Engineered photosynthetic bacterium Rhodopseudomonas palustris is excellent at one-step CO2 biomethanation and can use near-infrared light sources, overcoming the limitations of conventional photosynthetic systems. The current study constructed a biohybrid system that deposited CdS nanoparticles on R. palustris. This biohybrid system broadens the capture of sustainable solar energy, achieving a 155 nmol·mL–1 biological CH4 production under full visible light irradiation, 13.4-fold of that by the pure R. palustris. The transcriptome profiles revealed that gene expression related to photosynthetic electron transfer chain, nitrogenase, nanofilaments, and redox stress defense was activated. Accordingly, we attributed the much-enhanced CO2 biomethanation in the biohybrid system to the remarkable increase in the intracellular reducing power and the stronger rigidity of the cells assisted by photoexcited electrons from CdS nanoparticles. Our discovery offers insight and a promising strategy for improving the current CO2–CH4 biomanufacturing system.
Hydrogenolysis has been explored as a promising approach for plastic chemical recycling. Noble metals, such as Ru and Pt, are considered effective catalysts for plastic hydrogenolysis, however, they result in a high yield of low-value gaseous products. In this research, an efficient bimetallic catalyst was developed by separate impregnation of Ni and Ru on SiO2 support resulting in liquid products yield of up to 83.1 C % under mild reaction conditions, compared to the 65.5 C % yield for the sole noble metal catalyst. The carbon distribution of the liquid products from low density polyethylene hydrogenolysis with Ni-modified catalyst also shifted to a heavier fraction, compared to that with Ru catalyst. Meanwhile, the NiRu catalyst exhibited excellent performance in suppressing the cleavage of the end-chain C–C bond, leading to a methane yield of only 10.4 C %, which was 69% lower than that of the Ru/SiO2 catalyst. Temperature programmed reduction and desorption of hydrogen and propane were further conducted to reveal the detailed mechanism of low density polyethylene hydrogenolysis over the bimetallic catalyst. The results suggested that the Ni-Ru alloy exhibited stronger H adsorption properties indicating improved hydrogen coverage on the catalyst surface thus enhancing the desorption of reaction intermediates. The carbon number distribution was ultimately skewed toward heavier liquid products.
The traditional separation of bicyclic and tricyclic aromatics from coal tar involves complicated multi-steps and consumes significantly more energy. Previous work accomplished the separation between anthracene-phenanthrene isomers using electrostatic interaction, but for the separation between bicyclic and tricyclic aromatics, electrostatic interactions are difficult to produce a recognizable effect. Naphthalene-based solvents, named as naphthaleneacetamide, naphthaleneethanol, naphthalenemethanol, naphthol, naphthylacetic acid, naphthylacetonitrile, and naphthylamine, respectively, were used for the efficient separation of naphthalene and phenanthrene via dispersion interaction. Results showed that the pre-studied structural parameters are the key factors in selecting an efficient solvent. And the substituents on the intermolecular interactions involved in the separation processes had an important impact, which were evaluated. Naphthalenemethanol exhibited a superior performance with a purity of 96.3 wt % naphthalene products because its electron-donating substituent enables the selective recognition of naphthalene via the dispersion interaction. The used naphthalene-based solvents can be regenerated and recycled via back extraction with a purity of over 90 wt % naphthalene products, suggesting solvent structural stability during the regeneration processes. Notably, the naphthalene-based solvents also demonstrated better separation performance for polycyclic aromatics from coal tar with a purity of over 80 wt % for bicyclic aromatics. This study would enhance the utilization of coal tar as a valuable source of polycyclic aromatics besides broadening the knowledge for applying non-bonded interaction in the separation of polycyclic aromatics technologies.
Ammonia is a vital component in the fertilizer and chemical industries, as well as serving as a significant carrier of renewable hydrogen energy. Compared with the industry’s principal technique, the Haber-Bosch method, for ammonia synthesis, electro/photocatalytic ammonia synthesis is increasingly recognized as a viable and eco-friendly alternative. This method enables distributed small-scale deployment and can be powered by sustainable renewable energy sources. However, the efficiency of electro/photocatalytic nitrogen reduction reaction is hindered by the challenges in activating the N≡N bond and nitrogen’s low solubility, thereby limiting its large-scale industrial applications. In this review, recent advancements in electro/photocatalytic nitrogen reduction are summarized, encompassing the complex reaction mechanisms, as well as the effective strategies for developing electro/photocatalytic catalysts and advanced reaction systems. Furthermore, the energy efficiency and economic analysis of electro/photocatalytic nitrogen fixation are deeply discussed. Finally, some unsolved challenges and potential opportunities are discussed for the future development of electro/photocatalytic ammonia synthesis.
