CuO2 Layers Research Articles

InGaN/Cu2O Heterostructure Core-Shell Nanowire Photoanode for Efficient Solar Water Splitting

The heterostructuring and doping concepts have proved to obtain a novel n-InGaN/p-Cu2O nanowire (NW) photoanode by strong enhancement of the photocurrent compared to a bare InGaN NW photoanode in solar water splitting. The large photocurrent is due to the maximized photocarrier separation and hole transfer to the surface in the depletion zone of the p–n heterojunction established by the p-Cu2O layer, forming a thin, uniform shell-layer around the n-InGaN NW core by electrodeposition. For sufficiently thin Cu2O layers, the upward energy band bending in the depletion zone extends up to the surface for optimized hole transport and surface reaction. Thick Cu2O layers on top of the InGaN NWs act as common photocathodes. The functional InGaN/Cu2O heterostructure core-shell NW photoanode is chemically self-stabilized at positive applied voltage by a thin CuO surface layer. Final deposition of the earth-abundant NiOOH co-catalyst boosts the photocurrent of the InGaN/Cu2O/NiOOH complete NW photoanode into the competitive mA/cm2 range.

Improving the Photovoltaic Performance of Flexible Solar Cells with Semitransparent Inorganic Perovskite Active Layers by Interface Engineering.

Inorganic perovskite CsPbBr3 has broad application prospects in photovoltaic windows, tandem cells, and other fields due to its intrinsic semitransparency, excellent photoelectric properties, and stability. In this work, a high-quality semitransparent CsPbBr3 film was prepared by a sequential vacuum evaporation deposition method without high-temperature annealing and successfully used as the active layer of flexible perovskite solar cells (F-PSCs) for the first time, achieving a power conversion efficiency (PCE) of 5.00%. By introducing an energy-level buffer layer of Cu2O between CsPbBr3 and Spiro-OMeTAD, the champion PCE has been further improved to 5.67% owing to the reduction of electron-hole recombination and enhanced charge extraction. The optimized devices present higher stability, which can maintain more than 95% of the initial efficiency even after continuous heating at 85 °C for 240 h. Moreover, the F-PSCs also exhibit excellent mechanical durability, and 90% of the original PCE can be retained after 1000 bending cycles at a curvature radius of 3 mm.

Electrodeposition of cuprous oxide on a porous copper framework for an improved photoelectrochemical performance

Photoelectrochemical (PEC) water splitting can be an efficient and economically feasible alternative for hydrogen production if easily processed photoelectrodes made of inexpensive and abundant materials are employed. Here, we present the preparation of porous Cu2O photocathodes with good PEC performance using solely inexpensive electrodeposition methods. Firstly, porous Cu structures with delicate pore networks were deposited on flat Cu substrates employing hydrogen-bubble-assisted Cu deposition. In a second electrodeposition step, the porous Cu structures were mechanically reinforced and subsequently detached from the substrates to obtain free-standing porous frameworks. In a third and final step, photoactive Cu2O films were electrodeposited. The PEC water splitting performance in 0.5 M Na2SO4 (pH ∼6) shows that these photocathodes have photocurrents of up to −2.25 mA cm−2 at 0 V versus RHE while maintaining a low dark current. In contrast, the Cu2O deposited on a flat Cu sample showed photocurrents only up to −1.25 mA cm−2. This performance increase results from the significantly higher reactive surface area while maintaining a thin and homogeneous Cu2O layer with small grain sizes and therefore higher hole concentrations as determined by Mott-Schottky analysis. The free-standing porous Cu2O samples show a direct optical transmittance of 23% (λ = 400–800 nm) and can therefore be used in tandem structures with a photoanode in full PEC cells.Graphical abstract

Controlled drug release and efficient COD removal using copper immobilized zeolite 4A nanocomposite

