Green Energy & Environment最新文献

Combining the unique advantages of aqueous electrolytes and metallic Zn anode, rechargeable aqueous Zn-ion batteries (ZIBs) are of great promise for large-scale energy storage applications due to their inherent high safety, low cost, and environmental friendliness. As the essential component of ZIBs, Zn metal anode suffers from severe dendrite formation and inevitable side reactions (e.g. corrosion and hydrogen evolution) in aqueous electrolytes, which leads to low Coulombic efficiency and inferior cycling stability, impeding their large-scale applications. To be compatible with satisfactory aqueous ZIBs, Zn anode has been modified from various perspectives and focus areas. Herein, based on their intrinsic characteristics, we review the related improvement strategies for Zn anode, including interphase, substrate, and bulk design, so as to achieve an in-depth understanding of Zn anode optimization. Furthermore, the timely summary of characterization methods for Zn anodes are also performed for the first time, from both thermodynamic and kinetics perspectives, which is particularly helpful for beginners to understand the complicated characterizations and employ suitable methods. Finally, certain noteworthy points are put forward for subsequent investigation of aqueous ZIBs. It is expected that this review will enlighten researchers to explore more efficient optimization strategies for Zn anode in aqueous electrolytes.

Hydrogel electrolyte is especially suitable for solid-state Al-air batteries targeted for various portable applications, which may, however, lead to continuous Al corrosion during battery standby. To tackle this issue, an ethanol gel electrolyte is developed for Al-air battery for the first time in this work, by using KOH as solute and polyethylene oxide as gelling agent. The ethanol gel is found to effectively inhibit Al corrosion compared with the water gel counterpart, leading to stable Al storage. When assembled into an Al-air battery, the ethanol gel electrolyte achieves a much improved discharge lifetime and specific capacity, which are 5.3 and 4.1 times of the water gel electrolyte at 0.1 mA cm⁻², respectively. By studying the gel properties, it is found that a lower ethanol purity can improve the battery power output, but at the price of decreased discharge efficiency. On the contrary, a higher polymer concentration will decrease the power output, but can bring extra benefit to the discharge efficiency. As for the gel thickness, a moderate value of 1 mm is preferred to balance the power output and energy efficiency. Finally, to cater the increasing market of flexible electronics, a flexible Al-air battery is developed by impregnating the ethanol gel into a paper substrate, which can function normally even under serious deformation or damage.

Transfer hydrogenation (TH) with in situ generated hydrogen donor is of great importance in reduction reactions, and an alternative strategy to traditional hydrogenation processes involving pressurized molecular hydrogen. Ammonia borane (NH₃BH₃, AB) is a promising material of hydrogen storage, and it has attracted much attention in reductive organic transformations owing to its high activity, good atom economy, non-toxicity, sustainability, and ease of transport and storage. This review focuses on summarizing the recent progress of AB-mediated TH reactions of diverse substrates including nitro compounds, nitriles, imines, alkenes, alkynes, carbonyl compounds (ketones and aldehydes), carbon dioxide, and N- and O-heterocycles. Syntheses protocols (metal-containing and metal-free), the effect of reaction parameters, product distribution, and variation of reactivity are surveyed, and the mechanism of each reaction involving the action mode of AB as well as structure-activity relationships is discussed in detail. Finally, perspectives are presented to highlight the challenges and opportunities for AB-enabled TH reactions of unsaturated compounds.

Low-carbon hydrogen can play a significant role in decarbonizing the world. Hydrogen is currently mainly produced from fossil sources, requiring additional CO₂ capture to decarbonize, which energy intense and costly. In a recent Green Energy & Environment paper, Cheng and Di et al. proposed a novel integration process referred to as SECLR_HC to generate high-purity H₂ by in-situ separation of H₂ and CO without using any additional separation unit. Theoretically, the proposed process can essentially achieve the separation of C and H in gaseous fuel via a reconfigured reaction process, and thus attaining high-purity hydrogen of ∼99%, as well as good carbon and hydrogen utilization rates and economic feasibility. It displays an optimistic prospect that industrial decarbonization is not necessarily expensive, as long as a suitable CCS measure can be integrated into the industrial manufacturing process.

