Copper-based materials play a vital role in the electrochemical transformation of CO 2 into C 2 /C 2+ compounds. In this study, cross-sectional octahedral Cu 2 O microcrystals were prepared in situ on carbon paper electrodes via electrochemical deposition. The morphology and integrity of the exposed crystal surface (111) were meticulously controlled by adjusting the deposition potential, time, and temperature. These cross-sectional octahedral Cu 2 O microcrystals exhibited high electrocatalytic activity for ethylene (C 2 H 4 ) production through CO 2 reduction. In a 0.1 M KHCO 3 electrolyte, the Faradaic efficiency for C 2 H 4 reached 42.0% at a potential of −1.376 V vs. RHE. During continuous electrolysis over 10 h, the FE (C 2 H 4 ) remained stable around 40%. During electrolysis, the fully exposed (111) crystal faces of Cu 2 O microcrystals are reduced to Cu 0 , which enhances C-C coupling and could serve as the main active sites for catalyzing the conversion of CO 2 to C 2 H 4 .
Finned tubular air gap membrane distillation is a new membrane distillation method, and its functional performance, characterization parameters, finned tube structures, and other studies have clear academic and practical application value. Therefore, the tubular air gap membrane distillation experiment modules composed of PTFE membrane and finned tubes were constructed in this work, and three representative air gap structures, including tapered finned tube, flat finned tube, and expanded finned tube, were designed. Membrane distillation experiments were carried out in the form of water cooling and air cooling, and the influences of air gap structures, temperature, concentration, and flow rate on the transmembrane flux were analyzed. The good water-treatment ability of the finned tubular air gap membrane distillation model and the applicability of air cooling for the finned tubular air gap membrane distillation structure were verified. The membrane distillation test results show that with the tapered finned tubular air gap structure, the finned tubular air gap membrane distillation has the best performance. The maximum transmembrane flux of the finned tubular air gap membrane distillation could reach 16.3 kg/m2/h. Strengthening the convection heat transfer between air and fin tube could increase the transmembrane flux and improve the efficiency coefficient. The efficiency coefficient (σ) could reach 0.19 under the condition of air cooling. Compared with the conventional air gap membrane distillation configuration, air cooling configuration for air gap membrane distillation is an effective way to simplify the system design and offers a potential way for the practical applications of membrane distillation on an industrial scale.
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The shallow unconsolidated stratum in the offshore oilfield is characterized by large porosity, low temperature, and weak formation and often faces problems such as low density and poor compressive strength of a cement slurry, among others, which pose serious challenges to construction. A high-performance low-density cement slurry system must be used for cementing to ensure the safety of subsequent drilling and mining on-site and to reduce the cost of cement slurry for the efficient development of oil and gas fields. Based on these problems, according to the principle of particle gradation, a mixture with a high accumulation rate and low density composed of five types of mineral materials, i.e., artificial microbeads, floating beads, microsilicon, fly ash, and slag, has been developed through a large number of indoor experiments, and a set of low-cost and low-density cement slurry systems has been developed; these systems are suitable for the shallow loose formations of offshore oil fields. The cement slurry system meets the requirements of the cementing operation conducted under different temperatures and pressures. The density range is 1.4–1.7 g/cm 3 , which can be adjusted. The cement slurry is stable and exhibits good fluidity. The thickening time meets the requirements of cementing construction. Moreover, the compressive strength of the cement paste is high, and the compressive strength of cement paste is greater than 12 MPa for 24 h and 14 MPa for 48 h of curing at 50°C, which maximizes the economic benefits. The research results provide technical support for the safe and efficient development of offshore oil and gas fields.
Hydrothermal liquefaction (HTL) of microalgae produces water-soluble biocrude (WSB) and water-insoluble biocrude (WISB) simultaneously. The effects of heterogeneous catalysts (i.e. Pt/C, Ru/C, Pt/C+Ru/C) on the properties of the two types of biocrudes from Chlorella HTL were explored herein for the first time. The results show that Pt/C was favorable for the production of WISB, and reduced the WSB fraction in WSB+WISB, and obtained the highest C, H contents and the lowest N, O contents in WSB, and led to the highest yield (37.09 wt.%) and energy recovery (71.04%) of total biocrude (WSB+WISB). The WISB produced with Pt/C mainly consisted of amides (48.19%), hydrocarbons (17.68%), organic acids (12.78%), and phenols (7.74%). Pt/C prompted the cracking of high-molecular-weight compounds and the formation of low-boiling-point compounds.
How to accurately detect and efficiently sweep Cr(VI) from contaminated water has come into focus. Zirconium-based metal-organic frameworks (MOFs) play vital roles in water environmental chemistry due to excellent hydrolysis-resistant stability. However, as photochemical probes and photocatalysts, poor performances in detection sensitivity, selectivity, and photosensitiveness limit sole Zr-MOFs' applications. So, it is urgent to quest valid strategies to break through the dilemmas. Embedding luminous dyes into MOFs has been considered one of the most feasible avenues. Herein, a dual-emissive RhB@Zr-MOF with orange-yellow fluorescence has been assembled by in situ-encapsulating rhodamine B (RhB) into a zirconium-biquinoline-based MOF. Actually, within RhB@Zr-MOF, the aggregation fluorescence quenching (ACQ) effect of RhB molecules was effectively avoided. Notably, RhB@Zr-MOF exhibits a rapid fluorescence quenching response toward Cr(VI) ions with high selectivity, sensitivity, and anti-interference abilities. More interestingly, unlike the most widely reported fluorescence resonance energy transfer (FRET) between MOFs and encapsulated guest modules, photoinduced electron transfer from RhB to Zr-MOF has been confirmed by modeling the ground state and excited states of RhB@Zr-MOF using density functional theory (DFT) and time-dependent DFT (TD-DFT). The effective electron transfer makes RhB@Zr-MOF more sensitive in probing Cr2O72- and CrO42- ions with ultralow detection limit (DL) values of 6.27 and 5.26 ppb, respectively. Prominently, the detection sensitivity based on DL values has been increased about 6 and 9 times, respectively, compared with pristine Zr-MOF. Moreover, rather negative CB and positive VB potentials make RhB@Zr-MOF have excellent photochemical scavenging ability toward Cr(VI) and MO.
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