ZnO@C Coated Cellulose-Based Separators Control Lithium Deposition Direction to Stable Lithium Metal Batteries.

Li metal anodes have attracted attention due to their high specific capacity and low electrochemical potential. Nevertheless, the uncontrolled growth of Li dendrites hinders the practical application of Li metal batteries. Although the various approaches have made performance improvements, safety hazards still exist since Li dendrites are still growing along the anode to the separator during the continuous plating/stripping process. Herein, a straightforward method is proposed to achieve stable Li metal batteries with directional growth control by using a functional ZnO@C/cellulose membrane as a separator. The abundant pore structure and functional groups of biomass cellulose enhance the Li-ion transport and interface compatibility. The ZnO transforms in situ to form a Li-Zn alloy layer which is uniformly coated to the separator to direct uniform ion concentration polarization and charge distribution polarization, control the growth direction of Li, significantly improve the cycling stability, and promote the reversibility of the Li plating/exfoliation process. As a result, the symmetric cell exhibits an extreme lifetime of more than 4500 h and low polarization at 3 mA cm-2 . The cycling performance of the Li||LiFePO4 full cell reaches a capacity retention of 98% after 270 cycles at a mass loading of 10 mg cm-2 .

Formation behavior of PCDD/Fs during waste pyrolysis and incineration: Effect of temperature, calcium oxide addition, and redox atmosphere.

The clean and efficient utilization of municipal solid waste (MSW) has attracted increasing concerns in recent years. Pyrolysis of MSW is one of the promising options due to the production of high-value intermediates and the inhibition of pollutants at reducing atmosphere. Herein, the formation behavior of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) during MSW pyrolysis and incineration was experimentally investigated and compared. The influence of reaction temperature, CaO addition, and redox atmosphere on PCDD/Fs formation were compared and discussed. The results showed as the pyrolysis temperature increased, the mass concentration and international toxicity equivalence quantity of PCDD/Fs initially peaked at ∼750 °C before declining. Most of the generated PCDD/Fs were concentrated in the liquid and gaseous products, accounting for ∼90% of the total. Among liquid products, octachlorodibenzo-p-dioxin (O8CDD), 2,3,4,7,8-pentachlorodibenzofuran and 1,2,3,4,6,7,8-heptachlorodibenzofuran (H7CDF) were the most crucial mass concentration contributors, while in gas products, high-chlorinated PCDD/Fs, such as O8CDD, octachlorodibenzofuran (O8CDF) and 1,2,3,4,6,7,8-H7CDF were predominant. Compared to incineration, the formation of PCDD/Fs was 7-20 times greater than that from pyrolysis. This discrepancy can be attributed to the hydrogen-rich and oxygen-deficient atmosphere during pyrolysis, which effectively inhibited the Deacon reaction and the formation of C-Cl bonds, thereby reducing the active chlorine in the system. The addition of in-situ CaO additives also decreased the active chlorine content in the system, bolstering the inhibiting of PCDD/Fs formation during MSW pyrolysis.

Mechanism study of toluene removal using iron/nickel bimetallic catalysts supported on biochar.

The present study utilized rice husk biomass as a carrier to synthesize rice husk biochar loaded with iron and nickel. Mono-metallic and bimetallic catalysts were prepared for the removal of toluene as the tar model. The efficiency of the catalysts for the removal of toluene was investigated, and finally, the removal mechanisms of mono-metallic and bimetallic catalysts for toluene were revealed. The experimental results showed that the bimetallic-loaded biochar catalysts had excellent toluene removal performance, which was closely related to the ratio of loaded Fe and Ni. Among them, the catalyst DBC-Fe2.5 %-Ni2.5 % (2.5 wt% iron loading and 2.5 wt% nickel loading) obtained through secondary calcination at 700 °C achieved the highest toluene removal efficiency of 92.76 %. The elements of Fe and Ni in the catalyst were uniformly dispersed on the surface and in the pores of the biochar, and the catalyst had a layered structure with good adsorption. Under the interaction of Fe and Ni, the agglomeration and sintering of Ni were reduced, and the surface acidity of the catalyst was increased, the surface acidity was favorable for toluene removal. The iron­nickel catalyst did not form significant alloys when calcined at 400 °C, whereas strong metal interactions occurred at 700 °C, resulting in the formation of Fe0.64Ni0.36 alloy and NiFe2O4 alloy. This NiFe alloy had abundant active sites to enhance the catalytic cracking of toluene and provide lattice oxygen for the reaction. Furthermore, the functional groups on the catalyst surface also had an impact on toluene removal. The catalyst prepared in this paper reduces the cost of tar removal, can be applied to the removal of industrial pollutant tars, reduces the pollution of the environment, and provides theoretical guidance and technical reference for the efficient removal of tar.

