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Continuous CO2 emissions from the modern development of human society and industry is a significant contributor to global climate changes. CO2 capture and utilization has been considered by the society for abating CO2 emissions, which primarily involves capturing CO2 from various sources (as well as the atmosphere) and converting it to value-added chemicals/fuels (ideally using renewable energies). Nonthermal plasma (NTP) catalysis, which operates under mild conditions and is [Detail] ...
Download coverSodium-ion batteries (SIBs) have garnered significant interest in energy storage due to their similar working mechanism to lithium ion batteries and abundant reserves of sodium resource. Exploring facile synthesis of a carbon-based anode materials with capable electrochemical performance is key to promoting the practical application of SIBs. In this work, a combination of petroleum pitch and recyclable sodium chloride is selected as the carbon source and template to obtain hard carbon (HC) anode for SIBs. Carbonization times and temperatures are optimized by assessing the sodium ion storage behavior of different HC materials. The optimized HC exhibits a remarkable capacity of over 430 mAh·g–1 after undergoing full activation through 500 cycles at a density of current of 0.1 A·g–1. Furthermore, it demonstrates an initial discharge capacity of 276 mAh·g–1 at a density of current of 0.5 A·g–1. Meanwhile, the optimized HC shows a good capacity retention (170 mAh·g–1 after 750 cycles) and a remarkable rate ability (166 mAh·g–1 at 2 A·g–1). The enhanced capacity is attributed to the suitable degree of graphitization and surface area, which improve the sodium ion transport and storage.
The precise engineering of surface active sites is deemed as an efficient protocol for regulating surfaces and catalytic properties of catalysts. Defect engineering is the most feasible option to modulate the surface active sites of catalysts. Creating specific active sites on the catalyst allows precise modulation of its electronic structure and physicochemical characteristics. Here, we outlined the engineering of several types of defects, including vacancy defects, void defects, dopant-related defects, and defect-based single atomic sites. An overview of progress in fabricating structural defects on catalysts via de novo synthesis or post-synthetic modification was provided. Then, the applications of the well-designed defective catalysts in energy conversion and environmental remediation were carefully elucidated. Finally, current challenges in the precise construction of active defect sites on the catalyst and future perspectives for the development directions of precisely controlled synthesis of defective catalysts were also proposed.
Carbon dioxide fixation presents a potential solution for mitigating the greenhouse gas issue. During carbon dioxide fixation, C1 compound reduction requires a high energy supply. Thermodynamic calculations suggest that the energy source for cofactor regeneration plays a vital role in the effective enzymatic C1 reduction. Hydrogenase utilizes renewable hydrogen to achieve the regeneration and supply cofactor nicotinamide adenine dinucleotide (NADH), providing a driving force for the reduction reaction to reduce the thermodynamic barrier of the reaction cascade, and making the forward reduction pathway thermodynamically feasible. Based on the regeneration of cofactor NADH by hydrogenase, and coupled with formaldehyde dehydrogenase and formolase, a favorable thermodynamic mode of the C1 reduction pathway for reducing formate to dihydroxyacetone (DHA) was designed and constructed. This resulted in accumulation of 373.19 μmol·L–1 DHA after 2 h, and conversion reaching 7.47%. These results indicate that enzymatic utilization of hydrogen as the electron donor to regenerate NADH is of great significance to the sustainable and green development of bio-manufacturing because of its high economic efficiency, no by-products, and environment-friendly operation. Moreover, formolase efficiently and selectively fixed the intermediate formaldehyde (FALD) to DHA, thermodynamically pulled formate to efficiently reduce to DHA, and finally stored the low-grade renewable energy into chemical energy with high energy density.
