Search Results (40)

The expensive nature and limited availability of platinum (Pt) cathodes pose a significant challenge for the widespread adoption of microbial fuel cell (MFC) technology. Although many alternatives have been studied, very few reports provide a systematic head-to-head comparison of different Ni–oxide cathodes under the same operational conditions. This research investigates cost-effective nickel-based metal oxide composites (Ni–TiO₂, Ni–Cr₂O₃, Ni–Al₂O₃) as catalysts for the oxygen reduction reaction (ORR), using Pt as a reference point. The performance of the MFC was thoroughly evaluated in terms of power output, chemical oxygen demand (COD) removal, and Coulombic efficiency (CE). The Pt cathode exhibited the highest performance (275 mW m⁻², 87% COD removal, 35% CE), confirming its catalytic advantages. Among the alternative materials, the Ni–TiO₂ composite yielded the best outcomes (224 mW m⁻², 79% COD removal, 17.7% CE), markedly surpassing the performances of Ni–Cr₂O₃ (162 mW m⁻², 72%, 24% CE) and Ni–Al₂O₃ (134 mW m⁻², 64%, 11.6% CE). Koutecký–Levich analysis clarified the mechanisms at play: Pt facilitated a direct 4-electron ORR process, while the composites operated through a 2-electron mechanism. Notably, the semiconductor properties of Ni–TiO₂ resulted in a higher electron transfer number (n = 2.8) compared to the other composites (n ≈ 2.3), which accounts for its increased efficiency. With its low production cost, Ni–TiO₂ presents an exceptional cost-to-performance ratio. By linking catalytic performance directly to the electronic nature of the oxide supports, this study offers clear design guidelines for selecting non-precious cathodes. The dual evaluation of electrochemical efficiency and cost-to-performance distinguishes this study from prior reports and underscores its practical significance and originality. This study highlights Ni–TiO₂ as a highly sustainable and economically viable catalyst, making it a strong candidate to replace Pt for practical MFC applications that focus on simultaneous power generation and wastewater treatment. Full article

Magma oxidation state and water content are pivotal factors governing porphyry copper mineralization. The Xiongcun deposit, the only super-large porphyry copper deposit (PCD) formed in an oceanic subduction environment in the Gangdese belt, has been the primary focus of prior research, with limited systematic comparisons conducted among Xiongcun, weakly mineralized, and barren igneous rocks across the Jurassic Arc. Furthermore, the interaction between ore-controlling factors and deep-seated magmatic processes remains poorly understood. This study examines Xiongcun volcanic rocks, as well as weakly mineralized and barren volcanic rocks from the Jurassic Arc, with Dazi and Jiamagou samples from the eastern segment of Jurassia Arc (ESJA) and Xiongcun, Chucun, and Qinze samples from the western segment of Jurassia Arc (WSJA). All samples (168.0–184.8 Ma) are predominantly calc-alkaline, which is typical of arc magmas. Zircon Hf isotopic data reveal pronounced E-W variations but minimal N-S differences, dividing the arc into the WSJA and ESJA subzones. The WSJA volcanic rocks exhibit uniform Hf isotopic signatures (ε_Hf(t) = 11.2–16.3) and young crustal model ages (186–500 Ma), whereas the ESJA mantle source region is heterogeneous, reflecting greater retention of ancient crustal material. Compared to the ESJA, new data from WSJA samples display higher zircon Ce⁴⁺/Ce³⁺ ratios (454 vs. 145), lower T(Zr-Ti) values (716 °C vs. 779 °C), and elevated whole-rock Ba/La ratios. These differences suggest that mineralization contrasts between the two segments arise from varying fluid metasomatism in their source regions, leading to divergent magma oxygen fugacity and water content—critical controls on porphyry Cu formation. The WSJA magmas exhibit higher values in both parameters, while the ESJA lacks significant mineralization potential. Full article

