Nature, 8 Feb. 2024, VOL 626, ISSUE 7998
《自然》2024年2月8日，第626卷，7998期
天文學Astronomy
A recently formed ocean inside Saturn’s moon Mimas
土衛(wèi)一內部最近形成的海洋
▲ 作者：V. Lainey, N. Rambaux, G. Tobie, N. Cooper, Q. Zhang, B. Noyelles, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06975-9
▲ 摘要：
可能孕育海洋的衛(wèi)星正逐漸成為太陽系中相對常見的物體。這些長壽命海洋的存在通常因內部動力學引起的表面變化而暴露。因此，土衛(wèi)一將是最不可能找到海洋存在的地方。
根據卡西尼號數據對土衛(wèi)一軌道運動（特別是土衛(wèi)一的近日點漂移）的詳細分析，研究組表明土衛(wèi)一坑坑洼洼的冰殼內隱藏著一個全球海洋，深度為20~30千米。偏心阻尼意味著該海洋的年齡可能不到2500萬年，而且還在不斷進化。
該模型顯示，直到最近（不到2~3百萬年前）海洋-冰界面的深度才達到不足30千米，時間跨度太短，尚未出現土衛(wèi)一表面活動的跡象。
▲ Abstract：
Moons potentially harbouring a global ocean are tending to become relatively common objects in the Solar System. The presence of these long-lived global oceans is generally betrayed by surface modification owing to internal dynamics. Hence, Mimas would be the most unlikely place to look for the presence of a global ocean. Here, from detailed analysis of Mimas’s orbital motion based on Cassini data, with a particular focus on Mimas’s periapsis drift, we show that its heavily cratered icy shell hides a global ocean, at a depth of 20–30?kilometres. Eccentricity damping implies that the ocean is likely to be less than 25?million years old and still evolving. Our simulations show that the ocean–ice interface reached a depth of less than 30?kilometres only recently (less than 2–3?million years ago), a time span too short for signs of activity at Mimas’s surface to have appeared.
材料科學Materials Science
Stable blue phosphorescent organic LEDs that use polariton-enhanced Purcell effects
使用極化激元增強的珀塞爾效應來穩(wěn)定藍色磷光有機LED
▲ 作者：Haonan Zhao, Claire E. Arneson, Dejiu Fan & Stephen R. Forrest
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06976-8
▲ 摘要：
磷光有機發(fā)光二極管（PHOLEDs）具有高效率、亮度和顏色可調性，適用于顯示器和照明應用。然而，克服藍色PHOLED的短工作壽命仍然是有機電子領域最具挑戰(zhàn)性的高值問題之一。其短壽命源于高能、長壽命的藍色三重態(tài)湮滅導致的分子離解。
珀塞爾效應，即微腔中輻射衰減率的增強，可降低三重態(tài)密度，從而降低破壞性高能三重態(tài)-極化子湮滅（TPA）和三重態(tài)-三重態(tài)湮滅（TTA）事件的概率。
研究組介紹了藍色PHOLED中極化子增強的珀塞爾效應。結果發(fā)現，等離子-激子極化激元（PEPs）顯著增加了珀塞爾效應的強度，在藍色PHOLED內50 nm厚的發(fā)射層（EML）中，平均珀塞爾因子（PF）達到2.4±0.2。與傳統(tǒng)PHOLED中的應用相比，青色發(fā)光Ir復合物器件的LT90（PHOLED亮度衰減到其初始值90%的時間）提高了5.3倍。
將色度坐標（0.14、0.14）和（0.15、0.20）轉換為深藍色，珀塞爾增強器件與類似的深藍色PHOLED相比壽命提升了10~14倍，其中一種結構達到了迄今為止報道的最長Ir復合物器件壽命LT90 = 140±20小時。極化激元增強的珀塞爾效應和微腔工程為延長深藍色PHOLED壽命提供了新的可能性。
▲ Abstract：
Phosphorescent organic light-emitting diodes (PHOLEDs) feature high efficiency, brightness and colour tunability suitable for both display and lighting applications. However, overcoming the short operational lifetime of blue PHOLEDs remains one of the most challenging high-value problems in the field of organic electronics. Their short lifetimes originate from the annihilation of high-energy, long-lived blue triplets that leads to