All-solid-state Z-Scheme photocatalysts have attracted significant attention due to their great potential for solar fuel production. However, delicately coupling two individual semiconductors with a charge shuttle by a material strategy remains a challenge. Herein, we demonstrate a new protocol of natural Z-Scheme heterostructures by strategically engineering the component and interfacial structure of red mud bauxite waste. Advanced characterizations elucidated that the hydrogen-induced formation of metallic Fe enabled the effective Z-Scheme electron transfer from γ-Fe 2 O 3 to TiO 2 , leading to the significantly boosted spatial separation of photo-generated carriers for overall water splitting. To the best of our knowledge, it is the first Z-Scheme heterojunction based on natural minerals for solar fuel production. Thus our work provides a new avenue toward the utilization of natural minerals for advanced catalysis applications.
Two-dimensional nanomaterials hold great promise as electrode materials for the construction of excellent electrochemical energy storage and transformation apparatuses. In the study, metallic layered cobalt sulfide was, firstly, applied to the area of energy storage as a supercapacitor electrode. By a facile and scalable method for cathodic electrochemical exfoliation, metallic layered cobalt sulfide bulk can be exfoliated into high-quality and few-layered nanosheets with size distributions in the micrometer scale range and thickness in the order of several nanometers. With a two-dimensional thin sheet structure of metallic cobalt sulfide nanosheets, not only was a larger active surface area created, but also, the insertion/extraction of ions in the procedure of charge and discharge were enhanced. The exfoliated cobalt sulfide was applied as a supercapacitor electrode with obvious improvement compared with the original sample, and the specific capacitance increased from 307 F∙g−1 to 450 F∙g−1 at the current density of 1 A∙g−1. The capacitance retention rate of exfoliated cobalt sulfide enlarged to 84.7% from the original 81.9% of unexfoliated samples while the current density multiplied by 5 times. Moreover, a button-type asymmetric supercapacitor assembled using exfoliated cobalt sulfide as the positive electrode exhibits a maximum specific energy of 9.4 Wh∙kg−1 at the specific power of 1520 W∙kg−1.
Mining and smelting effluent have resulted in heavy metal-contaminated groundwater. Copper-polluted groundwater poses a severe threat to human health and the ecological environment. Permeable reactive barrier (PRB) has been rapidly developed as the in situ remediation technology to control toxic copper migration. Low cost, seepage stability, and great longevity are considered within PRB reactive media. In this paper, hydroxyapatite derived from bovine bone was proven to be a suitable adsorbent owing to cost-effectiveness, great adsorption capacity, and longevity. Batch experiments were carried out to determine the copper adsorption behavior as a function of copper concentration and contact time. Adsorption isotherm was represented by the Langmuir isotherm model, and the adsorption capacity of 25.7 mg/g was superior to most of the adsorbents. A kinetic study was accurately fitted by the pseudo-second-order kinetic model interpreted as a chemical reaction. In addition, the column study confirmed hydroxyapatite has excellent hydraulic performance with no clogging phenomenon happened. At C/C0 = 0.5, the number of pore volume (PV) reached 450. The batch and column experiments also revealed that the overall adsorption process followed up the monolayer chemisorption. Furthermore, systematic analyses demonstrated that surface adsorption was responsible for the copper removal by hydroxyapatite based on experimental analysis and density functional theory (DFT) calculations. This work provides an alternative strategy as filling material for in situ remediation of copper-contaminated groundwater and enriches relevant theoretical references.
In this work, a method for controllable regulation of crystal form was proposed for the first time and the effects of different crystal forms on the up-conversion luminescence properties of Ho 3+ , Yb 3+ co-doped K 3 Sc 0.5 Lu 0.5 F 6 (KSLF) phosphors was explored. KSLF:Ho 3+ , Yb 3+ phosphors were synthesized by the high temperature solid-state reaction method, and X-ray diffraction (XRD) results illustrate that the compounds can obtain monoclinic phase and cubic phase at different synthesis temperatures. In addition, according to the powerdependent up-conversion luminescence (UCL) intensity, the UCL mechanism and the electronic transition process are discussed. Simultaneously, the temperature sensing behavior of the best samples with different crystal forms at different temperatures was studied by fluorescence intensity ratio technique. All the results show that KSLF:Ho 3+ , Yb 3+ phosphors show great application potential in the field of temperature sensing, and the preparation of KSLF:Ho 3+ , Yb 3+ in different crystal forms can provide a reference value for crystal design and growth.
The structure type and water content of opal will affect its stability and value.
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