The narrow operating temperature window of commercial V-W/TiO₂ catalysts severely limits NO_x removal efficiency, especially during low-load boiler operations. To achieve broad-temperature NO_x abatement, we developed Ce-M/Ti (M = Co, Fe, Mn, Mo) catalysts via a dual-site strategy. The temperatures required for 80% NO conversion (T₈₀) were 302 °C for Ce-Mo/Ti, 372 °C for Ce-Fe/Ti, 393 °C for Ce-Mn/Ti, and 415 °C for Ce-Co/Ti. Among them, Ce-Mo/Ti exhibited the most favorable low-temperature activity, outperforming a commercial catalyst (324 °C). Its turnover frequency (3.12 × 10⁻³ s⁻¹) was 1.29 times higher. Combined physicochemical characterization and density functional theory (DFT) calculations further reveal the mechanism behind the enhanced dual-site synergy in Ce-Mo/Ti. In the Ce-Co, Ce-Fe, and Ce-Mn sites, weak orbital hybridization leads to limited charge transfer. In contrast, Ce-Mo/Ti exhibits stronger hybridization between the Ce 4f/5d and Mo 4d orbitals, which breaks the inherent limitation of the Ce-based (Ce³⁺/Ce⁴⁺) redox capability and enables reverse electron transfer from Mo to Ce. This distinctive electron transfer direction creates a unique electronic environment, activating an efficient redox cycle between Mo⁶⁺/Mo⁵⁺ and Ce⁴⁺/Ce³⁺. This work offers a promising design strategy for dual-site catalysts with high NO_x removal efficiency over a wide temperature range. Full article

This study aims to develop an AB₂-type Ti-Mn-based alloy with low operating pressure and favorable activation performance for use in a compact hydrogen storage tank. The optimized alloy, Ti_0.75Zr_0.25Cr_0.75Mn_1.2 + 1.5 wt.% Ce, was produced at scale and exhibits a maximum hydrogen storage capacity of 1.87 wt.% and excellent hydrogen activation properties. Furthermore, compositing the mass-produced alloy with 5 wt.% aluminum foam increases the hydride tank’s hydrogen discharge rate by 50%. A prototype aluminum tank containing 57.8 g of hydrogen is demonstrated to stably supply hydrogen to a 220 W fuel cell, enabling continuous operation at rated power output. The work provides a material solution with potential industrial applicability for compact, low-pressure hydrogen storage systems. Full article

In this work, a gradient leaching strategy for stepwise extraction of tungsten and cerium from a spent W-Ce/TiO₂ catalyst has been developed. Results of a thermodynamic analysis indicated that high-temperature alkaline leaching and low-temperature acid leaching were conducive to the extraction of W and Ce, respectively. The effects of leaching agent type, concentration, temperature, and liquid-to-solid ratio on the leaching rates of W and Ce were systematically investigated. Experimental results revealed that the leaching ratio of W reached 90.92% under optimized conditions of 3 mol/L NaOH, 100 °C, 1 h, and a liquid-to-solid ratio of 20:1 for the alkaline leaching in the first stage. The leaching ratio for Ce reached 91.96% under optimized conditions of 1 mol/L H₂SO₄, 50 °C, 2 h, and a liquid-to-solid ratio of 12:1 for acidic leach in the second stage. The leaching ratios of titanium and aluminum were limited to 1.76% and 4.42%, respectively, indicating that >90% of these elements were virtually undissolved during the two-stage leaching process. The final leaching residue after the two-stage leaching contained >91.88 wt% TiO₂. Consequently, this study not only demonstrated effective separation of W, Ce, and Ti, but also provided an innovative solution for the environmentally friendly treatment and resource utilization for spent W-Ce/TiO₂ catalysts. Full article

Chelidonium majus L. is a species with a wide medicinal use, commonly found in anthropogenically degraded habitats, forest edges, and urban parks. This study aimed to determine the chemical composition of the leaves, stems, and roots of Ch. majus and the soil in its rhizosphere in terms of the content of the main elements (Fe, Ca, P, Mg, Al, Na, K, S), trace elements and rare earth minerals (Ti, Mo, Ag, U, Au, Th, Sb, Bi, V, La, B, W, Sc, Tl, Se, Te, Ga, Cs, Ge, Hf, Nb, Rb, Sn, Ta, Zr, Y, Ce, In, Be, and Li), and their comparison in the parts analyzed. The study was conducted in five urban parks in southern Poland in a historically industrialized area. The results showed that Ca has the highest content among the macroelements. Its leaf content ranges from 24,700 to 40,700 mg·kg⁻¹, while in soil, it ranges from 6500 to 15,000 mg·kg⁻¹. In leaves, low values of Al (100–500 mg·kg⁻¹) and Na (100 mg·kg⁻¹) were found in comparison to the other elements tested, while high values of Al (5100–9800 mg·kg⁻¹) were found in soils. Among the macroelements in the Ch. majus stems, K showed the highest concentration (>100,000 mg·kg⁻¹), while the Ca content was 3–4 times lower in the stems than in the leaves. Rhizomes of Ch. majus accumulate the most K and Ca, in the range of 22,800–29,900 mg·kg⁻¹ and 5400–8900 mg·kg⁻¹, respectively. Fe and Al in all locations have higher values in the soil than in the tissues. In turn, the content of Ca, P, Mg, K, and S is higher in plants than in the soil. Determining the elemental content of medicinal plants is important information, as the plant draws these elements from the soil, and, at higher levels of toxicity, it may indicate that the plant should not be taken from this habitat for medicinal purposes. Full article

