High-Performance MoS2/SWCNT Composite Films for a Flexible Thermoelectric Power Generator.

Single-walled carbon nanotube (SWCNT)-based thermoelectric materials have been extensively studied in the field of flexible wearable devices due to their high flexibility and excellent electrical conductivity (σ). However, poor Seebeck coefficient (S) and high thermal conductivity limit their thermoelectric application. In this work, free-standing MoS2/SWCNT composite films with improved thermoelectric performance were fabricated by doping SWCNTs with MoS2 nanosheets. The results demonstrated that the energy filtering effect at the MoS2/SWCNT interface increased the S of composites. In addition, the σ of composites was also improved due to the reason that S-π interaction between MoS2 and SWCNTs made good contact between MoS2 and SWCNTs and improved carrier transport. Finally, the obtained MoS2/SWCNT showed a maximum power factor of 131.9 ± 4.5 µW m-1 K-2 at room temperature with a σ of 680 ± 6.7 S cm-1 and an S of 44.0 ± 1.7 µV K-1 at a MoS2/SWCNT mass ratio of 15:100. As a demonstration, a thermoelectric device composed of three pairs of p-n junctions was prepared, which exhibited a maximum output power of 0.43 µW at a temperature gradient of 50 K. Therefore, this work offers a simple method of enhancing the thermoelectric properties of SWCNT-based materials.

Enhancement Effect of the C60 Derivative on the Thermoelectric Properties of n-Type Single-Walled Carbon Nanotube-Based Films.

Obtaining air-stable and high-performance flexible n-type single-walled carbon nanotube (SWCNT)-based thermoelectric films used in wearable electronic devices is a challenge. In this work, the microstructure and thermoelectric properties of n-type SWCNT-based films have been optimized via doping C60 and its derivative into polyethylenimine/single-walled carbon nanotube (PEI/SWCNT) films. The result demonstrated that the dispersity of triethylene glycol-modified C60 (TEG-C60) was better in PEI/SWCNT films than that of pure C60. Among the prepared composite films, TEG-C60-doped PEI/SWCNT (TEG-C60/PEI/SWCNT) films exhibited the highest TE performance, achieving a peak electrical conductivity of 923 S cm-1 with a Seebeck coefficient of -42 µV K-1 at a TEG-C60/SWCNT mass ratio of 1:100. Compared to that of PEI/SWCNT, the power factor was increased significantly from 40 to 162 µW m-1 K-2 after the addition of TEG-C60, which was higher than that of films after the addition of C60. In addition, the n-type doped SWCNT films had good air stability at high temperatures, and the Seebeck coefficients of C60/PEI/SWCNT and TEG-C60/PEI/SWCNT at 120 °C were still negative and remained at 92% and 85%, respectively, after 20 days. Furthermore, a flexible TE device consisting of five pairs of p-n junctions was assembled using the optimum hybrid film, which generated a maximum output power of 3.6 µW at a temperature gradient of 50.2 K. Therefore, this study provides a facile way to enhance the thermoelectric properties of n-type carbon nanotube-based materials, which have potential application in flexible power generators.

Aerosol Emissions of Amine-Based CO2 Absorption System: Effects of Condensation Nuclei and Operating Conditions.

Amine emissions from a post-combustion CO2 capture process can lead to solvent loss and serious environmental issues. The emission characteristics of amine mixtures and influencing factors are seldom reported. This work comprehensively investigated emissions of AMP (2-amino-2-methyl-1-propanol)/MEA (monoethanolamine) from a 3.6 Nm3/h flue gas CO2 capture platform. The condensation nuclei in flue gas dominated the generation of amine aerosols and resulted in a heavy total amine loss of over 1400 mg/Nm3, which is equivalent to 5.88 kg/t CO2 captured under the high nuclei concentration scenario. Inside the absorber, a higher CO2 concentration and lower lean solvent CO2 loading can significantly promote the growth of aerosols due to the intensive reaction of CO2 absorption. The maximum amine emissions were observed at 8-12 vol % CO2. The flue gas temperature and liquid/gas ratio had insignificant effects on aerosol emissions, while amine emissions after the absorber increased 340-500% as the lean solvent temperature increased from 30 to 50 °C. A synergistic control strategy of nuclei pretreatment, operating optimization, and water scrubbing can effectively reduce amine emissions to 4.0 mg/Nm3 MEA and 8.3 mg/Nm3 AMP.

Pyrolysis of a typical low-rank coal: application and modification of the chemical percolation devolatilization model.

The chemical percolation devolatilization (CPD) model can simulate the formation of various products during the coal pyrolysis process and predict the products composition relatively accurately. In this study, the pyrolysis products of a typical low-rank coal were calculated using the CPD model, and several model improvements were proposed by combining the experimental results in a lab-scale pyrolysis system. The chemical structural parameters calculated from the Genetti correlations were verified by adjusting the initial fraction of char bridges (c 0) from 0.098 to 0.25. A yield difference (Δf tar) was defined in this paper to analyze the consumption of tar fragments in the model, and it was found that the deviations between experiments and calculations resulted from the weak influence of crosslinking. A modification expression was adopted to amplify the tar consumption: , which improved the accuracy of the model on the tar yield with errors of less than ±0.5 wt%. Furthermore, this paper also developed a correlation in an exponential form about gas composition, which attempted to extend the application of the CPD coalification reference mesh for the coal away from interpolation triangles. The improved model by the correlation predicted CH4, CO, and CO2 yields for this typical low-rank coal accurately in most cases. Compared with the original CPD model, the modified model showed better agreement with the experimental results and predicted 71.4% and 88.6% of the data points in this work within ±10% and ±20% errors, respectively.

[Experimental study on CO2 absorption by aqueous ammonia-based blended absorbent].

A crucial problem for the promising absorbent aqueous ammonia (NH3) is the low CO2 absorption rate. The mass transfer coefficient (K(G)) of CO2 in aqueous NH3-based absorbents on a wetted wall column facility was investigated. Monoethanolamine (MEA), piperazine (PZ), 1-methyl piperazine (1-MPZ) and 2-methyl piperazine (2-MPZ) were introduced into NH3 solutions as additives, all of which significantly increased the mass transfer coefficient of CO2 in the solutions. With CO2 loading of 0, 0.1, 0.3, 0.5 mol x mol(-1), K(G) of 3 mol x L(-1) NH3 + 0.3 mol x L(-1) PZ blended solution increased by 2, 2.2, 2.2, and 1.9 fold as compared to that of 3 mol x L(-1) NH3. Typically, PZ, the additive with best performance, was chosen for further study. The effects of temperature and PZ concentration on CO2 absorption in PZ solution and the blended NH3/PZ solution. The calculated pseudo first order rate constant [42.7 m3 x (mol x s)(-1)] was analyzed to further elucidate the reaction mechanism in the blended NH3/PZ solution.