Developing hierarchical and nanoscale ZSM-5 catalysts for diffusion-limited reactions has received ever-increasing attention. Here, ZSM-5 architecture integrated with hierarchical pores and nanoscale crystals was successfully prepared via in situ self-assembly of nanoparticles-coated silicalite-1. First, the oriented attachment of amorphous nanoparticles on external surface of silicalite-1 was achieved by controlling the alkalinity of Si-Al coating solution. The partial exposure of the external surface of silicalite-1 ensured the uniform removal of silicon in the bulk phase for the creation of hierarchical pores during the subsequent desilication-recrystallization. The uniform removal of silicon species in the bulk phase was mainly due to the synergistic effect of surface protection and alkaline etching, which could be balanced by regulating the relative amount of tetrapropylammonium cation and OH– in desilication-recrystallization solution. Importantly, the removed silicon from silicalite-1 recrystallized and in situ assembled into final ZSM-5 nanocrystals induced by surface Si-Al nanoparticles. The hierarchical pores and nanoscale crystals on this integrated architecture not only promoted the removal of coke precursors from micropores but also provided large external specific surface (91 m2·g–1) for coke deposition. Consequently, a much longer catalytic lifetime was achieved for methanol-to-aromatics reaction compared to conventional hollow structure ZSM-5 (84 h vs 46 h), with relatively high stability.
Electrified non-thermal plasma (NTP) catalytic hydrogenation is the promising alternative to the thermal counterparts, being able to be operated under mild conditions and compatible with green electricity/hydrogen. Rational design of the catalysts for such NTP-catalytic systems is one of the keys to improve the process efficiency. Here, we present the development of siliceous mesocellular foam (MCF) supported Cu catalysts for NTP-catalytic CO2 hydrogenation to methanol. The findings show that the pristine MCF support with high specific surface area and large mesopore of 784 m2·g−1 and ~8.5 nm could promote the plasma discharging and the diffusion of species through its framework, outperforming other control porous materials (viz., silicalite-1, SiO2, and SBA-15). Compared to the NTP system employing the bare MCF, the inclusion of Cu and Zn in MCF (i.e., Cu1Zn1/MCF) promoted the methanol formation of the NTP-catalytic system with a higher space-time yield of methanol at ~275 μmol·gcat−1·h−1 and a lower energy consumption of 26.4 kJ·
Amino acids are important nitrogen carriers in biomass and entail a broad spectrum of industrial uses, most notably as food additives, pharmaceutical ingredients, and raw materials for bio-based plastics. Attaining detailed information in regard to the fragmentation of amino acids is essential to comprehend the nitrogen transformation chemistry at conditions encountered during hydrothermal and pyrolytic degradation of biomass. The underlying aim of this review is to survey literature studies pertinent to the complex structures of amino acids, their formation yields from various categories of biomass, and their fragmentation routes at elevated temperatures and in the aqueous media. Two predominant degradation reactions ensue in the decomposition of amino acids, namely deamination and decarboxylation. Notably, minor differences in structure can greatly affect the fate for each amino acid. Moreover, amino acids, being nitrogen-rich compounds, play pivotal roles across various fields. There is a growing interest in producing varied types and configurations of amino acids. Microbial fermentation appears to a viable approach to produce amino acids at an industrial scale. One innovative method under investigation is catalytic synthesis using renewable biomass as feedstocks. Such a method taps into the inherent nitrogen in biomass sources like chitin and proteins, eliminating the need for external nitrogen sources. This environmentally friendly approach is in line with green chemistry principles and has been gathering momentum in the scientific community.
Single-atom catalysts (SACs), characterized by exceptionally high atom efficiency, have garnered significant attention across various catalytic reactions. Recent studies have showcased SACs with robust capabilities for precise catalysis, specifically targeting reactions along designated pathways. This review focuses on the advances in the precise activation and reconstruction of chemical bonds on SACs, including precise activation of C–O and C–H bonds and selective couplings involving C–C and C–N bonds. Our discussion begins with a thorough exploration of the factors that render SACs skilled in precise catalytic processes, encompassing the narrow d-band electronic state of single atom site resulting in the adsorption tendency, isolate site resulting in unique adsorption structure, and synergy effect of a single atom site with its neighbors. Subsequently, we elaborate on the applications of SACs in electrocatalysis and thermocatalysis including four prominent reactions, namely, electrochemical CO2 reduction, urea electrochemical synthesis, CO2 hydrogenation, and CH4 activation. Then the concept of rational design of SACs for precisely controlling reaction pathways is discussed from the aspects of pore structure design, support-metal strong interaction, and support hydrophilic/hydrophobic. Finally, we summarize the challenges encountered by SACs in the field of precise catalytic processes and outline prospects for their further development in this domain.