In this work, a novel potential thermal barrier coating material entropy-stabilized titanium–aluminum oxide (La_0.25Ce_0.25Nd_0.25Sm_0.25)Ti₂Al₉O₁₉ (META) was successfully synthesized by the solid-state reaction method, and its thermophysical properties, phase stability, infrared emissivity, mechanical properties, and CMAS corrosion resistance were systematically investigated. The results demonstrated that META exhibits low thermal conductivity at 1100 °C (1.84 W·(m·K)⁻¹), with a thermal expansion coefficient (10.50 × 10⁻⁶ K⁻¹, 1000–1100 °C) comparable to yttria-stabilized zirconia (YSZ). Furthermore, META displayed desirable thermal stability, high emissivity within the wavelength range of 2.5–10 μm, and improved mechanical properties. Finally, META offers superior corrosion resistance due to its excellent infiltration inhibiting. The bi-layer structure on the corrosion surface prevents the penetration of the molten CMAS. Additionally, doping small-radius rare-earth elements thermodynamically stabilizes the reaction layer. The results of this study indicate that (La_0.25Ce_0.25Nd_0.25Sm_0.25)Ti₂Al₉O₁₉ has the potential to be a promising candidate for thermal barrier coating materials. Full article

Bi₂O₂Se, as the n-type counterpart of p-type BiCuSeO, has garnered considerable attention. The lower carrier concentration leads to reduced electrical conductivity, prompting extensive research efforts aimed at enhancing its electrical performance. This study prepared Bi_2−3x(CeTiSn)_xO₂Se (x = 0, 0.02, 0.03, and 0.04) ceramics using a combination of high-energy ball milling and cold isostatic pressing techniques. Results demonstrated that the incorporation of multiple elements led to an increase in the carrier concentration within the Bi₂O₂Se system, thereby improving electrical conductivity. The electrical conductivity increased from 5.1 S/cm for Bi₂O₂Se to 154.1 S/cm for Bi_1.88(CeTiSn)_0.04O₂Se at 323 K. Furthermore, the maximum power factor value of Bi_1.88(CeTiSn)_0.04O₂Se was 112 μW m⁻¹ K⁻² at 763 K. Doping led to a slight increase in thermal conductivity. The figure of merit ZT_max value of Bi_1.88(CeTiSn)_0.04O₂Se was ~0.16, marking a significant enhancement of about 1.45 times compared to that of the pure sample (~0.11). Full article

Electrochromic capacitors, which are capable of altering their appearances in line with their charged states, are drawing substantial attention from both academia and industry. Tungsten oxide is usually used as an electrochromic layer material for electrochromic devices, or as an active material for high-performance capacitor electrodes. Despite this, acceptable visual aesthetics in electrochromic capacitors have almost never been achieved using tungsten oxide, because, in its pure form, this compound only displays a onefold color modulation from transparent to blue. Herein, we have designed W/WO₃/TiO₂ multilayer films by a magnetron sputtering device. The impact of TiO₂ layer on the optical and electrochemical properties was investigated. The results show that the optimum thickness of the TiO₂ layer is 10 nm. The as-prepared film displays a high coloration efficiency (CE) of 74.2 cm² C⁻¹, a high areal capacitance of 32.0 mF/cm², an excellent rate performance (with the areal capacitance still retaining 87% of the maximum capacitance at a current density of 1 mA/cm²), and a high cycle life (with a capacity retention of 91% after 1000 cycles). Full article

Nitrogen oxides (NO_x) and chlorobenzene (CB) released during waste incineration and iron ore sintering pose significant threats to both the atmosphere and human health, necessitating effective control measures. Vanadium-based catalysts are commonly employed for the simultaneous control of NO_x and CB; however, their catalytic performance requires further enhancement. In this study, the NH₃-SCR activity and CB catalytic oxidation (CBCO) activity were significantly enhanced by doping the V10W/Ti catalyst with Ce. During the multi-pollutant control (MPC) reaction, the optimized 15CeV10W/Ti catalyst demonstrated NO_x conversion approaching 100% and N₂ selectivity exceeding 95% at temperatures between 210 and 450 °C. Additionally, it achieved CB conversion nearing 100% and CO₂ selectivity above 80% at temperatures above 350 °C. These results were markedly superior to those of the conventional commercial 1%V₂O₅–10%WO₃/TiO₂ catalyst. Characterization studies indicated that the 15CeV10W/Ti catalyst possessed improved redox performance and more acidic sites. In the MPC reaction, the declined CBCO activity, compared to the CB separate oxidation, can be attributed primarily to the competitive adsorption of NH₃ with CB. Conversely, the observed decrease in NO_x conversion at lower temperatures was primarily due to the suppression of the oxidation of NO to NO₂ by CB. Full article

