO₃ and LiOH alkali formation on the NCM811 surface.     

Methane bi-reforming over boron-doped Ni/SBA-15 catalyst: Longevity evaluation

A highly active and stable boron-promoted catalyst was successfully prepared by using the sequential incipient wetness impregnation technique and examined for methane bi-reforming reaction. The initial investigation found that the NiO and B₂O₃ particles were dispersed on the outer surface of the high surface area SBA-15 support. In addition, the catalytic activity was increased linearly with the tested reaction temperature due to the endothermic nature of the reaction. In fact, the catalyst achieved the CH₄ conversion and H₂/CO molar ratio of approximately 67.3% and 2.7, respectively at 1073 K. The resulting product ratio is highly suitable for downstream Fischer-Tropsch (FT) synthesis. The B-promoted catalyst showed the lowest degree of catalyst deactivation (4%) at 1023 K. Additionally, the XPS measurements unveiled that the boron facilitates the adsorption of CO₂ by donating electrons to the neighbouring Ni cluster and thus improved its catalytic performance. Furthermore, Raman and XRD analysis revealed that the boron promotion on 10%Ni/SBA-15 could prevent the reoxidation and deposition of carbonaceous species.     

Effect of preparation method on physicochemical properties and catalytic performances of LaCoO_3 perovskite for CO oxidation

Perovskite oxides LaCoO_3 prepared by templating, co-precipitation and sol-gel method with different complexants were systematically characterized and its catalytic performances for CO oxidation were investigated. The samples were characterized by X-ray diffraction, thermogravimetry analysis and differential scanning calorimetry, N_2 physisorption, transmission electron microscopy, temperature program reduction of hydrogen, temperature program desorption of oxygen and X-ray photoelectron spectroscopy measurement, results of which show that the properties of LaCoO_3, such as surface morphology, surface area, surface compositions, redox capability, oxygen vacancy, as well as the calcination temperature and formation mechanism, depend intimately on the preparation method. Catalytic tests indicate that the sample prepared by carbon templating method shows the best activity for CO oxidation, with full CO conversion obtained at 135 ℃. In particular, the catalyst can be activated and significant increase of activity can be obtained with the increase of reaction time. The cyclic and longterm stability of catalysts were discussed and compared.     

Hydrogen from wet air and sunlight in a tandem photoelectrochemical cell

A solid-state photoelectrochemical (SSPEC) cell is an attractive approach for solar water splitting, especially when it comes to monolithic device design. In a SSPEC cell the electrodes distance is minimized, while the use of polymer-based membranes alleviates the need for liquid electrolytes, and at the same time they can separate the anode from the cathode. In this work, we have made and tested, firstly, a SSPEC cell with a Pt/C electrocatalyst as the cathode electrode, under purely gaseous conditions. The anode was supplied with air of 80% relative humidity (RH) and the cathode with argon. Secondly, we replaced the Pt/C cathode with a photocathode consisting of 2D photocatalytic g-C₃N₄, which was placed in tandem with the photoanode (tandem-SSPEC). The tandem configuration showed a three-fold enhancement in the obtained photovoltage and a steady-state photocurrent density. The mechanism of operation is discussed in view of recent advances in surface proton conduction in absorbed water layers. The presented SSPEC cell is based on earth-abundant materials and provides a way towards systems of artificial photosynthesis, especially for areas where water sources are scarce and electrical grid infrastructure is limited or nonexistent. The only requirements to make hydrogen are humidity and sunlight.