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In this study, a CuO modified the MnO.sub.2 nano-hollow spheres sorbent was prepared using the impregnation method. The effects of the CuO loading amount, reaction temperature, gas hourly space velocity, and flue gas component on the Hg.sup.0 removal performance of the sorbent were investigated. When loaded with 10% CuO, the sorbent's Hg.sup.0 removal efficiency was higher than 95% from 150 to 250 °C. The combination of plentiful acid sites and superior redox behavior ensured the efficient adsorption and oxidation of Hg.sup.0, which endowed the 10% CuO-doped sorbent with a satisfactory Hg.sup.0 removal performance over a wide temperature range. Throughout the Hg.sup.0 capture cycles, the Mars-Maessen mechanism well-depicted the Hg.sup.0 removal process over the 10% Cu/Mn adsorbent, the Mn.sup.4+, Cu.sup.2+, and chemisorbed oxygen acted as the active sites with HgO being the end product. However, the weak flue gas component adaptability demonstrated that further modification is needed to enhance the practicality of this system.

Cuprous oxide (Cu.sub.2O) nano- and microstructures possess unique properties that may find a variety of applications. Environmentally benign synthesis of Cu.sub.2O with well-controlled morphology is highly desirable. In this study, Cu.sub.2O crystals with tunable shapes are synthesized using cellulose nanofibrils (CNFs) as a shape regulator and the sole reducing agent in aqueous environment. By simply increasing Cu.sub.2O precursor concentration, the Cu.sub.2O crystals evolved from octahedra to cuboctahedra, and finally cubes, accompanied with increasing size from nano- to microscale. The selection of Cu chelating agent (sodium tartrate or potassium sodium tartrate) affected the crystal growth rate. Transition in the relative intensities of the (111) and the (200) crystalline peaks in their XRD patterns was consistent with the morphology change. During the growth of crystals, CNFs were preferably bound to the 111 crystalline facet. The introduction of KBr to the reaction system produced short hexapods. The resultant CNF-Cu.sub.2O hybrids were incorporated into waterborne polyurethane (WPU) films. Even with 0.5 wt% CNF-Cu.sub.2O, the WPU film showed significant enhancement in modulus, strength and elongation at break. This work proves the possibility of controlled growth of Cu.sub.2O particles aided by CNFs and provides a new strategy for improving the performance of eco-friendly WPU films.

Copper selenide (Cu[sub.2]Se) has garnered significant attention as an exceptional thermoelectric material due to its high thermoelectric figure of merit (ZT values > 2). This remarkable efficiency makes it a strong candidate for various applications. However, the practical deployment of thermoelectrics often requires operation in an oxygen-containing atmosphere, which poses a significant challenge for Cu[sub.2]Se due to its environmental instability. This work investigates the environmental behavior of high-purity Cu[sub.2]Se, which was synthesized via a direct high-temperature reaction and spark plasma sintering (SPS). Our Temperature-Programmed Oxidation (TPO) studies determined that the onset of oxidation occurs at a temperature as low as 623 K. Further analysis using SEM–EDS confirmed the formation of copper oxides, Cu[sub.2]O and CuO. Critically, thermogravimetric analysis (TGA) revealed that the SeO[sub.2] formation and sublimation process is an equally profound degradation mechanism, alongside copper oxidation, particularly within the optimal 673–973 K temperature range. Complementary XRD studies of samples annealed in air underscore this severe material degradation, which is especially devastating between 873 and 973 K. Ironically, this is the precise temperature window where Cu[sub.2]Se’s highest ZT values have been reported. Our findings demonstrate that the direct application of Cu[sub.2]Se in air is impractical, highlighting the urgent need for developing robust protective layers to unlock its full potential.

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In this work, we studied Cu-doped and (Cu,Y)-codoped ZrO[sub.2] nanopowders produced through a coprecipitation approach to identify the nature of Cu-related bulk and surface paramagnetic centers. We conducted EPR, NMR, and Raman scattering studies on Cu- and (Cu,Y)-doped ZrO[sub.2] powders calcined at different temperatures. At low calcination temperatures (400 °C) and low Cu loading (0.1–1.0 mol.% of CuO), the EPR signal was found to be attributed to surface-related Cu-H[sub.2]O complexes. For powders with higher Cu content (up to 8.0 mol.% of CuO), the superparamagnetic signal associated with the formation of copper clusters was observed. At higher calcination temperatures, the destruction of Cu-related surface complexes promotes the incorporation of Cu[sup.2+] ions into the bulk of ZrO[sub.2] nanocrystals at Zr positions. Co-doping ZrO[sub.2] with Cu and Y was observed to facilitate the incorporation of Cu[sup.2+] ions into cation sites at lower calcination temperatures when compared with Cu-doped ZrO[sub.2].