Effect of Hydrogen Addition on Soot Formation and Emission in Acetylene Laminar Diffusion Flame.

Hydrogen (H2) has been regarded as a highly competitive alternative fuel that does not produce CO2 and soot during combustion. There are few studies of cofiring H2 with hydrocarbons. Meanwhile, the effect of hydrogen addition on soot formation and emission is questionable. In this study, the effect of H2 addition with varying ratios (between 0 and 50% by molar fraction while the remainder is nitrogen) on soot formation in acetylene (50% by molar fraction) laminar diffusion flames was experimentally and numerically investigated. Results show that with H2 addition, the flame height increases and the temperature decreases. The total soot emission and the primary particle size both increase with H2 addition. The addition of H2 promotes soot formation. In addition, the soot oxidation is weakened due to the lower flame temperature. Chemical kinetic analysis shows that the concentrations of A1, H, and H2O increase with H2 addition, which is consistent with the experimental results. According to the HACA reaction, the increase of the molar fraction of A1 and H radicals could promote PAH growth and soot formation.

Experimental Investigation on High Capacity Stove-Powered Thermoelectric Generator Incorporated with a Novel Heat Collector.

It is vital to supply necessary electric power during natural disasters and in deprived regions. A novel heat collector is proposed to improve the capacity of the stove-powered thermoelectric generator (SPTEG). Enclosed combustion walls are constructed with four W-shape copper plates, and act as a whole to be an exceptional heat collector, which was not previously reported in TEG studies. Forty TE modules are installed and two DC-DC converters are employed to stabilize the electric power. Owing to the novel heat collector, the generated electric power reaches 0.024 W/K per unit temperature difference for an individual TE module, which is 200% higher than the previous record (0.008 W/K) when forty TE modules are incorporated. The proposed SPTEG is able to generate a net electric power of 119 W, which is considerably larger than the previous record (75.2 W). The corresponding TE efficiency reaches 3.12%, which is measured at a temperature difference of 140 °C. The startup performance, power load feature, and cooling water flow rate of the SPTEG are studied in detail. Furthermore, one-dimensional theoretical analyses are conducted to explore the SPTEG performance. The theoretical electric power agrees well with the experimental data when DC-DC converters are not involved. Applying DC-DC converters to stabilize the electric power will alter the impendence of the SPTEG, resulting in much lower electric power output than that without DC-DC converters.

Experiments on Waste Heat Thermoelectric Generation for Passenger Vehicles.

In order to utilize waste heat from passenger vehicles by a thermoelectric generator (TEG), a lab-scale TEG with a sufficient low-pressure drop was designed and tested. The waste heat from a 2.0 L petrol engine was simulated by using an air-circulation channel with an adjustable electric heater and a speed control motor. The TEG consisted of an integrated molding designed aluminum-finned heat collector, twenty thermoelectric modules, and a set of water-cooled heat sinks. Experiments were conducted in terms of power load feature, pressure drop, heat collection efficiency, thermoelectric efficiency and overall efficiency. It was found that the hot-end temperature was much lower (46.9%) than the flue gas temperature because the trade-off between fin area and pressure drop had to be considered. The obtained maximum electric power was 36.4 W, and the corresponding pressure drop was 36 Pa. The corresponding heat collection efficiency was 46.5%, and the thermoelectric efficiency was 2.88%, which agreed well with the theoretical prediction of 3.38%. As a result, an overall efficiency of 1.21% was reached. The present work firstly demonstrated a waste-heat-recovering TEG prototype with a balanced overall efficiency of over 1%, and a pressure drop of less than 50 Pa. On the other hand, the maximum electric power was difficult to fully extract. The charging power to a battery with a maximum power point tracking direct current-direct current converter was experimentally verified to work at a much higher conversion efficiency (15.3% higher) than regular converters.