Catalytic oxidation of benzene with N₂O to phenol over the hierarchical and microporous Fe/ZSM-5-based catalysts in a continuous fixed-bed reactor was investigated. The spent catalyst was in-situ regenerated by an oxidative treatment using N₂O and in total 10 reaction-regeneration cycles were performed. A 100% N₂O conversion, 93.3% phenol selectivity, and high initial phenol formation rate of 16.49 ± 0.06 mmol_phenol g_catalyst⁻¹ h⁻¹ at time on stream (TOS) of 5 min, and a good phenol productivity of 147.06 mmol_phenol g_catalyst⁻¹ during catalyst life-time of 1800 min were obtained on a fresh hierarchical Fe/ZSM-5-Hi2.8 catalyst. With the reaction-regeneration cycle, N₂O conversion is fully recovered within TOS of 3 h, moreover, the phenol productivity was decreased ca. 2.2 ± 0.8% after each cycle, leading to a total phenol productivity of ca. 0.44 ton_phenol kg_catalyst⁻¹ estimated for 300 cycles. Catalyst characterizations imply that the coke is rapidly deposited on catalyst surface in the initial TOS of 3 h (0.28 mg_c g_catalyst⁻¹ min⁻¹) and gradually becomes graphitic during the TOS of 30 h with a slow formation rate of 0.06 mg_c g_catalyst⁻¹ min⁻¹. Among others (e.g., the decrease of textural property and acidity), the nearly complete coverage of the active Fe-O-Al sites by coke accounts for the main catalyst deactivation. Besides these reversible deactivation characteristics related to coking, the irreversible catalyst deactivation is also observed with the reaction-regeneration cycle. The latter is reflected by a further decreased amount of the active Fe-O-Al sites, which agglomerate on catalyst surface with the cycle, likely associated with the hard coke residue that is not completely removed by the regeneration.

Lithium metal batteries represent promising candidates for high-energy-density batteries, however, many challenges must still be overcome, e.g., interface instability and dendrite growth. In this work, nano silica aerogel was employed to generate a hybrid film with high lithium ion conductivity (0.6 mS cm⁻¹ at room temperature) via an in situ crosslinking reaction. TOF-SIMS profile analysis has revealed conversion mechanism of hybrid film to Li–Si alloy/LiF biphasic interface layer, suggesting that the Li–Si alloy and LiF-rich interface layer promoted rapid Li⁺ transport and shielded the Li anodes from corrosive reactions with electrolyte-derived products. When coupled with nickel-cobalt-manganese-based cathodes, the batteries achieve outstanding capacity retention over 1000 cycles at 1 C. Additionally the developed film coated on Li enabled high coulombic efficiency (99.5%) after long-term cycling when coupled with S cathodes. Overall, the results presented herein confirm an effective strategy for the development of high-energy batteries.

Hydrothermal carbonization (HTC) of lignocellulosic biomass is a promising technology for the production of carbon materials with negative carbon emissions. However, the high reaction temperature and energy consumption have limited the development of HTC technology. In conventional batch reactors, the temperature and pressure are typically coupled at saturated states. In this study, a decoupled temperature and pressure hydrothermal (DTPH) reaction system was developed to decrease the temperature of the HTC reaction of lignocellulosic biomass (rice straw and poplar leaves). The properties of hydrochars were analyzed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analyzer (TGA), etc. to propose the reaction mechanism. The results showed that the HTC reaction of lignocellulosic biomass could be realized at a low temperature of 200 °C in the DTPH process, breaking the temperature limit (230 °C) in the conventional process. The DTPH method could break the barrier of the crystalline structure of cellulose in the lignocellulosic biomass with high cellulose content, realizing the carbonization of cellulose and hemicellulose with the dehydration, unsaturated bond formation, and aromatization. The produced hydrochar had an appearance of carbon microspheres, with high calorific values, abundant oxygen-containing functional groups, a certain degree of graphitization, and good thermal stability. Cellulose acts not only as a barrier to protect itself and hemicellulose from decomposition, but also as a key precursor for the formation of carbon microspheres. This study shows a promising method for synthesizing carbon materials from lignocellulosic biomass with a carbon-negative effect.