The copper oxide –zeolite 4A nanocomposite was prepared by co-precipitation method. XRD analysis confirmed the formation of monoclinic structured CuO nanoparticles having an average diameter of 18 nm on the zeolite surface. FESEM and EDX studies confirmed the formation of CuO NPs in the zeolite framework and 5.6% of copper has been exchanged into the zeolite matrix. The presence of Cu–O bonds in the CuZ nanocomposite (CuZ NC) was also proved by FTIR studies. BET analysis showed that the as-prepared nanocomposite exhibited type IV isotherm adsorption behaviour, which is characteristic of multi-porous materials. The surface area was calculated to be 17.5 m 2 /g indicating the existence of, CuO layer on the zeolite surface and inside the channels. The adsorption studies of sewage using CuZ showed removal efficiency of 97% and 93% for COD and BOD with an adsorbent dosage of 100mg/50 ml of pH 7 for 100 min at 25 °C with an agitation speed of 300 rpm. Equilibrium studies showed that the adsorption mechanism follows the Freundlich model indicating multilayer adsorption. Kinetic data fit well with the pseudo-first-order model which shows that physisorption is favoured than chemisorption . Thermodynamic studies indicated the spontaneous and endothermic behaviour of the process. The drug loading studies showed that CuZ has high loading capacity, low cytotoxicity and slow-release performance for Doxorubicin . CuZ nanocomposite exhibited antagonistic effect on the growth of Bacillus subtilis (B29) and Escherichia coli (E266) bacterial strains with greater inhibition zones . • CuZ NC was synthesised and characterised by XRD, SEM, EDX, BET, and FTIR. • CuZ NC is cytotoxic and a good drug loader for Doxorubicin used in cancer therapy. • Sewage treatment using CuZ NC showed removal efficiency of 97 & 93% for COD and BOD. • CuZ NC showed hostile effect on the growth of E. coli & B. subtilis with high inhibition zones.

Mixed ionic-electronic conductivity, phase stability and electrochemical activity of Gd-substituted La2NiO4+δ as oxygen electrode material for solid oxide fuel/electrolysis cells

Ruddlesden-Popper La2-xGdxNiO4+δ (x = 0–0.4) nickelates were synthesized by glycerol-nitrate combustion technique and explored as potential oxygen electrode materials for solid oxide fuel/electrolysis cells. Similar to the parent La2NiO4+δ, the metastability of RP-type n = 1 structure limits the applicability of La2-xGdxNiO4+δ to temperatures below 900 °C. These solid solutions are mixed conductors with predominantly p-type electronic conductivity that exceeds 50 S/cm at 500–800 °C in air. Substitution by gadolinium does not change the overstoichiometric oxygen content in air but has a negative impact on the mobility of interstitial oxygen, most likely, due to steric effects associated with the lattice shrinkage on doping. The electrochemical activity of bilayer electrodes comprising functional La2-xGdxNiO4+δ and current collecting LaNi0.6Fe0.4O3-δ + 3 wt% CuO layers in contact with Ce0.8Gd0.2O1.9 electrolyte was studied in air at 550–850 °C. Analysis of electrochemical impedance spectroscopy data employing the ALS (Adler-Lane-Steele) model revealed the limiting role of oxygen-ionic conductivity of functional La2-xGdxNiO4+δ materials in overall electrode performance.

Comparison of mechanical and tribological properties of CrBN coatings modified by Ni or Cu incorporation

To compare the merits of Ni and Cu, the mechanical and tribological properties of CrBN coatings modified by Ni or Cu incorporation were studied. The results demonstrated that the CrBN-Cu coatings presented a lower friction coefficient than CrBN and CrBN-Ni coatings owing to the improved lubrication effect of the CuO layer originating from the tribochemical reaction. However, the hardness decline due to Cu incorporation was much greater than that of Ni incorporation. Thus, the CrBN-Cu coatings exhibited a higher wear rate than the CrBN coating. In contrast, the plastic deformation enhancement induced by Ni incorporation exceeded the hardness decline. Therefore, the wear of CrBN-Ni coatings partially turned to plastic deformation to present a lower wear rate than that of the CrBN coating.