Hydrogen-Rich and Clean Fuel Gas Production from Co-pyrolysis of Biomass and Plastic Blends with CaO Additive.

The treatment and disposal of waste biomass and plastics are of great importance to achieve both waste management and resource recycling. In this work, pyrolysis of biomass and plastic blends were investigated to identify the influence of temperature and in situ CaO addition on the production of hydrogen-rich, HCl-free, and low tar content fuel gases. The results show that the increase in temperature and the use of CaO significantly improved both the quantity and quality of the fuel gas and mitigated the formation of tar compounds and HCl. Moreover, H2 yield was significantly improved from 0.30 to 3.68 mmol/g with the increase in temperature from 550 to 850 °C. Also, the use of in situ CaO significantly increased the H2 yield by 28-88%. The H2/CO ratio was also enhanced from 0.35 to 1.50 with the temperature increase and CaO addition. Tar removal efficiency reached approximately 70.09% with the use of CaO at 850 °C. The produced HCl gas could be effectively absorbed by CaO through dechlorination reactions to form CaClOH at a highest mitigation efficiency of 92.37%. The results could be used to develop clean and efficient treatment technologies of waste biomass and plastics.

Nano-silica extracted from rice husk and its application in acetic acid steam reforming.

Nano-silica extracted from rice husk and its application in acetic acid steam reforming was studied in the paper. A simple and efficient heat treatment method was used to extract high specific surface area silica from rice husk. It was found that the acid leaching process was beneficial for the removal of metal impurities and the decomposition of organic substances. The carbon residue decreased and sample purity increased with increasing temperature. At 600 °C, silica with the yield of 21.7% and the purity of 99.45% was obtained. The specific surface area was as high as 335 m2 g-1, and the corresponding average pore diameter was 4.95 nm. Nano-silica extracted from rice husk was applied as a support in the preparation of an acetic acid steam reforming catalyst (Ni/RH-SiO2). Ni/RH-SiO2 showed a better performance than Ni/SiO2, which may be due to the higher interaction between Ni and SiO2 in Ni/RH-SiO2. When the reforming temperature was 700 °C, carbon conversion of 95.3% and H2 yield of 2.38 mol mol-1 were obtained. Carbon deposition was found after a 6 h test, mainly in the form of filamentous carbon. The carbon deposition amount of spent-Ni/RH-SiO2 was lower than that of spent-Ni/SiO2.

Numerical modeling of ultrasonic cavitation by dividing coated microbubbles into groups.

Homogeneous cavitation models usually use an average radius to predict the dynamics of all bubbles. However, bubbles with different sizes may have quite different dynamic characteristics. In this study, the bubbles are divided into several groups by size, and the volume-weighted average radius is used to separately calculate the dynamics of each group using a modified bubble dynamics equation. In the validation part, the oscillations of bubbles with two sizes are simulated by dividing them into 2 groups. Comparing with the predictions by the Volume of Fluid (VOF) method, the bubble dynamics of each size are precisely predicted by the proposed model. Then coated microbubbles with numerous sizes are divided into several groups in equal quantity, and the influence of the group number is analyzed. For bubble oscillations at f = 0.1 MHz and 1 MHz without ruptures, the oscillation amplitude is obviously under-estimated by the 1-group model, while they are close to each other after the group number increases to 9. For bubble ruptures triggered by Gaussian pulses, the predictions are close to each other when more than 5 groups are used.

Testing and Optimizing a Stove-Powered Thermoelectric Generator with Fan Cooling.

In order to provide heat and electricity under emergency conditions in off-grid areas, a stove-powered thermoelectric generator (STEG) was designed and optimized. No battery was incorporated, ensuring it would work anytime, anywhere, as long as combustible materials were provided. The startup performance, power load feature and thermoelectric (TE) efficiency were investigated in detail. Furthermore, the heat-conducting plate thickness, cooling fan selection, heat sink dimension and TE module configuration were optimized. The heat flow method was employed to determine the TE efficiency, which was compared to the predicted data. Results showed that the STEG can supply clean-and-warm air (625 W) and electricity (8.25 W at 5 V) continuously at a temperature difference of 148 °C, and the corresponding TE efficiency was measured to be 2.31%. Optimization showed that the choice of heat-conducting plate thickness, heat sink dimensions and cooling fan were inter-dependent, and the TE module configuration affected both the startup process and the power output.