Disulfide zirconium (ZrS₂) is a two-dimensional (2D) transition metal disulfide and has given rise to extensive attention because of its distinctive electronic structure and properties. However, mass production of high quality of ZrS₂ nanosheets to realize their practical application remains a challenge. Here, we have successfully exfoliated the bulk ZrS₂ powder with the thickness of micron into single and few-layer nanosheets through liquid-phase exfoliation in N-methylpyrrolidone (NMP) assisted via aliphatic amines as intercalators. It is found that the exfoliation yield is as high as 27.3%, which is the record value for the exfoliation of ZrS₂ nanosheets from bulk ZrS₂ powder, and 77.1% of ZrS₂ nanosheets are 2–3 layers. The molecular geometric size and aliphatic amine basicity have important impact on the exfoliation. Furthermore, the ZrS₂ nanosheets have been used as catalyst in the electrocatalytic dinitrogen reduction with the NH₃ yield of 57.75 μg h⁻¹ mg_cat.⁻¹, which is twice that by ZrS₂ nanofibers reported in literature and three times that by the bulk ZrS₂ powder. Therefore, the liquid phase exfoliation strategy reported here has great potential in mass production of ZrS₂ nanosheets for high activity electrocatalysis.

Developing multifunctional energy storage systems with high specific energy, high specific power and long cycling life has been the one of the most important research directions. Compared to batteries and traditional capacitors, supercapacitors possess more balanced performance with both high specific power and long cycle-life. Nevertheless, regular supercapacitors can only achieve energy storage without harvesting energy and the energy density is still not very high compared to batteries. Therefore, combining high specific energy and high specific power, long cycle-life and even fast self-charging into one cell has been a promising direction for future energy storage devices. The multifunctional hybrid supercapacitors like asymmetric supercapacitors, batteries/supercapacitors hybrid devices and self-charging hybrid supercapacitors have been widely studied recently. Carbon based electrodes are common materials used in all kinds of energy storage devices due to their fabulous electrical and mechanical properties. In this survey, the research progress of all kinds of hybrid supercapacitors using multiple effects and their working mechanisms are briefly reviewed. And their advantages and disadvantages are discussed. The hybrid supercapacitors have great application potential for portable electronics, wearable devices and implantable devices in the future.

Electrocatalytic splitting of water by means of renewable energy as the electricity supply is one of the most promising methods for storing green renewable energy as hydrogen. Although two-thirds of the earth's surface is covered with water, there is inadequacy of freshwater in most parts of the world. Hence, splitting seawater instead of freshwater could be a truly sustainable alternative. However, direct seawater splitting faces challenges because of the complex composition of seawater. The composition, and hence, the local chemistry of seawater may vary depending on its origin, and in most cases, tracking of the side reactions and standardizing and customizing the catalytic process will be an extra challenge. The corrosion of catalysts and competitive side reactions due to the presence of various inorganic and organic pollutants create challenges for developing stable electro-catalysts. Hence, seawater splitting generally involves a two-step process, i.e., purification of seawater using reverse osmosis and then subsequent fresh water splitting. However, this demands two separate chambers and larger space, and increases complexity of the reactor design. Recently, there have been efforts to directly split seawater without the reverse osmosis step. Herein, we represent the most recent innovative approaches to avoid the two-step process, and compare the potential application of membrane-assisted and membrane-less electrolyzers in direct seawater splitting (DSS). We particularly discuss the device engineering, and propose a novel electrolyzer design strategies for concentration gradient based membrane-less microfluidic electrolyzer.