Ce-based catalysts have been widely used in the removal of nitrogen oxides from industrial flue gas because of their good catalytic performance and environmental friendliness. However, the mechanism of alkali metal poisoning in Ce-based catalysts remains to be further studied. This work involves the preparation of the K/Na-poisoned CeWTi catalyst via the impregnation method for assessing its performance in NO removal. Experiments show that both K and Na exhibit detrimental effects on the CeWTi catalyst, and the loading of alkali metal reduces the specific surface area and pore volume of the catalyst. Furthermore, the presence of alkaline metals results in a notable decline in the CeWTi acid concentration, particularly in Lewis acid sites. Concurrently, the levels of Ce³⁺, oxygen vacancies, and reducing agents on the catalyst surface decrease, leading to diminished reduction capability and eventual catalyst deactivation. The application of a BP neural network for catalyst activity prediction yielded an average relative error of approximately 0.73%, indicating enhanced accuracy in prediction outcomes. This work explored the cause of alkali metal poisoning of the CeWTi catalyst and provided an effective prediction method for the lifetime of CeWTi catalyst, which provided theoretical guidance for the engineering application of Ce-based catalysts. Full article

A novel TiB₂-CeO₂-modified (Nb,Mo,Cr,W)Si₂ coating was prepared on a Nb-5W-2Mo-1Zr alloy substrate using two-step slurry sintering and halide-activated pack cementation to address the limitations of a single NbSi₂ coating in meeting the service requirements of niobium alloys at elevated temperatures. At 1700 °C, the static oxidation life of the coating exceeded 20 h, thus indicating excellent high-temperature oxidation resistance. This was due to the formation of a TiO₂-SiO₂-Cr₂O₃ composite oxide film on the coating surface, which, due to low oxygen permeability, effectively prevented the inward infiltration of oxygen. Additionally, the dense structure of the composite coating further enhanced this protective effect. The composite coating was able to withstand over 1600 thermal shock cycles from room temperature to 1700 °C, and its excellent thermal shock performance could be attributed to the formation of MoSi₂, CrSi₂, and WSi₂ from elements such as Mo, Cr, and W, which were added during modification. In addition to adjusting the difference in thermal expansion coefficients between the layers of composite coatings to reduce the thermal stress generated by thermal shock cycles, the formation of silicide compounds also improved the overall fracture toughness of the coating and thereby improved its thermal shock resistance. Full article

This study aims to investigate the depositional environment, sediment sources, and elemental occurrence of Upper Paleozoic coal in the Renjiazhuang Mining District, Western Ordos Basin. Furthermore, SEM-EDX, optical microscope (OM), ICP-AES, ICP-MS, and AAS were used. Compared with hard coal of the world, M3 coals were enriched in Ga, Li, Zr, Be, Ta, Hf, Nb, Pb, and Th, M5 coals were enriched in Li (CC = 10.21), Ta (CC = 6.96), Nb (CC = 6.95), Be, Sc, Ga, Hf, Th, Pb, Zr, In, and REY, while M9 coals were enriched in Li (CC = 14.79), Ta (CC = 5.41), Ga, W, Hf, Nb, Zr, Pb, and Th. In addition, minerals were mainly composed of kaolinite, dolomite, pyrite, feldspar, calcite, and quartz, locally visible minor amounts of monazite, zircon, clausthalite, chalcopyrite, iron dolomite, albite, fluorite, siderite, galena, barite, boehmite, and rutile. In addition, maceral compositions of M3 coals and M9 coals were dominated by vitrinite (up to 78.50%), while M5 coals were the main inertite (up to 76.26%), and minor amounts of liptinite. REY distribution patterns of all samples exhibited light REY enrichment and negative Eu anomalies. The geochemistry of samples (TiO₂ and Al₂O₃, Nb/Y and Zr × 0.0001/TiO₂ ratios, and REY enrichment types) indicates that the sediment sources of samples originated from felsic igneous rocks. Indicator parameters (TPI, GI, VI, GWI, V/I, Sr/Ba, Th/U, and Ce_N/Ce_N*) suggest that these coals were formed in different paleopeat swamp environments: M3 coal was formed in a lower delta plain and terrestrial (lacustrine) facies with weak oxidation and reduction, and M5 coal was formed in a terrestrial and dry forest swamp environment with weak oxidation–oxidation, while M9 coal was formed in a seawater environment of humid forest swamps and the transition from the lower delta plain to continental sedimentation with weak oxidation and reduction. Statistical methods were used to study the elemental occurrence. Moreover, Li, Ta, Hf, Nb, Zr, Pb, and Th elements were associated with aluminosilicates, and Ga occurred as silicate. Full article

