编译 | 冯维维

Science, Volume 381, Issue 6655, 21 Jul 2023

《科学》2023年7月21日，第381卷，6655期

化学Chemistry

In situ photocatalytically enhanced thermogalvanic cells for electricity and hydrogen production

用于发电和制氢的原位光催化增强型热原电池

▲ 作者：Yijin Wang, Youzi Zhang, Xu Xin, Jiabao Yang, Maohuai Wang, Ruiling Wang, Peng Guo, Wenjing Huang, Ana Jorge Sobrido, and Xuanhua Li

▲ 链接：

https://www.science.org/doi/10.1126/science.adg0164

▲ 摘要：

高性能热电电池具有将热能转化为电能的潜力，但其效率受到氧化还原离子浓度差低的限制。研究者报道了一种原位光催化增强氧化还原反应，该反应产生氢和氧，以实现热电器件中氧化还原离子的连续浓度梯度。热功率与产氢率之间的线性关系是装置设计的基本原则。

该系统的热功率为8.2毫伏/开尔文，太阳能制氢效率高达0.4%。由36个单元组成的大面积发电机（112平方厘米）在室外运行6小时后，产生了4.4伏的开路电压和20.1毫瓦的功率，以及0.5毫摩尔的氢气和0.2毫摩尔的氧气。

▲ Abstract：

High-performance thermogalvanic cells have the potential to convert thermal energy into electricity, but their effectiveness is limited by the low concentration difference of redox ions. We report an in situ photocatalytically enhanced redox reaction that generates hydrogen and oxygen to realize a continuous concentration gradient of redox ions in thermogalvanic devices. A linear relation between thermopower and hydrogen production rate was established as an essential design principle for devices. The system exhibited a thermopower of 8.2 millivolts per kelvin and a solar-to-hydrogen efficiency of up to 0.4%. A large-area generator (112 square centimeters) consisting of 36 units yielded an open-circuit voltage of 4.4 volts and a power of 20.1 milliwatts, as well 0.5 millimoles of hydrogen and 0.2 millimoles of oxygen after 6 hours of outdoor operation.

Fluorochemicals from fluorspar via a phosphate-enabled mechanochemical process that bypasses HF

绕过氟化氢，通过磷酸盐激活机械化学过程从萤石中提取氟化学品

▲ 作者：CALUM PATEL, EMY ANDRé-JOYAUX, JAMIE A. LEITCH, XABIER MARTíNEZ DE IRUJO-LABALDE, FRANCESCO IBBA, JOB STRUIJS, MATHIAS A. ELLWANGER, ROBERT PATON, DUNCAN L. BROWNE, AND VéRONIQUE GOUVERNEUR

▲ 链接：

https://www.science.org/doi/10.1126/science.adi1557

▲ 摘要：

所有含氟化学物质——包括元素氟和亲核、亲电和自由基氟化试剂——都是由氟化氢（HF）制备的。这种剧毒和腐蚀性气体是由酸级氟石（>97% CaF2）与硫酸在恶劣条件下反应产生的。

通过绕过氟化氢的工艺使用萤石生产含氟化学品是非常可取的，但由于CaF2的不溶性，这仍然是一个未解决的问题。受磷酸钙生物矿化的启发，研究者公开了一种在机械化学条件下用磷酸氢二钾（K2HPO4）处理酸级萤石的方案。生成的固体可以在酒精溶剂中与亲电反应物形成碳氟键和硫氟键。

▲ Abstract：

All fluorochemicals—including elemental fluorine and nucleophilic, electrophilic, and radical fluorinating reagents—are prepared from hydrogen fluoride (HF). This highly toxic and corrosive gas is produced by the reaction of acid-grade fluorspar (>97% CaF2) with sulfuric acid under harsh conditions. The use of fluorspar to produce fluorochemicals via a process that bypasses HF is highly desirable but remains an unsolved problem because of the prohibitive insolubility of CaF2. Inspired by calcium phosphate biomineralization, we herein disclose a protocol of treating acid-grade fluorspar with dipotassium hydrogen phosphate (K2HPO4) under mechanochemical conditions. The process affords a solid composed of crystalline K3(HPO4)F and K2?xCay(PO3F)a(PO4)b, which is found suitable for forging sulfur-fluorine and carbon-fluorine bonds.

Programming correlated magnetic states with gate-controlled moiré geometry

门控磁栅几何相关磁态编程

▲ 作者：ERIC ANDERSON, FENG-REN FAN, JIAQI CAI, WILLIAM HOLTZMANN, TAKASHI TANIGUCHI, KENJI WATANABE, DI XIAO, WANG YAO, AND XIAODONG XU

▲ 链接：

https://www.science.org/doi/10.1126/science.adg4268

▲ 摘要：

控制系统的基本晶格几何结构的能力可能使新兴量子基态之间的转换成为可能。研究者报道了在菱形堆叠的二碲化钼（MoTe2）莫尔双层中，电子多体哈密顿量在蜂窝和三角形晶格几何之间的原位栅极切换，产生可切换的磁交换相互作用。在零电场下，他们观察到一个相关的铁磁绝缘体靠近一个空穴，居里温度可广泛调节，最高可达14K。

施加电场将系统转换成一个半填充的三角形晶格，具有反铁磁相互作用；进一步掺杂该层极化超晶格使反铁磁交换相互作用恢复为铁磁。研究证明了菱形堆叠MoTe2 莫尔双层是一个具有非平凡拓扑的工程相关状态的实验室。

▲ Abstract：

The ability to control the underlying lattice geometry of a system may enable transitions between emergent quantum ground states. We report in situ gate switching between honeycomb and triangular lattice geometries of an electron many-body Hamiltonian in rhombohedral (R)–stacked molybdenum ditelluride (MoTe2) moiré bilayers, resulting in switchable magnetic exchange interactions. At zero electric field, we observed a correlated ferromagnetic insulator near one hole per moiré unit cell with a widely tunable Curie temperature up to 14 K. Applying an electric field switched the system into a half-filled triangular lattice with antiferromagnetic interactions; further doping this layer-polarized superlattice tuned the antiferromagnetic exchange interaction back to ferromagnetic. Our work demonstrates R-stacked MoTe2moirés to be a laboratory for engineering correlated states with nontrivial topology.