molecular dissociation. The Purcell effect, the enhancement of the radiative decay rate in a microcavity, can reduce the triplet density and, hence, the probability of destructive high-energy triplet–polaron annihilation (TPA) and triplet–triplet annihilation (TTA) events. Here we introduce the polariton-enhanced Purcell effect in blue PHOLEDs. We find that plasmon–exciton polaritons (PEPs) substantially increase the strength of the Purcell effect and achieve an average Purcell factor (PF) of 2.4?±?0.2 over a 50-nm-thick emission layer (EML) in a blue PHOLED. A 5.3-fold improvement in LT90 (the time for the PHOLED luminance to decay to 90% of its initial value) of a cyan-emitting Ir-complex device is achieved compared with its use in a conventional PHOLED. Shifting the chromaticity coordinates to (0.14,?0.14) and (0.15,?0.20) into the deep blue, the Purcell-enhanced devices achieve 10–14 times improvement over similarly deep-blue PHOLEDs, with one structure reaching the longest Ir-complex device lifetime of LT90?=?140?±?20?h reported so far. The polariton-enhanced Purcell effect and microcavity engineering provide new possibilities for extending deep-blue PHOLED lifetimes.
A rechargeable calcium–oxygen battery that operates at room temperature
在室溫下運行的可充電鈣氧電池
▲ 作者：Lei Ye, Meng Liao, Kun Zhang, Mengting Zheng, Yi Jiang, Xiangran Cheng, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06949-x
▲ 摘要：
鈣氧（Ca-O2）電池理論上可通過將O2還原為氧化鈣化合物（CaOx），以低成本提供高容量。然而，由于CaOx/O2化學通常涉及惰性放電產物，且很少有電解質能夠兼顧高度還原性的Ca金屬陽極和O2，在室溫下運行的可充電Ca-O2電池尚未實現。
研究組報道了一種在室溫下可充電700次的Ca-O2電池。該電池依靠高度可逆的雙電子氧化還原來形成化學反應性過氧化鈣（CaO2）作為放電產物。使用耐用的離子液體基電解質，通過在室溫下促進Ca金屬陽極中的Ca電鍍-剝離和改善空氣陰極中的CaO2/O2氧化還原，研究組實現了這種雙電子反應。
該研究所提出的Ca-O2電池在空氣中很穩(wěn)定，可制成柔性纖維，編織成紡織電池用于下一代可穿戴系統(tǒng)。
▲ Abstract：
Calcium–oxygen (Ca–O2) batteries can theoretically afford high capacity by the reduction of O2 to calcium oxide compounds (CaOx) at low cost. Yet, a rechargeable Ca–O2 battery that operates at room temperature has not been achieved because the CaOx/O2 chemistry typically involves inert discharge products and few electrolytes can accommodate both a highly reductive Ca metal anode and O2. Here we report a Ca–O2 battery that is rechargeable for 700 cycles at room temperature. Our battery relies on a highly reversible two-electron redox to form chemically reactive calcium peroxide (CaO2) as the discharge product. Using a durable ionic liquid-based electrolyte, this two-electron reaction is enabled by the facilitated Ca plating–stripping in the Ca metal anode at room temperature and improved CaO2/O2 redox in the air cathode. We show the proposed Ca–O2 battery is stable in air and can be made into flexible fibres that are weaved into textile batteries for next-generation wearable systems.
