Explore the vast range of titles available.

Carbon-free hydrogen as a promising clean energy source can be produced with electrocatalysts via water electrolysis. Oxygen evolution reaction (OER) as anodic reaction determines the overall efficiency of water electrolysis due to sluggish OER kinetics. Thus, it’s much desirable to explore the efficient and earth-abundant transition-metal-based OER electrocatalysts with high current density and superior stability for industrial alkaline electrolyzers. Herein, we demonstrate a significant enhancement of OER kinetics with the hybrid electrocatalyst arrays in alkaline via judiciously combining earth-abundant and ultrathin NiCo-based layered double hydroxide (NiCo LDH) nanosheets with nickel cobalt sulfides (NiCoS) with a facile metal-organic framework (MOF)-template-involved surface sulfidation process. The obtained NiCo LDH/NiCoS hybrid arrays exhibits an extremely low OER overpotential of 308 mV at 100 mA·cm −2 , 378 mV at 200 mA·cm −2 and 472 mV at 400 mA·cm −2 in 1 M KOH solution, respectively. A much low Tafel slope of 48 mV·dec −1 can be achieved. Meanwhile, with the current density from 50 to 250 mA·cm −2 , the NiCo-LDH/NiCoS hybrid arrays can run for 25 h without any degradation. Our results demonstrate that the construction of hybrid arrays with abundant interfaces of NiCo LDH/NiCoS can facilitate OER kinetics via possible modulation of binding energy of O-containing intermediates in alkaline media. The present work would pave the way for the development of low-cost and efficient OER catalysts and industrial application of water alkaline electrolyzers.

High-grade epithermal Au–Ag veins of the Vodorazdelnaya district in far eastern Russia are hosted by Early Cretaceous volcanic rocks of the Tytylveem belt. The largest deposit is Zone 37, a 1-km long, northeast-striking vein that is up to 35-m wide, containing at least 32 t Au. The main shoot consists of crustiform—colloform banded quartz-chalcedony-adularia-sulfide veins, of low-sulfidation style. The vein is cut by late-mineral rhyolite sills and dikes. Zone 37 vein is dated at 117 ± 2 Ma, overlapping within error with the cross-cutting rhyolites (121–119 Ma) and with intrusions of the nearby Ilirney granitic pluton (119–117 Ma). The volcanic host rocks are dated at 121–115 Ma. At September Northeast, 15 km west-northwest of Zone 37, mineralisation consists of veins up to 4 m wide, with crustiform banded quartz ± chalcedony ± adularia ± chlorite, and Zn-Pb-Cu sulfides, of intermediate sulfidation style, in a 1-km-long, north-northeast striking trend. High grades are associated with gold dendrites in fine-grained quartz bands and with minor late-stage tellurides. The veins were disrupted by intrusion of rhyolite dikes and associated phreatic breccias. Some breccias host mineralisation as vein clasts and minor matrix sulfides. The Tytylveem belt is preserved below a regional unconformity that forms the base to the overlying Late Cretaceous (106–77 Ma) Okhotsk-Chukotka Volcanic Belt (OCVB). Intrusive rocks attributed to OCVB magmatism were emplaced at about 96 Ma and are associated with overprinting hydrothermal alteration, sub-economic veins and thermal resetting of some vein adularia ages at Zone 37, to 91–97 Ma.

The development of low cost, efficient and stable overall water splitting electrocatalysts is essential for green hydrogen production. In this work, we report a defect-rich MoS2/CoS2 heterostructure supported on in situ formed graphene layers (MoS2/CoS2/C) synthesized via gas-phase sulfidation, which enables bifunctionality towards electrocatalytic oxygen evolution and hydrogen evolution reactions (OER and HER). In alkaline medium, the catalyst exhibited overpotentials of 170 mV and 293 mV for HER and OER, respectively. In an alkaline electrolyzer using MoS2/CoS2/C as both cathode and anode, a cell voltage of 1.68 V was delivered at a current density of 10 mA cm−2, and remarkable stability maintained during 20 h of chronoamperometry test. Furthermore, the Faraday efficiencies of HER and OER in electrolytic water systems are as high as 97.3% and 94.7%, respectively. The good HER and OER catalytic activity over the MoS2/CoS2/C catalyst could be attributed to the abundance of defects, the strong interaction between MoS2 and CoS2, the large electrochemical surface area, and the excellent electron conductivity. Therefore, this work may provide an effective strategy for future development of overall water splitting catalysts.