Triboelectric nanogenerators (TENGs) are among the most promising available energy harvesting methods. Cellulose-based TENGs are flexible, renewable, and degradable. However, the flammability of cellulose prevents it from being used in open-flame environments. In this study, the lattice of cellulose was adjusted by the hydroxyl ionization of cellulose molecules, and Na+ was introduced to enhance the flame retardancy of cellulose nanofibers (CNFs). The experimental results showed that the amount of hydrogen bonding between cellulose molecules increased with the introduction of Na+ and that the limiting oxygen index reached 36.4%. The lattice spacing of cellulose increased from 0.276 to 0.286 nm, and the change in lattice structure exposed more hydroxyl groups, which changed the polarity of cellulose. The surface potential of the fibers increased from 239 to 323 mV, the maximum open-circuit voltage was 25 V·cm–2, the short-circuit current was 2.10 μA, and the output power density was 4.56 μW·cm–2. Compared with those of CNFs, the output voltage, current, and transferred charge increased by 96.8%, 517%, and 23%, respectively, and showed good stability and reliability during cyclic exposure. This study provides a valuable strategy for improving the performance of cellulose-based TENGs.
Unspecific peroxygenases exhibit high activity for the selective oxyfunctionalization of inert C(sp3)–H bonds using only H2O2 as a clean oxidant, while also exhibiting sensitivity to H2O2 concentration. CdS-based semiconductors are promising for the photosynthesis of H2O2 owing to their adequately negative potential for oxygen reduction reaction via a proton-coupled electron transfer process, however, they suffer from fast H2O2 decomposition on the surface of pristine CdS. Therefore, [Cp*Rh(bpy)H2O]2+, a highly selective proton-coupled electron transfer catalyst, was anchored onto a supramolecular polymer-grafted CdS nanoflower to construct an efficient integrated photocatalyst for generating H2O2, mitigating the surface issue of pristine CdS, increasing light absorption, accelerating photonic carrier separation, and enhancing oxygen reduction reaction selectivity to H2O2. This photocatalyst promoted the light driven H2O2 generation rate up to 1345 μmol·L–1·g–1·h–1, which was 2.4 times that of pristine CdS. The constructed heterojunction photocatalyst could supply H2O2 in situ for nonspecific peroxygenases to catalyze the C–H oxyfunctionalization of ethylbenzene, achieving a yield of 81% and an ee value of 99% under optimum conditions. A wide range of substrates were converted to the corresponding chiral alcohols using this photo-enzyme catalytic system, achieving the corresponding chiral alcohols in good yield (51%–88%) and excellent enantioselectivity (90%–99% ee).
Eucalyptus species are extensively cultivated trees commonly used for timber production, firewood, paper manufacturing, and essential nutrient extraction, while lacking consumption of the leaves increases soil acidity. The objective of this study was to recover bio-oil through microwave pyrolysis of eucalyptus camaldulensis leaves. The effects of microwave power (450, 550, 650, 750, and 850 W), pyrolysis temperature (500, 550, 600, 650, and 700 °C), and silicon carbide amount (10, 25, 40, 55, and 70 g) on the products yields and bio-oil constituents were investigated. The yields of bio-oil, gas, and residue varied within the ranges of 19.8–39.25, 33.75–46.7, and 26.0–33.5 wt %, respectively. The optimal bio-oil yield of 39.25 wt % was achieved at 650 W, 600 °C, and 40 g. The oxygenated derivatives, aromatic compounds, aliphatic hydrocarbons, and phenols constituted 40.24–74.25, 3.25–23.19, 0.3–9.77, and 1.58–7.75 area % of the bio-oils, respectively. Acetic acid (8.17–38.18 area %) was identified as a major bio-oil constituent, and hydrocarbons with carbon numbers C1 and C2 were found to be abundant. The experimental results demonstrate the potential of microwave pyrolysis as an eco-friendly and efficient way for converting eucalyptus waste into valuable bio-oil, contributing to the sustainable utilization of biomass resources.
Lower olefins, produced from syngas through Fischer-Tropsch synthesis, has been gaining worldwide attention as a non-petroleum route. However, the process demonstrates limited selectivity for target products. Herein, a hybrid catalyst system utilizing Fe-based catalyst and SAPO-34 was shown to enhance the selectivity toward lower olefins. A comprehensive study was conducted to examine the impact of various operating conditions on catalytic performance, such as space velocity, pressure, and temperature, as well as catalyst combinations, including loading pattern, and mass ratio of metal and zeolite. The findings indicated that the addition of SAPO-34 was beneficial for enhancing catalytic activity. Furthermore, compared with AlPO-34 zeolite, the strong-acid site on SAPO-34 was identified to crack the long-chain hydrocarbons, thus contributing to the lower olefin formation. Nevertheless, an excess of strong-acid sites was found to detrimentally impact the selectivity of lower olefins, attributed to the increased aromatization and polymerization of lower olefins. The detailed analysis of a hybrid catalyst in Fischer-Tropsch synthesis provides a practical strategy for improving lower olefins selectivity, and has broader implications for the application of hybrid catalyst in diverse catalytic systems.