Surface Modification of ZnO Nanowires with CuO: A Tool to Realize Highly-Sensitive H2S Sensor

Hydrothermally grown ZnO nanowires (NWs) have been successfully synthesized and surface modified by an ultrathin layer of CuO using dip coating technique to achieve a highly sensitive H2S sensor. XRD analysis confirmed the hexagonal structure of ZnO without any Cu sub-oxide peaks. After CuO modification, the peak shift was observed in the electronic states of O and assigned to the defects and increase in adsorbed oxygen species. Similarly, a red shift was also observed in the band edge absorption after CuO modification arising due to defects. The sensor film showed an overall n-type character as confirmed using I(V) characteristics. Interestingly, sensor response kinetics towards H2S were enhanced after CuO modification. The highest sensor response value of 298 was measured towards 10 ppm H2S at 150°C for CuO:ZnO NWs sample having 1.26 at % of Cu. This improved sensor response has been attributed mainly to the formation of randomly distributed p–n nano-hetero-junctions between p-type CuO and n-type ZnO over the sensor surface. In particular, the p–n nano-hetero-junctions collapsed due to conversion of semiconducting CuO into metallic CuS after the unique interaction with H2S.

In situ ambient pressure XPS study of Pt/Cu(111) single-atom alloy in catalytically relevant reaction conditions

The presence of multiple reactant gases as well as reaction intermediates in a heterogeneous catalytic reaction results in a complex interaction between different components of the catalyst with each gas, which can alter the surface and chemical state of the catalyst differently than in the presence of an individual gas alone. In this study, we used in situ ambient pressure x-ray photoelectron spectroscopy to study the surface state of Pt/Cu(111) single-atom alloy model system in two catalytically relevant reaction conditions: CO2 hydrogenation and CO oxidation. We found that the activation of CO2 results in the formation of CO, which adsorbs on Pt sites at up to 400 K. In the presence of CO2 and H2, Pt catalyzes the reverse water–gas shift reaction, which produces more CO and further stabilizes surface Pt atoms at 450 K. On the other hand, in CO oxidation condition, the presence of O2 results in the formation of a thick Cu2O layer at higher temperatures, and Pt atoms are no longer detected in the surface and subsurface layers. When O2 is introduced to the sample before CO, the formation of a complete Cu2O layer that covers all Pt atoms occurs immediately at room temperature. However, when CO is introduced at room temperature before O2, the presence of adsorbed CO on Pt sites stabilizes the surface Pt atoms and prevents the formation of a complete Cu2O layer, thus exposing the Pt atoms in ‘holes’ in the Cu2O layer.

Near-white light-emitting diode from p-CuO/n-GaN heterojunction with an i-CuO electron blocking layer

• Near-white LED based on p-CuO/i-CuO/n-GaN was realized by magnetron sputtering and annealing treatment. • CuO could be used as hole injection layer and electron blocking layer under different annealing condition. • The chromaticity coordinates and related color temperatures of the devices were about (0.2381, 0.2606) and 22,505 K. • The i-CuO layer could improve the stability of electron injection and optimize the structure of diode. White light-emitting diodes (WLEDs) have advantages of high efficiency, energy saving, and long working-life, which are ideal choice for next generation of solid-state light sources. Herein we fabricated the near-white light-emitting diode based on the structure of p-CuO/i-CuO/n-GaN heterojunction by magnetron sputtering and annealing treatment. The surface morphology, crystal quality and electrical properties of the CuO layer were investigated by X-ray diffractometer, field emission-scanning electron microscope and Hall measurement. And the influence of the CuO electron blocking layer (EBL) on the diode characteristics were discussed. The current-voltage (I-V) characteristics of those diodes revealed typical p-n junction. Compared with p-CuO/n-GaN heterjunction diode, the EL spectrum of p-CuO/i-CuO/n-GaN heterjunction diode exhibited blue shift and higher intensity. It was found that the addition of CuO EBL enhanced the stability of the diode through analyzing the I-V and EL properties of the diodes. Moreover, at the injection current of 50 mA, the chromaticity coordinates of p-CuO/n-GaN and p-CuO/i-CuO/n-GaN heterojunction diodes are about (0.2686, 0.3334) and (0.2381, 0.2606), and the color temperature are 9205 K and 22,505 K, respectively. Eventually, the EL working mechanism of the two diodes was analyzed in the aspect of the energy band diagram. This study demonstrates the possibility of p-CuO/n-GaN heterojunction with an i-CuO electron blocking layer and their potentials for applications in WLEDs.