As a candidate for photocatalyst, the photocatalytic performance of cuprous oxide (Cu.sub.2O) is severely restricted by its high charge carrier recombination rate, self-photocorrosion and the uncertainty of crystal plane. In order to improve the photocatalytic performance and deeply analyze the photocatalytic mechanism, the Cu.sub.2O nanocrystals with cubic, cuboctahedral and octahedral structures were combined with n-type ZnO to prepare Cu.sub.2O/ZnO heterojunction photocatalysts. The effects of crystal facet of Cu.sub.2O and Zn/Cu ratios on the photocatalytic performances of Cu.sub.2O/ZnO heterojunctions were explored into. The results show that the cuboctahedron Cu.sub.2O with 100 and 111 facets exhibits more surprising catalytic performance due to the energy-level difference between the two facets, leading to higher electron-hole pair separation efficiency when compared with the octahedral Cu.sub.2O with 111 facets and cubic Cu.sub.2O with 100 facets. In addition, optimized Cu.sub.2O/ZnO heterojunction with appropriate Zn/Cu ratio exhibits the collaborative advantages of the two materials, so the catalytic activity and stability are effectively improved.

The reaction of ethanol with surface OH groups on ZrO[sub.2], CuO/ZrO[sub.2], CuO, Al[sub.2]O[sub.3], Ga[sub.2]O[sub.3], NiO, and SiO[sub.2] was studied by IR spectroscopy. The basicity of oxides was followed by CO[sub.2] adsorption, and their ability to oxidize was investigated by H[sub.2]-TPR. It has been found that ethanol reacts with surface OH groups forming ethoxy groups and water. Some oxides: ZrO[sub.2], CuO/ZrO[sub.2], Al[sub.2]O[sub.3], and Ga[sub.2]O[sub.3] contain several kinds of OH groups (terminal, bidentate, and tridentate) and terminal hydroxyls react with ethanol in the first order. Two kinds of ethoxyls are formed on these oxides: monodental and bidental ones. On the other hand, only one kind of ethoxy group is formed on CuO and NiO. The amount of ethoxy groups correlates with the basicity of oxides. The biggest amount of ethoxyls is produced on the most basic: ZrO[sub.2], CuO/ZrO[sub.2], and Al[sub.2]O[sub.3], whereas the smallest amount of ethoxyls is produced on CuO, NiO, and Ga[sub.2]O[sub.3], i.e., on oxides of lower basicity. SiO[sub.2] does not form ethoxy groups. Above 370 K ethoxy groups on CuO/ZrO[sub.2], CuO, and NiO are oxidized to acetate ions. The ability of oxides to oxidize ethoxyl groups increases in the order NiO < CuO < CuO/ZrO[sub.2]. The temperature of the peak in the H[sub.2]-TPR diagram decreases in the same order.

This report analyses the effect of tungsten diselenide (WSe.sub.2) and PEDOT:PSS, as a hole transport layer (HTL) in copper oxide (CuO) and tin disulphide (SnS.sub.2) heterojunction based photodetector. The device having PEDOT:PSS hole transport layer offers a broad spectrum detection covering ultra-violet (300-400 nm), visible (400-800 nm), and near-infrared region (up to 1250 nm). On application of WSe.sub.2 as HTL, performance parameters of the photodetector are improved significantly. For the Al/SnS.sub.2/CuO/WSe.sub.2/ITO on PET device at 0.118 µW incident power (at 600 nm) and -1 V reverse bias, responsivity, external quantum efficiency, detectivity, and sensitivity are 81.34 A/W, 16812.11%, 1.47 x 10.sup.12 J, and 12.72, respectively. For Al/SnS.sub.2/CuO/PEDOT:PSS/ITO/PET device these values are 11.373 A/W, 1128.27%, 2.52 x 10.sup.11 J, and 2.69 at 1250 nm wavelength. The performance parameters obtained for device with WSe.sub.2 HTL prove its effectiveness as HTL.

Pure tin oxide (SnO[sub.2]) as a typical conductometric hydrogen sulfide (H[sub.2]S) gas-sensing material always suffers from limited sensitivity, elevated operation temperature, and poor selectivity. To overcome these hindrances, in this work, hollow CuO-SnO[sub.2] nanotubes were successfully electrospun for room-temperature (25 °C) trace H[sub.2]S detection under blue light activation. Among all SnO[sub.2]-based candidates, a pure SnO[sub.2] sensor showed no signal, even toward 10 ppm, while the 1% CuO-SnO[sub.2] sensor achieved a limit of detection (LoD) value of 2.5 ppm, a large response of 4.7, and a short response/recovery time of 21/61 s toward 10 ppm H[sub.2]S, as well as nice repeatability, long-term stability, and selectivity. This excellent performance could be ascribed to the one-dimensional (1D) hollow nanostructure, abundant p-n heterojunctions, and the photoelectric effect of the CuO-SnO[sub.2] nanotubes. The proposed design strategies cater to the demanding requirements of high sensitivity and low power consumption in future application scenarios such as Internet of Things and smart optoelectronic systems.

7,7,8,8-Tetracyanoquinomethane (TCNQ) was added to polyvinylpyrrolidone (PVP)/CuO composites to modify and prevent agglomeration of the particles, and thus the CuO particles were well dispersed to a small size, thereby increasing CO[sub.2] solubility and separation performance. When the separation performance of the PVP/CuO/TCNQ composite membrane was measured for CO[sub.2]/N[sub.2] gases, a CO[sub.2] separation of about 174 was measured. This improvement in performance was attributed to the fact that TCNQ was applied to PVP and CuO to prevent agglomeration between particles with surface modification. Due to TCNQ, CuO could be dispersed to a small size in PVP; the bonds between chains in PVP weakened; the interaction between molecules weakened; and the free volume increased, as confirmed by FT-IR, TGA, and UV–Vis spectroscopy.