CuFeS2 Quantum Dots Anchored in Carbon Frame: Superior Lithium Storage Performance and the Study of Electrochemical Mechanism

Sublayer-Sulfur-Vacancy-Induced Charge Redistribution of FeCuS Nanoflower Awakening Alkaline Hydrogen Evolution

Advancing the progress of sustainable and green energy technologies requires the improvement of valid electrocatalysts for the hydrogen evolution reaction (HER). Reconfiguring charge distribution through heteroatom doping-induced vacancy serves as an effective approach to implement high performance for HER catalysts. Here, we successfully fabricated Fe-doped CuS (FeCuS) with the sublayer sulfur vacancy to judge its HER performance and dissect the activity origins. Density functional theory calculation further elucidates that the primary factor contributing to the heightened HER activity is that the sublayer sulfur vacancies awaken the charge redistribution. In addition to effectively decreasing the energy barrier associated with the Volmer step, it modulates the adsorption/desorption capacity of H*. As a result, its intrinsic activity for the HER has significantly increased. Concretely, the obtained FeCuS displays an excellent catalytic performance, whose Tafel slope is only 59 mV dec-1 and the overpotential (at 10 mA cm-2) is as low as 71 mV in an alkaline environment, surpassing the majority of previously documented catalysts in scientific literature. This work shows that the construction of sublayer sulfur vacancies by Fe doping can achieve the charge redistribution and precise tuning of electronic structure; thereby, the inert CuS can be transformed into highly efficient electrocatalysts.

An olsalazine nanoneedle-embedded inulin hydrogel reshapes intestinal homeostasis in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic and refractory condition characterized by disrupted epithelial barrier, dysregulated immune balance, and altered gut microbiota. Nano-enabled interventions for restoring gut homeostasis have the potential to alleviate inflammation in IBD. Herein, we developed a combination of olsalazine (Olsa)-based nanoneedles and microbiota-regulating inulin gel to reshape intestinal homeostasis and relieve inflammation. The Olsa-derived nanoneedles exhibited reactive oxygen species scavenging ability and anti-inflammatory effects in lipopolysaccharide-simulated macrophages. The composite of nanoneedles and inulin gel (Cu2(Olsa)/Gel) displayed a macroporous structure, improved bio-adhesion, and enhanced colon retention after oral administration. Mechanistically, the composite effectively downregulated pro-inflammatory cytokine levels and promoted epithelial barrier repair through anti-inflammatory and antioxidant therapies, resulting in significant alleviation of colitis in three animal models of IBD. Furthermore, analysis of gut microbiota revealed that Cu2(Olsa)/Gel treatment increased the diversity of intestinal microflora and decreased the relative abundance of pathogenic bacteria such as Proteobacteria. Overall, this study provides a self-delivering nanodrug and dietary fiber hydrogel composite for IBD therapy, offering an efficient approach to restore intestinal homeostasis.

Selected I-III-VI2 Semiconductors: Synthesis, Properties and Applications in Photovoltaic Cells

I-III-VI2 group quantum dots (QDs) have attracted high attention in photoelectronic conversion applications, especially for QD-sensitized solar cells (QDSSCs). This group of QDs has become the mainstream light-harvesting material in QDSSCs due to the ability to tune their electronic properties through size, shape, and composition and the ability to assemble the nanocrystals on the surface of TiO2. Moreover, these nanocrystals can be produced relatively easily via cost-effective solution-based synthetic methods and are composed of low-toxicity elements, which favors their integration into the market. This review describes the methods developed to prepare I-III-VI2 QDs (AgInS2 and CuInS2 were excluded) and control their optoelectronic properties to favor their integration into QDSSCs. Strategies developed to broaden the optoelectronic response and decrease the surface-defect states of QDs in order to promote the fast electron injection from QDs into TiO2 and achieve highly efficient QDSSCs will be described. Results show that heterostructures obtained after the sensitization of TiO2 with I-III-VI2 QDs could outperform those of other QDSSCs. The highest power-conversion efficiency (15.2%) was obtained for quinary Cu-In-Zn-Se-S QDs, along with a short-circuit density (JSC) of 26.30 mA·cm-2, an open-circuit voltage (VOC) of 802 mV and a fill factor (FF) of 71%.

Mixed Cu-Fe Sulfides Derived from Polydopamine-Coated Prussian Blue Analogue as a Lithium-Ion Battery Electrode

Batteries employing transition-metal sulfides enable high-charge storage capacities, but polysulfide shuttling and volume expansion cause structural disintegration and early capacity fading. The design of heterostructures combining metal sulfides and carbon with an optimized morphology can effectively address these issues. Our work introduces dopamine-coated copper Prussian blue (CuPB) analogue as a template to prepare nanostructured mixed copper-iron sulfide electrodes. The material was prepared by coprecipitation of CuPB with in situ dopamine polymerization, followed by thermal sulfidation. Dopamine controls the particle size and favors K-rich CuPB due to its polymerization mechanism. While the presence of the coating prevents particle agglomeration during thermal sulfidation, its thickness demonstrates a key effect on the electrochemical performance of the derived sulfides. After a two-step activation process during cycling, the C-coated KCuFeS₂ electrodes showed capacities up to 800 mAh/g at 10 mA/g with nearly 100% capacity recovery after rate handling and a capacity of 380 mAh/g at 250 mA/g after 500 cycles.