化學Chemistry
Recovery of isolated lithium through discharged state calendar ageing
通過放電狀態(tài)日歷老化恢復死鋰
▲ 作者：Wenbo Zhang, Philaphon Sayavong, Xin Xiao, Solomon T. Oyakhire, Sanzeeda Baig Shuchi, Rafael A. Vilá, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06992-8
▲ 摘要：
可充電鋰金屬電池的比能量有望比最先進的可充電鋰離子電池提升一倍以上，使鋰金屬電池成為下一代高能電池技術的首選。然而，與鋰離子電池相比，當前鋰金屬電池存在快速循環(huán)衰減的問題，阻礙了其實際應用。容量衰減的一個主要原因是鋰與電化學回路斷開，形成死鋰。日歷老化研究表明，在充電狀態(tài)下靜息可促進活性鋰與周圍電解質的進一步反應。
研究組發(fā)現放電狀態(tài)下的日歷老化通過死鋰恢復提高了容量保持率，這與眾所周知的在充電狀態(tài)日歷老化期間觀察到的容量衰減現象形成對比。通過使用混合連續(xù)-靜息循環(huán)方案和滴定氣相色譜法觀察到Li||Cu半電池和無陽極電池的庫侖效率均大于100%，驗證了非活性容量恢復。
原位光學裝置進一步證實了過量的死鋰再活化是容量恢復增加的主要因素。通過放電狀態(tài)靜息來恢復容量的途徑此前從未報道，該研究強調了循環(huán)策略對鋰金屬電池性能的顯著影響。
▲ Abstract：
Rechargeable Li-metal batteries have the potential to more than double the specific energy of the state-of-the-art rechargeable Li-ion batteries, making Li-metal batteries a prime candidate for next-generation high-energy battery technology. However, current Li-metal batteries suffer from fast cycle degradation compared with their Li-ion battery counterparts, preventing their practical adoption. A main contributor to capacity degradation is the disconnection of Li from the electrochemical circuit, forming isolated Li. Calendar ageing studies have shown that resting in the charged state promotes further reaction of active Li with the surrounding electrolyte. Here we discover that calendar ageing in the discharged state improves capacity retention through isolated Li recovery, which is in contrast with the well-known phenomenon of capacity degradation observed during the charged state calendar ageing. Inactive capacity recovery is verified through observation of Coulombic efficiency greater than 100% on both Li||Cu half-cells and anode-free cells using a hybrid continuous–resting cycling protocol and with titration gas chromatography. An operando optical setup further confirms excess isolated Li reactivation as the predominant contributor to the increased capacity recovery. These insights into a previously unknown pathway for capacity recovery through discharged state resting emphasize the marked impact of cycling strategies on Li-metal battery performance.
地球科學Earth Science
Elevated Southern Hemisphere moisture availability during glacial periods
冰川期南半球水分可用性升高
▲ 作者：Rieneke Weij, J. M. Kale Sniderman, Jon D. Woodhead, John C. Hellstrom, Josephine R. Brown, Russell N. Drysdale, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06989-3
▲ 摘要：
晚更新世冰河時期的氣候通常被描述為對中低緯度的生態(tài)系統(tǒng)施加了水分壓力。這一觀點主要基于廣泛分布的低生物量冰川植被的花粉化石證據，其被解釋為氣候干燥的跡象。然而，木本植物的生長在低大氣CO2下受到抑制，因此了解冰川環(huán)境需要開發(fā)獨立于植被的新型古氣候指標。
研究組表明，與預期相反，在過去35萬年中，南澳大利亞氣候水分可用性的峰值主要局限于冰川期，包括末次冰盛期，而溫暖的間冰期相對干燥。通過測量南半球亞熱帶地區(qū)洞穴堆積物生長的時間（如今南半球的年水分平衡主要為負），研究組開發(fā)了一個獨立于植被的氣候水分可用性記錄，并延伸貫穿多個冰期-間冰期循環(huán)。
研究結果表明，冷濕響應在整個南亞熱帶地區(qū)是一致的，部分原因可能是在寒冷冰川溫度下蒸發(fā)減少。鑒于南半球亞熱帶寒冷冰川環(huán)境被一致描述為干旱，該研究結果表明，應重新審視該時期是否在進化或生理上阻礙了動物、植物和潛在人類種群的遷徙和擴張。
▲ Abstract：
