Efficient conversion of nitrogen oxides (NOx) in oxygen-rich exhaust remains a major challenge for selective catalytic reduction (SCR) with C3H6 and CO, especially at low temperature (<200 degrees C). In this study, in-situ coprecipitation method was used to support Cu-Mn-Ce on layered double oxide (LDO), which was then anchored on reduced graphene oxide (rGO) and further doped with Co, Ni, or Al, to prepare the nanocomposite catalysts, Cu-Mn-Ce-LDO/rGO/M. The C3H6/CO-SCR reactivity of the catalysts was evaluated by a fixed bed microreactor. Results proved that the nanocomposite catalysts have two functions: capture and storage NO via strong adsorption on oxygen-vacancy-rich coordinatively unsaturated sites (CUS) at lower temperature and reduce NO to N-2 via C3H6/CO-SCR at higher temperature. The capacity for NO capture-storage was between 159.35-58.81 mu mol. g(-1). The NO conversion and N-2 selectivity was proven to be as high as 92.5 % and 93.7 % at 250 degrees C for Co-doped catalyst, i.e., CuMnCe-LDO/rGO/Co, during the C3H6/CO-SCR reaction. The catalysts showed a strong resistance to SO2, above 90 % of NO conversion and 94 % of N-2 selectivity in the presence of 1000 ppm of SO2. Detailed characterizations illustrated that finely dispersed oxide nanodomains were anchored to rGO surface with abundant defects, which enhanced NO adsorption and reduction. In-situ DRIFTS showed that bidentate nitrates were the dominant intermediates, alongside bridging and monodentate nitrates were also formed. A mechanism combined the C3H6-driven Langmuir-Hinshelwood mechanism below 200 degrees C and Mars-van-Krevelen mechanism above 250 degrees C for CO oxidation was proposed.
This study first proposed a comprehensive separation strategy combining liquid–liquid extraction and selective crystallization to achieve the selective recovery of guaiacol from the phenolic wastewater present of biomass pyrolysis oil. Through high-throughput screening of 136 DSILs using the COSMO-RS model, [BMPY]0.5[HMIM]0.5[NTF2] was determined as the optimal extractant. The experimental results showed that the extraction efficiency of this DSIL for the mixed phenolic compounds exceeded 95%, and it exhibited excellent cycle stability. Subsequently, selective crystallization between piperazine and guaiacol was employed to selectively recover guaiacol from the complex phenolic mixture. Moreover, molecular simulation revealed the important roles of hydrogen bonds and van der Waals interactions in molecular recognition during extraction and crystallization. This study systematically clarified the specific recognition mechanism between molecules from microscopic mechanisms to macroscopic experiments, providing a new approach for the efficient recovery of phenolic compounds from wastewater.
Chemical looping combustion (CLC) has achieved in situ CO2 separation during coal combustion. Oxygen carriers (OCs) as the core components provide lattice oxygen and function as catalysts in the mercury removal process. However, the complete mercury removal mechanism during the redox process of OCs has not been fully understood. Co3O4 has attracted widespread attention due to its excellent catalytic oxidation activity. Therefore, it is essential to study the interaction mechanisms between Co3O4 and elemental mercury (Hg0) during the redox process of OCs. Experimental and DFT methods reveal that mercury removal efficiency decreases with increasing reduction degree (Co3O4 > CoO > CoO0.75 > CoO0.5 > Co). The primary mechanism is the oxidation of Hg0 to HgO via lattice oxygen following the Mars-Maessen pathway, rather than adsorption. CO2 enhances Hg0 oxidation performance by replenishing lattice oxygen. When oxygen release from CoO reaches 50% (CoO0.5), the generated HgO becomes difficult to desorb from the oxygen carrier surface. When highly reduced, Co adsorbs Hg0, which is then oxidized and desorbed as HgO upon re-oxidation by O2. The complete mechanism of Hg0 oxidation and desorption over Co3O4 during the redox process is revealed. This work provides mechanistic insight into mercury control during coal CLC.
A cathode with thermal expansion compatibility, high catalytic activity toward the oxygen reduction reaction, and excellent high-temperature stability is essential for the commercialization of solid oxide fuel cells (SOFCs). In this study, two medium-entropy Swedenborgite-type oxides, Y0.25Lu0.25Ca0.25In0.25BaCo4−xZnxO7+δ (denoted as YLCIBCZ for x = 1 and YLCIBCZ1.5 for x = 1.5), were developed by applying a medium-entropy strategy at the Y-site and Zn doping at the Co-site of YBaCo4O7. Both cathodes were synthesized via solid-state reaction. Their average thermal expansion coefficients from 30 to 1000 °C were 10.1 × 10−6 K−1 (YLCIBCZ) and 11.1 × 10−6 K−1 (YLCIBCZ1.5), showing good thermal compatibility with the La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) electrolyte. With increasing Zn content, the electrical conductivities decreased from 17.4 to 7.8 S cm−1 at 800 °C. Both oxides exhibited excellent phase stability between 600 and 800 °C, good chemical compatibility with LSGM, and superior stability in CO2-containing atmospheres. Electrochemical tests showed low area-specific resistances of 0.032 (YLCIBCZ) and 0.109 Ω cm2 (YLCIBCZ1.5) at 800 °C. Single cells with these cathodes achieved maximum power densities of 1275 and 1210 mW cm−2 at 800 °C. The combination of thermal compatibility, structural stability, and excellent electrochemical performance demonstrates that YLCIBCZ and YLCIBCZ1.5 serve as promising cathode candidates for intermediate-temperature SOFCs. This work validates the medium-entropy design strategy and provides a new pathway for developing high-performance SOFC cathodes.
Wickless vapor chambers (VCs) are gaining popularity in electronics thermal management owing to their high integration and minimal thickness. To meet the demand for miniaturization and integration in electronic devices, it is necessary to optimize the internal microstructure of wickless VCs to enhance their thermal performance. This study investigates strategies to enhance the thermal performance of VCs using microstructured surfaces, including cavity structure (CS), finned structure (FS), and mixed structure (MS) with varying wettabilities. The bubble/droplet dynamics, boiling heat transfer coefficient (BHTC), critical heat flux (CHF), and thermal resistance of VCs with different microstructured surfaces are analyzed in detail. Results show that the MS surface effectively enhances the dynamic behavior of bubbles and droplets during the phase change process and significantly reduces boiling surface temperature due to its composite structural features. Based on the MS surface, a heterogeneous wettable surface is proposed to further improve the thermal performance of VC. It constructs a hydrophilic-hydrophobic distribution within the cavities and a gradient wettable surface on the conical fins. This configuration precisely regulates the pinning-slippage behavior of the three-phase contact line through Marangoni flow, which not only enhances nucleation sites activity but also accelerates the detachment of bubbles/droplets. Two optimized surfaces were obtained through coupling the microstructure shape and wettability distribution optimization, exhibiting superior performance in improving the CHF and BHTC, respectively. Under high heat flux conditions, the CHF-optimized surface reduces thermal resistance by 34.2% compared to a flat surface while sustaining high heat loads. For low heat flux scenarios, the BHTC-optimized surface achieves up to 52.6% reduction in thermal resistance.