Sodium-ion batteries (SIBs), which serve as alternatives or supplements to lithium-ion batteries, have been developed rapidly in recent years. Designing advanced high-performance layered NaxTMO2 cathode materials is beneficial for accelerating the commercialization of SIBs. Herein, the recent research progress on scalable synthesis methods, challenges on the path to commercialization and practical material design strategies for layered NaxTMO2 cathode materials is summarized. Co-precipitation method and solid-phase method are commonly used to synthesize NaxTMO2 on mass production and show their own advantages and disadvantages in terms of manufacturing cost, operative difficulty, sample quality and so on. To overcome drawbacks of layered NaxTMO2 cathode materials and meet the requirements for practical application, a detailed and deep understanding of development trends of layered NaxTMO2 cathode materials is also provided, including high specific energy materials, high-entropy oxides, single crystal materials, wide operation temperature materials and high air stability materials. This work can provide useful guidance in developing practical layered NaxTMO2 cathode materials for commercial SIBs.
Microwave-assisted pyrolysis is an effective method for recycling plastic wastes into oils that can be used for aviation fuels. In this study, energy and economic analyses of aviation oil production from microwave-assisted pyrolysis of polystyrene were performed. The total energy efficiency, recovered energy efficiency, unitary cost, unitary energy economic cost, relative cost difference, and energy economic factor were detailed. And the effects of microwave power, pyrolysis temperature, microwave absorbent loading, and microwave absorbent type on these parameters were covered. It was found that pyrolysis temperature has the most significant effect on the unitary cost and unitary energy economic cost of aviation oil, and-microwave absorbent type has a significant influence on energy economic factor during the whole microwave-assisted pyrolysis process. The optimum reaction conditions at the tonnage system for pyrolysis of 1 t polystyrene were microwave power of 650 W, pyrolysis temperature of 460 °C, and silicon carbide (microwave absorbent) at a loading of 2 t (twice than feedstock loading). At these optimal conditions, the total energy efficiency, recovered energy efficiency, unitary cost, unitary energy economic cost, relative cost difference, and energy economic factor were 62.78%, 96.51%, 3.21 × 104 yuan·t–1, 779 yuan·GJ–1, 1.49, and 71.02%, respectively.
Methane cracking is considered a bridge technology between gray and green hydrogen production processes. In this work an experimental study of methane cracking in molten tin is performed. The tests were conducted in a quartz reactor (i.d. = 1.5 cm, L = 20 cm) with capillary injection, varying temperature (950–1070 °C), inlet methane flow rate (30–60 mL·min–1) and tin height (0–20 cm). The influence of the residence time in the tin and in the headspace on methane conversion and on carbon morphology was investigated. The conversions obtained in tin and in the empty reactor were measured and compared with results of detailed kinetic simulations (CRECK). Furthermore, an expression of a global kinetic constant for methane conversion in tin was also derived. The highest conversion (65% at Q0 = 30 mL·min–1 and t = 1070 °C) is obtained for homogeneous gas phase reaction due to the long residence time (70 s), the presence of tin leads to a sharp decrease of residence time (1 s), obtaining a conversion of 35% at 1070 °C, thus meaning that tin owns a role in the reaction. Carbon characterization (scanning electron microscopy, Raman) reported a change in carbon toward sheet-like structures and an increase of the carbon structural order in the presence of molten tin media.