The assessment of soil contamination in the vicinity of integrated siderurgical plants is of outmost importance for agroecosystems and human health, and sensitive techniques should be employed for accurate assessment of chemical elements (metals, potential toxic elements, rare earths, radioelements) in soil and further evaluation of potential ecological and safety risk. In this paper a total of 45 major, minor and trace elements (Al, As, Au, Ba, Br, Ca, Cd, Ce, Co, Cr, Cs, Cu, Dy, Eu, Fe, Hf, Hg, I, K, La, Mg, Mn, Mo, Na, Nd, Ni, Pb, Rb, Sb, Sc, Sm, Sn, Sr, Ta, Tb, Th, Ti, Tm, U, V, W, Y, Yb, Zn and Zr) were quantified in soils located around a large siderurgical works (Galati, SE Romania) using instrumental neutron activation analysis (INAA) in combination with X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP–MS). The statistical analysis results and vertical distribution patterns for three depths (0–5 cm, 5–20 cm, 20–30 cm) indicate inputs of toxic elements in the sites close to the ironmaking and steelmaking facilities and industrial wastes dumping site. For selected elements, a comparison with historical, legislated and world reported concentration values in soil was performed and depth migration, contamination and toxic risk indices were assessed. The distribution of major, rock forming elements was closer to the Upper Continental Crust (UCC), and to the Dobrogea loess, a finding confirmed by the ternary diagram of the incompatible trace elements Sc, La and Th, as well as by the La to Th rate. At the same time, the La/Th vs. Sc and Th/Sc vs. Zr/Sc bi-plots suggested a felsic origin and a weak recycling of soils’ mineral components. Full article

Marine Co-rich ferromanganese crusts and polymetallic nodules, which are widely distributed in oceanic environments, are salient potential mineral resources that are enriched with many critical metals. Many investigations have achieved essential progress and findings regarding critical metal enrichment in Fe-Mn crusts and nodules. This study systematically reviews the research findings of previous investigations and elaborates in detail on the enrichment characteristics, enrichment processes and mechanisms and the influencing factors of the critical metals enriched in Fe-Mn crusts and nodules. The influencing factors of critical metal enrichments in Fe-Mn crusts and nodules mainly include the growth rate, water depth, post-depositional phosphatization and structural uptake of adsorbents. The major enrichment pathways of critical metals in marine Fe-Mn (oxy)hydroxides are primarily as follows: direct substitution on the surface of δ-MnO₂ for Ni, Cu, Zn and Li; oxidative substitution on the δ-MnO₂ surface for Co, Ce and Tl; partition between Mn and Fe phases through surface complexation according to electro-species attractiveness for REY (except for Ce), Cd, Mo, W and V; combined Mn-Fe phases enrichment for seawater anionic Te, Pt, As and Sb, whose low-valence species are mostly oxidatively enriched on δ-MnO₂, in addition to electro-chemical adsorption onto FeOOH, while high-valence species are likely structurally incorporated by amorphous FeOOH; and dominant sorption and incorporation by amorphous FeOOH for Ti and Se. The coordination preferences of critical metals in the layered and tunneled Mn oxides are primarily as follows: metal incorporations in the layer/tunnel-wall for Co, Ni and Cu; triple-corner-sharing configurations above the structural vacancy for Co, Ni, Cu, Zn and Tl; double-corner-sharing configurations for As, Sb, Mo, W, V and Te; edge-sharing configurations at the layer rims for corner-sharing metals when they are less competitive in taking up the corner-sharing position or under less oxidizing conditions when the metals are less feasible for reactions with layer vacancy; and hydrated interlayer or tunnel-center sorption for Ni, Cu, Zn, Cd, Tl and Li. The major ore-forming elements (e.g., Co, Ni, Cu and Zn), rare earth elements and yttrium, platinum-group elements, dispersed elements (e.g., Te, Tl, Se and Cd) and other enriched critical metals (e.g., Li, Ti and Mo) in polymetallic nodules and Co-rich Fe-Mn crusts of different geneses have unique and varied enrichment characteristics, metal occurrence states, enrichment processes and enrichment mechanisms. This review helps to deepen the understanding of the geochemical behaviors of critical metals in oceanic environments, and it also bears significance for understanding the extreme enrichment and mineralization of deep-sea critical metals. Full article