Late Pleistocene ice-age climates are routinely characterized as having imposed moisture stress on low- to mid-latitude ecosystems. This idea is largely based on fossil pollen evidence for widespread, low-biomass glacial vegetation, interpreted as indicating climatic dryness. However, woody plant growth is inhibited under low atmospheric CO2, so understanding glacial environments requires the development of new palaeoclimate indicators that are independent of vegetation. Here we show that, contrary to expectations, during the past 350?kyr, peaks in southern Australian climatic moisture availability were largely confined to glacial periods, including the Last Glacial Maximum, whereas warm interglacials were relatively dry. By measuring the timing of speleothem growth in the Southern Hemisphere subtropics, which today has a predominantly negative annual moisture balance, we developed a record of climatic moisture availability that is independent of vegetation and extends through multiple glacial–interglacial cycles. Our results demonstrate that a cool-moist response is consistent across the austral subtropics and, in part, may result from reduced evaporation under cool glacial temperatures. Insofar as cold glacial environments in the Southern Hemisphere subtropics have been portrayed as uniformly arid, our findings suggest that their characterization as evolutionary or physiological obstacles to movement and expansion of animal, plant and, potentially, human populations should be reconsidered.
Country-specific net-zero strategies of the pulp and paper industry
紙漿和造紙行業(yè)的國別凈零戰(zhàn)略
▲ 作者：Min Dai, Mingxing Sun, Bin Chen, Lei Shi, Mingzhou Jin, Yi Man, et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-023-06962-0
▲ 摘要：
全球溫室氣體排放的大部分歸因于紙漿和造紙行業(yè)。鑒于各國紙漿和造紙行業(yè)間的巨大差異，國別戰(zhàn)略對該行業(yè)到2050年實現凈零排放至關重要。
研究組對30個主要國家1961—2019年國內造紙相關部門的溫室氣體凈排放量（約占同期全球人為溫室氣體排放量的3.2%）進行了全面的自下而上評估，并通過涵蓋關鍵因素的2160種情景探討了減緩策略。
研究結果顯示，各國紙漿和造紙行業(yè)在歷史排放演變趨勢和結構方面存在實質性差異。到2050年，所有國家都可以實現其紙漿和造紙行業(yè)的凈零排放，大多數發(fā)達國家采取單一措施，大多數發(fā)展中國家采取多項措施。
除了提高能源效率和能源系統(tǒng)脫碳外，森林資源豐富的熱帶發(fā)展中國家應優(yōu)先考慮可持續(xù)森林管理，而其他發(fā)展中國家應更加重視提高甲烷捕獲率和減少循環(huán)利用。這些見解對于制定適合每個國家的凈零戰(zhàn)略以及到2050年實現紙漿和造紙行業(yè)的凈零排放至關重要。
▲ Abstract：
The pulp and paper industry is an important contributor to global greenhouse gas emissions. Country-specific strategies are essential for the industry to achieve net-zero emissions by 2050, given its vast heterogeneities across countries. Here we develop a comprehensive bottom-up assessment of net greenhouse gas emissions of the domestic paper-related sectors for 30 major countries from 1961 to 2019—about 3.2% of global anthropogenic greenhouse gas emissions from the same period—and explore mitigation strategies through 2,160 scenarios covering key factors. Our results show substantial differences across countries in terms of historical emissions evolution trends and structure. All countries can achieve net-zero emissions for their pulp and paper industry by 2050, with a single measure for most developed countries and several measures for most developing countries. Except for energy-efficiency improvement and energy-system decarbonization, tropical developing countries with abundant forest resources should give priority to sustainable forest management, whereas other developing countries should pay more attention to enhancing methane capture rate and reducing recycling. These insights are crucial for developing net-zero strategies tailored to each country and achieving net-zero emissions by 2050 for the pulp and paper industry.
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