CuFeS2 as a Very Stable High-Capacity Anode Material for Sodium-Ion Batteries: A Multimethod Approach for Elucidation of the Complex Reaction Mechanisms during Discharge and Charge Processes

Highly crystalline CuFeS₂ containing earth-abundant and environmentally friendly elements prepared via a high-temperature synthesis exhibits an excellent electrochemical performance as an anode material in sodium-ion batteries. The initial specific capacity of 460 mAh g^-1 increases to 512 mAh g^-1 in the 150th cycle and then decreases to a still very high value of 444 mAh g^-1 at 0.5 A g^-1 in the remaining 550 cycles. Even for a large current density, a pronounced cycling stability is observed. Here, we demonstrate that combining the results of X-ray powder diffraction experiments, pair distribution function analysis, and ²³Na NMR and Mössbauer spectroscopy investigations performed at different stages of discharging and charging processes allows elucidation of very complex reaction mechanisms. In the first step after uptake of 1 Na/CuFeS₂, nanocrystalline NaCuFeS₂ is formed as an intermediate phase, which surprisingly could be recovered during charging. On increasing the Na content, Cu⁺ is reduced to nanocrystalline Cu, while nanocrystalline Na₂S and nanosized elemental Fe are formed in the discharged state. After charging, the main crystalline phase is NaCuFeS₂. At the 150th cycle, the mechanisms clearly changed, and in the charged state, nanocrystalline Cu_xS phases are observed. At later stages of cycling, the mechanisms are altered again: NaF, Cu₂S, and Cu_7.2S₄ appeared in the discharged state, while NaF and Cu₅FeS₄ are observed in the charged state. In contrast to a typical conversion reaction, nanocrystalline phases play the dominant role, which are responsible for the high reversible capacity and long-term stability.

Unraveling the Beneficial Microstructure Evolution in Pyrite for Boosted Lithium Storage Performance

Pyrite FeS₂ as a high-capacity electrode material for lithium-ion batteries (LIBs) is hindered by its unstable cycling performance owing to the large volume change and irreversible phase segregation from coarsening of Fe. Here, the beneficial microstructure evolution in MoS₂ -modified FeS₂ is unraveled during the cycling process; the microstructure evolution is responsible for its significantly boosted lithium storage performance, making it suitable for use as an anode for LIBs. Specifically, the FeS₂ /MoS₂ displays a long cycle life with a capacity retention of 116 % after 600 cycles at 0.5 A g^-1 , which is the best among the reported FeS₂ -based materials so far. A series of electrochemical tests and structural characterizations substantially revealed that the introduced MoS₂ in FeS₂ experiences an irreversible electrochemical reaction and thus the in situ formed metallic Mo could act as the conductive buffer layer to accelerate the dynamics of Li⁺ diffusion and electron transport. More importantly, it can guarantee the highly reversible conversion in lithiated FeS₂ by preventing Fe coarsening. This work provides a fundamental understanding and an effective strategy towards the microstructure evolution for boosting lithium storage performances for other metal sulfide-based materials.

Hydrothermally synthesized chalcopyrite platelets as an electrode material for symmetric supercapacitors

A novel chalcopyrite (CuFeS₂) platelet like open-pored micro-flower nanostructure investigated as an electrode material for supercapacitors.

Exploration and Size Engineering from Natural Chalcopyrite to High-Performance Electrode Materials for Lithium-Ion Batteries

Compared to chemosynthetic CuFeS₂, natural chalcopyrite (CuFeS₂) can be regarded as a promising anode material for exploring ultrafast and stable Li-ion batteries benefiting from it being firsthand, eco-friendly, and resource-rich. Considering the nonuniform size distribution in it and the fact that homogeneous grain distributions can effectively restrain the aggregation of active materials, the engineering of size is deemed an effective strategy to achieve excellent Li-storage performances. Herein, varisized natural CuFeS₂ are obtained by facial mineral processing technology and outstanding Li-storage performances are exhibited. Along with the decreasing of size, the contribution of pseudocapacitive as well as the ion transfer rates are significantly boosted. As expected, even at 1 A g^-1, a remarkable capacity of 1009.7 mA h g^-1 is displayed by the sample with the smallest size and most uniform distributions even after 500 cycles. Furthermore, supported by the detailed analysis of in situ X-ray diffraction and kinetic features, a hybrid of multiple lithium-metal sulfur systems and the major origin of the enhanced capacity upon long cycles are confirmed. Remarkably, this work is expected to increase the far-ranging applications of natural chalcopyrite as a firsthand anode material for lithium-ion batteries (LIBs) and inform the readers about the effects of particle size on Li-storage performances.

Natural chalcopyrite as a sulfur source and its electrochemical performance for lithium–sulfur batteries

Natural chalcopyrite with high capacity and good cycling performance is used as a sulfur source for lithium–sulfur batteries.

CuFe2S3 as electrode material for Li-ion batteries

Electrochemical performances of the isocubanite CuFe₂S₃ tested as electrode material for Li-ion batteries have been investigated. A first discharge capacity of 860 mA h g^-1 shows a conversion process leading to Li₂S, copper and iron nanoparticles. Interestingly, a reversible capacity of 560 mA h g^-1 at 1.5 V is demonstrated with good cyclability up to 30 cycles.