Saltwater intrusion is the leading edge of sea-level rise, preceding tidal inundation, but leaving its salty signature far inland. With climate change, saltwater is shifting landward into regions that previously have not experienced or adapted to salinity, leading to novel transitions in biogeochemistry, ecology, and human land uses. We explore these changes and their implications for climate adaptation in coastal ecosystems. Biogeochemical changes, including increases in ionic strength, sulfidation, and alkalinization, have cascading ecological consequences such as upland forest retreat, conversion of freshwater wetlands, nutrient mobilization, and declines in agricultural productivity. We explore the trade-offs among land management decisions in response to these changes and how public policy should shape socioecological transitions in the coastal zone. Understanding transitions resulting from saltwater intrusion—and how to manage them—is vital for promoting coastal resilience.

The world reserves of oxidized lead–zinc ores are large, but their processing faces significant difficulties due to their refractory nature. This paper presents a novel approach to the preparation of refractory oxidized lead ores for flotation. The proposed method is based on the co-roasting of oxidized lead-bearing ores from the Ozernoye polymetallic deposit (Western Transbaikalia, Russia) with fine-grained sulfide lead–zinc ore sourced from the same deposit and the addition of calcium oxide. This method allows for the activation of mineral complexes, the sulfidation of oxidized lead–zinc minerals, and the minimization of the amount of sulfur dioxide gas emitted. Co-roasting oxidized lead–zinc ore with sulfide ore (10–30 wt. pct) at 650–700 °C has been shown to result in the selective oxidation of pyrite and sulfidation of oxidized lead and zinc minerals. The proposed method of processing polymetallic ores is capable of simultaneously involving not only oxidized lead–zinc ores but also refractory sulfide ores, thereby extending the operational lifespan of the mining enterprise and reducing the environmental impact.

Cu(OH)2 has the advantages of ease of structural regulation, good conductivity, and relatively low cost, making it a suitable candidate material for use as an electrocatalyst. However, its catalytic efficiency and stability still need to be improved further. Therefore, Cu(OH)2/Cu2S was successfully prepared on copper foam (CF) using the in situ growth and hydrothermal method. The structural characterization showed that sulfidation treatment induced transformation of Cu(OH)2/CF from smooth nanorods into a coral‐like structure, which exposed more active sites of Cu(OH)2/Cu2S and enhanced the performance of electrocatalytic hydrogen evolution reaction (HER). Compared with Cu(OH)2, Cu(OH)2/Cu2S showed better alkaline HER performance, especially when the vulcanization concentration was 0.1 M, the overpotential of Cu(OH)2/Cu2S was 174 mV, and the reaction kinetics was 64 mv dec−1 at a current density of 10 mA cm−2. In this work, the morphology and electronic structure of copper‐based metal sulfide electrocatalysts were adjusted by sulfide treatment, which provided a new reference for improving HER performance. In comparison to the smooth Cu(OH)2/CF nanorod array, the Cu(OH)2/Cu2S structure with a coral‐like morphology shows greater stability and numerous reactive sites, resulting in higher current density (10 mA cm−2) and lower overpotential (174 mV). These findings indicate that the Cu(OH)2/Cu2S structure is a more efficient catalyst for electrocatalytic hydrogen production.