地质学Geology

The precursory phase of large earthquakes

大地震的前兆

▲ 作者：QUENTIN BLETERY AND JEAN-MATHIEU NOCQUET

▲ 链接：

https://www.science.org/doi/10.1126/science.adg2565

▲ 摘要：

在大地震之前，断层上是否存在可观测到的前兆滑动，人们已经争论了几十年。虽然在几次大地震之前的观测被认为是前兆滑动的可能指标，但这些观测并不直接发生在地震之前，在大多数事件之前也没有看到，而且通常也没有在地震之后观测到。

研究者对GPS数据中的短期前兆滑动进行了全球搜索，总结了在90次地震（矩级≥7）前48小时内，由3026个高速率GPS时间序列测量到的位移——投影到震源前兆滑动预期的方向上。该方法揭示了破裂前约2小时长的滑动指数加速度，表明大地震始于滑动的前兆阶段，测量精度和密度的改进可以更有效地检测和监测。

▲ Abstract：

The existence of an observable precursory phase of slip on the fault before large earthquakes has been debated for decades. Although observations preceding several large earthquakes have been proposed as possible indicators of precursory slip, these observations do not directly precede earthquakes, are not seen before most events, and are also commonly observed without being followed by earthquakes. We conducted a global search for short-term precursory slip in GPS data. We summed the displacements measured by 3026 high-rate GPS time series—projected onto the directions expected from precursory slip at the hypocenter—during 48 hours before 90 (moment magnitude ≥7) earthquakes. Our approach reveals a ≈2-hour-long exponential acceleration of slip before the ruptures, suggesting that large earthquakes start with a precursory phase of slip, which improvements in measurement precision and density could more effectively detect and possibly monitor.

Deglaciation of northwestern Greenland during Marine Isotope Stage 11

海洋同位素阶段11期间格陵兰岛西北部的消冰作用

▲ 作者：ANDREW J. CHRIST, TAMMY M. RITTENOUR, PAUL R. BIERMAN, BENJAMIN A. KEISLING, PAUL C. KNUTZ, TONNY B. THOMSEN, NYNKE KEULEN, JULIE C. FOSDICK, SIDNEY R. HEMMING, AND ELIZABETH K. THOMAS

▲ 链接：

https://www.science.org/doi/10.1126/science.ade4248

▲ 摘要：

对格陵兰岛西北部世纪营冰芯的冰下沉积物的测量表明，在大约40万年前的间冰期，这个地方是无冰的。研究者利用发光测年和宇宙成因核素数据表明，这些沉积物是在不到1.6万年前暴露在阳光下，在无冰条件下沉积的。

这个地方没有冰，意味着格陵兰冰盖一定造成了超过1.4米的海平面上升，相当于高海平面，当时全球平均气温与当前即将经历的人类造成的气候变暖相似。

▲ Abstract：

Measurements made on subglacial sediment from the Camp Century ice core in northwestern Greenland show that the location was ice free during the interglacial that occurred around 400,000 years ago. Christ et al. used luminescence dating and cosmogenic nuclide data to show that the sediment was deposited under ice-free conditions after having been exposed at the surface to sunlight fewer than 16,000 years earlier. The absence of ice at that location means that the Greenland Ice Sheet must have contributed more than 1.4 meters of sea-level equivalent to the high sea-level stand, when the average global air temperature was similar to what we will soon experience because of human-caused climate warming.

微生物MicroBiology

Emergent coexistence in multispecies microbial communities

多物种微生物群落的共存

▲ 作者：CHANG-YU CHANG, DJORDJE BAJI?, JEAN C. C. VILA, SYLVIE ESTRELA, AND ALVARO SANCHEZ

▲ 链接：

https://www.science.org/doi/10.1126/science.adg0727

▲ 摘要：

了解维持微生物的生物多样性机制是生态学的关键愿望。过去关于微生物共存的研究主要集中在物种对上，但尚不清楚在多物种群落中是否需要孤立的成对共存。为了解决这个问题，研究者在体外对12个不同富集群落中稳定共存的成员进行了数百次成对竞争实验。

为了确定这些实验的结果，他们开发了一个自动图像分析管道来量化物种丰度。研究发现，竞争排斥是最常见的结果，它具有很强的层次性和可传递性。

由于在稳定的多物种群落中共存的许多物种在相同条件下无法在成对共培养中共存，并就此得出结论，多物种共存是一种紧急现象。这项研究强调了所在社会背景对理解复杂生态系统中共存起源的重要性。

▲ Abstract：

Understanding the mechanisms that maintain microbial biodiversity is a critical aspiration in ecology. Past work on microbial coexistence has largely focused on species pairs, but it is unclear whether pairwise coexistence in isolation is required for coexistence in a multispecies community. To address this question, we conducted hundreds of pairwise competition experiments among the stably coexisting members of 12 different enrichment communities in vitro. To determine the outcomes of these experiments, we developed an automated image analysis pipeline to quantify species abundances. We found that competitive exclusion was the most common outcome, and it was strongly hierarchical and transitive. Because many species that coexist within a stable multispecies community fail to coexist in pairwise co-culture under identical conditions, we concluded that multispecies coexistence is an emergent phenomenon. This work highlights the importance of community context for understanding the origins of coexistence in complex ecosystems.