An onboard facility shows promise in efficiently converting floating plastics into valuable products, such as methanol, negating the need for regional transport and land-based treatment. Gasification presents an effective means of processing plastics, requiring their transformation into gasification-compatible feedstock, such as hydrochar. This study explores hydrochar composition modeling, utilizing advanced algorithms and rigorous analyses to unravel the intricacies of elemental composition ratios, identify influential factors, and optimize hydrochar production processes. The investigation begins with decision tree modeling, which successfully captures relationships but encounters overfitting challenges. Nevertheless, the decision tree vote analysis, particularly for the H/C ratio, yielding an impressive R2 of 0.9376. Moreover, the research delves into the economic feasibility of the marine plastics-to-methanol process. Varying payback periods, driven by fluctuating methanol prices observed over a decade (ranging from 3.3 to 7 yr for hydrochar production plants), are revealed. Onboard factories emerge as resilient solutions, capitalizing on marine natural gas resources while striving for near-net-zero emissions. This comprehensive study advances our understanding of hydrochar composition and offers insights into the economic potential of environmentally sustainable marine plastics-to-methanol processes.
Broadening spectral response range to realize the full spectrum photocatalysis is crucial to develop photocatalysts with satisfactory light-energy conversion ability. A full-spectrum driven p-n heterojunction photocatalytic system was rationally designed through introducing the Er3+/Yb3+ co-doped BiOBr with up-conversion effect as the collector of near infrared light and photocatalysts substrate. Meanwhile, Cu3Mo2O9 with the photothermal effect as a heat source to accelerate the reaction at the surface through absorbing the near infrared light. The photocatalytic activity of BiOBr:Yb3+,Er3+/Cu3Mo2O9 composite was markedly strengthened under visible and near infrared light irradiation, and the BiOBr:Yb3+,Er3+/Cu3Mo2O9-5 composite displayed the optimal photodegradation activities for 0.03372 min–1 and 0.058 h–1, being 2.3-folds and 2.4-folds than that of pure BiOBr:Yb3+,Er3+ under the visible and near infrared light, respectively. The position of doped ions (Yb3+ and Er3+) in BiOBr:Yb3+,Er3+ was determined from the X-ray absorption fine structure spectra. And the reasonable mechanism of p-n heterojunction was proposed base on the results of experimental and density functional theory calculation. This work provides a rational strategy for the design and development of full-spectrum heterojunction photocatalysts with the up-conversion and photothermal effects to increase the photocatalytic performance.
In this study, the combustion characteristics and kinetics of cotton straw (CS) particles mixed with polyethylene (PE) film and coal gangue (CG) were investigated. The co-combustion characteristics of CS mixed with PE and CG at different heating rates were revealed by the thermogravimetric method and differential thermogravimetric method. The ignition temperature, burnout temperature, and maximum weight loss rate were measured, and the comprehensive combustion and flammability indexes were calculated. The results showed that the composite combustion characteristic index and flammability index increased with the increase in heating rate. The addition of PE and CG additives could effectively extend the combustion time. The Coats-Redfern (C-R) reaction model and N-order reaction model were used to evaluate the kinetic parameters of the blends. The results showed that 12.5% PE + 12.5% CG particles had the lowest activation energy (Ea = 103.73 kJ·mol–1) at the volatile combustion stage. The dynamics conform to the third-order dynamics model. In addition, the applicability of C-R model, Flynn-Wall-Ozawa (FWO) model, and Starink model in the calculation of activation energy was explored, and it was found that the FWO model is not suitable for the calculation of activation energy of biomass pellet combustion kinetics. This study provides a new method for the development and utilization of mixed fuel particles of cotton stalk and solid waste and expands the application prospect of biomass.
There are many disadvantages such as small detection range and environmental restrictions on application conditions, when the single quantum dot powder or solution is used for fluorescent probe detection. In this paper, the blue fluorescent silicon quantum dots and green fluorescent carbon quantum dots were prepared, and their fluorescence color changes after mixing in different proportions were investigated under different pH conditions. When the two quantum dots were mixed with a concentration of 0.1 mg·mL–1 and a mass ratio of 1:1, the fluorescence color change could be better displayed at a pH from 1 to 14. Meanwhile, the double quantum dots were prepared into two forms (ink and film), successfully realizing the device application of the fluorescent probe. The films and inkjet-printed labels were used to test the spoilage of food (pork, milk, etc.), and the color change data of the labels were collected during the spoilage test. These data were used for neural network training to predict the spoilage changes of foods.