Quartz veins in bonanza-type ore zones of low-sulfidation epithermal deposits frequently contain ore mineral dendrites. Gold and naumannite dendrites hosted by colloform silica bands from four deposits located in California and Nevada were studied to better understand the processes by which these delicate ore mineral aggregates are formed. High-magnification optical petrography revealed that the colloform bands hosting the ore mineral dendrites originally consisted of non-crystalline silica microspheres. Textural relationships suggest that the microspherical silica provided the structural framework for the delicate ore mineral aggregates to grow. The ore mineral dendrites either grew contemporaneously with the deposition of the microspherical silica along the vein walls or after their deposition within permeable gel-like layers of microspheres. Etching in hydrofluoric acid showed that the ore mineral dendrites exhibit complex surface morphologies. The surface morphology of the ore mineral dendrites and their textural relationships with the silica host were modified as a result of post-depositional maturation and recrystallization causing the conversion of the non-crystalline silica to quartz. It is proposed here that ore mineral dendrites formed in low-sulfidation epithermal veins during periods of two-phase flow associated with short-lived events of vigorous boiling or flashing, which caused supersaturation of silica in the liquid and the deposition of the ore minerals.

HighlightsThe unique 0D-2D ZnS nanodots/Ti3C2Tx MXene hybrids with strong interfacial interaction enable to achieve stable cyclability and excellent rate performance for lithium storage.The lithium storage mechanism of ZnS is clarified and new insights into phase transition mechanism are proposed.The strong interfacial interaction between ZnS nanodots and MXene nanosheets at the ZnS-MXene heterointerface exhibits high lithium adsorption capability, enhanced interfacial electron transfer, and low lithium diffusion energy barrier.ZnS has great potentials as an anode for lithium storage because of its high theoretical capacity and resource abundance; however, the large volume expansion accompanied with structural collapse and low conductivity of ZnS cause severe capacity fading and inferior rate capability during lithium storage. Herein, 0D-2D ZnS nanodots/Ti3C2Tx MXene hybrids are prepared by anchoring ZnS nanodots on Ti3C2Tx MXene nanosheets through coordination modulation between MXene and MOF precursor (ZIF-8) followed with sulfidation. The MXene substrate coupled with the ZnS nanodots can synergistically accommodate volume variation of ZnS over charge–discharge to realize stable cyclability. As revealed by XPS characterizations and DFT calculations, the strong interfacial interaction between ZnS nanodots and MXene nanosheets can boost fast electron/lithium-ion transfer to achieve excellent electrochemical activity and kinetics for lithium storage. Thereby, the as-prepared ZnS nanodots/MXene hybrid exhibits a high capacity of 726.8 mAh g−1 at 30 mA g−1, superior cyclic stability (462.8 mAh g−1 after 1000 cycles at 0.5 A g−1), and excellent rate performance. The present results provide new insights into the understanding of the lithium storage mechanism of ZnS and the revealing of the effects of interfacial interaction on lithium storage performance enhancement.

The atmospheres of small exoplanets likely derive from a combination of geochemical outgassing and primordial gases left over from formation. Secondary atmospheres, such as those of Earth, Mars, and Venus, are sourced by outgassing. Persistent outgassing into long-lived, primordial, hydrogen–helium envelopes produces hybrid atmospheres of which there are no examples in the solar system. We construct a unified theoretical framework for calculating the outgassing chemistry of both secondary and hybrid atmospheres, where the input parameters are the surface pressure, oxidation, and sulfidation states of the mantle, as well as the primordial atmospheric hydrogen, helium, and nitrogen content. Nonideal gases (quantified by the fugacity coefficient) and nonideal mixing of gaseous components (quantified by the activity coefficient) are considered. Both secondary and hybrid atmospheres exhibit a rich diversity of chemistries, including hydrogen-dominated atmospheres. The abundance ratio of carbon dioxide to carbon monoxide serves as a powerful diagnostic for the oxygen fugacity of the mantle, which may conceivably be constrained by James Webb Space Telescope spectra in the near future. Methane-dominated atmospheres are difficult to produce and require specific conditions: atmospheric surface pressures exceeding ∼10 bar, a reduced (poorly oxidized) mantle, and diminished magma temperatures (compared to modern Earth). Future work should include photochemistry in these calculations and clarify the general role of atmospheric escape. Exoplanet science should quantify the relationship between the mass and oxygen fugacity for a sample of super Earths and sub-Neptunes; such an empirical relationship already exists for solar system bodies.