Search Results (8)

Cobalt telluride (CoTe₂) is considered an advanced anode material for sodium-ion batteries (SIBs) because of its high theoretical capacity and high conductivity. Nevertheless, the ionic radius of the Co²⁺ ion (0.74 Å) is smaller than that of the Na⁺ ion, meaning the integrity of CoTe₂ electrodes can be easily damaged when Na⁺ ions diffuse into CoTe₂ and convert to large Na₂Te. Herein, we propose a doping strategy by introducing an unreactive element but with a large radius to enhance the overall performance. Lanthanum (La) can be doped into the CoTe₂ structure to counteract the size effect of Na₂Te since La has a large radius. On the other hand, La with abundant electrons in CoTe₂ can also facilitate the charge transfer during charge/discharge. As a result, La-doped CoTe₂ (La-CoTe₂) can deliver a maximum capacity of 345 mAh g⁻¹ at 0.05 A g⁻¹ and has a decent rate performance. After 2000 cycles at 2 A g⁻¹, a capacity of 88 mAh g⁻¹ remained, which is a notable improvement compared to undoped CoTe₂. These results demonstrate the potential of rare earth elements in preparing advanced SIB electrode materials. Full article

A mixed-metal ternary chalcogenide, cobalt molybdenum telluride (CMT), has been identified as an efficient tri-functional electrocatalyst for seawater splitting, leading to enhanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). The CMT was synthesized by a single step hydrothermal technique. Detailed electrochemical studies of the CMT-modified electrodes showed that CMT has a promising performance for OER in the simulated seawater solutions, exhibiting a small overpotential of 385 mV at 20 mA cm⁻², and superior catalyst durability for prolonged period of continuous oxygen evolution. Interestingly, while gas chromatography analysis confirmed the evolution of oxygen in an anodic chamber, it showed that there was no chlorine evolution from these electrodes in alkaline seawater, highlighting the novelty of this catalyst. CMT also displayed remarkable ORR activity in simulated seawater as indicated by its four-electron reduction pathway forming water as the dominant product. One of the primary challenges of seawater splitting is chlorine evolution from the oxidation of dissolved chloride salts. The CMT catalyst successfully and significantly lowers the water oxidation potential, thereby separating the chloride and water oxidation potentials by a larger margin. These results suggest that CMT can function as a highly active tri-functional electrocatalyst with significant stability, making it suitable for clean energy generation and environmental applications using seawater. Full article

Mineral assemblages containing Cu-Bi sulfosalts, Bi chalcogenides, and Ag-(Au) tellurides have been identified in the mid-Miocene Zhibula Cu skarn deposit, Gangdese Belt, southern Tibet. Different mineral assemblages from three locations in the deposit, including proximal massive garnet skarn, proximal retrogressed pyroxene-dominant skarn in contact with marble, and distal banded garnet–pyroxene skarn hosted in marble, are studied to constrain the evolution of the mineralization. Hypogene bornite contains elevated Bi (mean 6.73 wt.%) and co-exists in proximal andradite skarn with a second bornite with far lower Bi content, carrollite, Au-Ag tellurides (hessite, petzite), and wittichenite. This assemblage indicates formation at relatively high temperatures (>400 °C) and high f_S2 and f_Te2 during prograde-stage mineralization. Assemblages of Bi sulfosalts (wittichenite, aikinite, kupčíkite, and paděraite) and bismuth chalcogenides (e.g., tetradymite) in proximal pyroxene skarn are also indicative of formation at relatively high temperatures, but at relatively lower f_Te2 and f_S2 conditions. Within the reduced distal skarn (chalcopyrite–pyrrhotite-bearing) in marble, cobalt, and nickel occur as discrete minerals: cobaltite, melonite and cobaltic pentlandite. The trace ore mineral signature of the Zhibula skarn and the distributions of precious and critical trace elements such as Ag, Au, Co, Te, Se, and Bi support an evolving magmatic–hydrothermal system in which different parts of the deposit each define ore formation at distinct local physicochemical conditions. This is the first report of kupčíkite and paděraite from a Chinese location. Their compositions are comparable to other occurrences, but conspicuously, they do not form nanoscale intergrowths with one another. Full article

The interest in the Spark Plasma Sintering (SPS) technique has continuously increased over the last few years. This article shows the possibility of the development of an SPS device used for material processing and synthesis in both scientific and industrial applications and aims to present manufacturing methods and the versatility of an SPS device, presenting examples of processing Arc-Melted- (half-Heusler, cobalt triantimonide) and Self-propagating High-temperature Synthesis (SHS)-synthesized semiconductor (bismuth telluride) materials. The SPS system functionality development is presented, the purpose of which was to broaden the knowledge of the nature of SPS processes. This approach enabled the precise design of material sintering processes and also contributed to increasing the repeatability and accuracy of sintering conditions. Full article

Transition metal selenides have narrow or zero band-gap characteristics and high theoretical specific capacity. Among them, cobalt selenide and cobalt telluride have some typical problems such as large volume changes, low conductivity, and poor structural stability, but they have become a research hotspot in the field of energy storage and conversion because of their high capacity and high designability. Some of the innovative synthesis, doping, and nanostructure design strategies for CoSe_x and CoTe_x, such as CoSe-InCo-InSe bimetallic bi-heterogeneous interfaces, CoTe anchoring MXenes, etc., show great promise. In this paper, the research progress on the multistep transformation mechanisms of CoSe_x and CoTe_x is summarized, along with advanced structural design and modification methods such as defect engineering and compositing with MXenes. It is hoped that this review will provide a glimpse into the development of CoSe_x and CoTe_x anodes for alkali-ion batteries. Full article

Mineralization of Te and Se was found in gold deposits and uranium occurrences, located in the Paleoproterozoic greenstone belts in Northern Fennoscandia. These deposits are of different genesis, but all of them formed at the late stages of the Svecofennian orogeny, and they have common geochemical association of metals Au, Cu, Co, U, Bi, Te, and Se. The prevalent Te minerals are Ni and Fe tellurides melonite and frohbergite, and Pb telluride altaite. Bismuth tellurides were detected in many deposits in the region, but usually not more than in two–three grains. The main selenide in the studied deposits is clausthalite. The most diversified selenium mineralization (clausthalite, klockmannite, kawazulite, skippenite, poubaite) was discovered in the deposits, located in the Russian part of the Salla-Kuolajarvi belt. Consecutive change of sulfides by tellurides, then by selenotellurides and later by selenides, indicates increase of selenium fugacity, fSe₂, in relation to fTe₂ and to fS₂in the mineralizing fluids. Gold-, selenium-, and tellutium-rich fluids are potentially linked with the post-Svecofennian thermal event and intrusion of post-orogenic granites (1.79–1.75 Ga) in the Salla-Kuolajarvi and Perapohja belts. Study of fluid inclusions in quartz from the deposits in the Salla-Kuolajarvi belt showed that the fluids were high-temperature (240–300 °C) with high salinity (up to 26% NaCl-eq.). Composition of all studied selenotellurides, kawazulite-skippenite, and poubaite varies significantly in Se/Te ratio and in Pb content. Skippenite and kawazulite show the full range of Se-Te isomorphism. Ni-Co and Co-Fe substitution plays an important role in melonite and mattagamite: high cobalt was detected in nickel telluride in the Juomasuo and Konttiaho, and mattagamites from Ozernoe and Juomasuo contain significant Fe. In the Ozernoe uranium occurrence, the main mineral-concentrator of selenium is molybdenite, which contains up to 16 wt.% of Se in the marginal parts of the grains. The molybdenite is rich in Re (up to 1.2 wt.%), and the impurity of Re is irregularly distributed in molybdenite flakes and spherulites. Full article

Solar energy conversion through photoelectrochemical water splitting (PEC) is an upcoming promising technique. MoS₂/CoTe heterostructures were successfully prepared and utilized for PEC studies. MoS₂ and CoTe were prepared by a hydrothermal method which were then ultrasonicated with wt. % ratios of 1:3, 1:1 and 3:1 to prepare MoS₂/CoTe (1:3), MoS₂/CoTe (1:1) and MoS₂/CoTe (3:1) heterostructure, respectively. The pure materials and heterostructures were characterized by XRD, UV–vis-DRS, SEM, XPS, PL and Raman spectroscopy. Photoelectrochemical measurements were carried out by linear sweep voltammetry and electrochemical impedance spectroscopic measurements. A maximum photocurrent density of 2.791 mA/cm² was observed for the MoS₂/CoTe (1:1) heterojunction which is about 11 times higher than the pristine MoS₂. This current density was obtained at an applied bias of 0.62 V vs. Ag/AgCl (1.23 V vs. RHE) under the light intensity of 100 mW/cm² of AM 1.5G illumination. The enhanced photocurrent density may be attributed to the efficient electron–hole pair separation. The solar to hydrogen conversion efficiency was found to be 0.84% for 1:1 MoS₂/CoTe, signifying the efficient formation of the p-n junction. This study offers a novel heterojunction photocatalyst, for PEC water splitting. Full article