Metal-Loaded Mesoporous MCM-41 for the Catalytic Wet Peroxide Oxidation (CWPO) of Acetaminophen

MCM-41 based catalysts (molar ratio Si/Al = 40) were prepared by a hydrothermal route, modified by ionic exchange with different metals (Cu, Cr, Fe and Zn) and finally calcined at 550 °C. The catalysts were fully characterized by different techniques that confirmed the formation of oxides of the different metals on the surfaces of all materials. Low-angle X-ray diffraction (XRD) analyses showed that calcination resulted in the incorporation of metallic Zn, Fe and Cr in the framework of MCM-41, while in the case of Cu, thin layers of CuO were formed on the surface of MCM-41. The solids obtained were tested in the catalytic wet peroxide oxidation (CWPO) of acetaminophen at different temperatures (25–55 °C). The activity followed the order: Cr/MCM-41 ≥ Fe/MCM-41 > Cu/MCM-41 > Zn/MCM-41. The increase of the reaction temperature improved the performance and activity of Cr/MCM-41 and Fe/MCM-41 catalysts, which achieved complete conversion of acetaminophen in short reaction times (15 min in the case of Cr/MCM-41). Fe/MCM-41 and Cr/MCM-41 were submitted to long-term experiments, being the Fe/MCM-41 catalyst the most stable with a very low metal leaching. The leaching results were better than those previously reported in the literature, confirming the high stability of Fe/MCM-41 catalysts synthesized in this study.

Atmospheric pressure plasma reduction of copper oxide to copper metal

Copper oxide films were reduced to copper with an atmospheric pressure argon and hydrogen plasma at temperatures between 25 and 300 °C. A 50-nm-thick CuO layer on a Cu-coated Si wafer, 200 mm in diameter, was fully reduced by the plasma in 200 s at 200 °C. The activation energy for the reaction was found to be 3.7 kcal/mol. X-ray photoelectron spectroscopy confirmed that the copper oxide was reduced to metallic copper. Cross-sectional scanning electron microscopy revealed that voids appeared between the oxide and the base metal layer when the CuO was thicker than 20 nm. These voids remained at the interface after reduction of the copper oxide back to copper metal.

CuO/CuBi2O4 bilayered heterojunction as an efficient photocathode for photoelectrochemical hydrogen evolution reaction

The poor photostability and low photoactivity are two bottlenecks limiting the application of CuO and CuBi2O4 as competitive candidates for photoelectrochemical (PEC) hydrogen evolution reaction (HER). To overcome the bottlenecks, we constructed a novel CuO/CuBi2O4 bilayered structure for PEC HER. The underlying CuO layer functions as the main photoabsorber, while the outside CuBi2O4 layer acts as a protection shield. After further decorated with the NiOx electrocatalysts, the CuO/CuBi2O4/NiOx photocathode exhibits a high photoactivity and remarkable photostability. We ascribe this excellent performance to the following factors: (1) the bilayer structure improves light harvesting efficiency, (2) the outside CuBi2O4 enhances the photostability, (3) the favorable band alignment increases charge separation efficiency, and (4) the presence of NiOx facilitates the charges transfer at the interface. Therefore, this work not only sets a new benchmark efficiency for the CuO and CuBi2O4 heterojunction, but also provides principles for designing layered heterojunction for PEC water splitting.

Investigation on the corrosion resistance of the CuO-Al2O3 composite coating prepared by micro-arc oxidation

A CuO-Al2O3 composite coating was obtained by an AC deposition and a followed secondary MAO treatment in an acidic copper sulfate electrolyte and an alkaline sodium hexametaphosphate electrolyte. Analyzes on phase and elemental composition and microstructure showed that a continuous CuO layer was formed on the top of the original MAO coating. EIS test suggested that after a secondary MAO treatment for 1 min, the samples obtained by AC deposition for 5 min had the best corrosion resistance, because of the barrier of CuO layer to the NaCl solution.

Growing Nanostructured CuO on Copper Foil via Chemical Etching to Upgrade Metallic Lithium Anode.

Metallic lithium is one of the most promising anode materials to build next generation electrochemical power sources such as Li-air, Li-sulfur, and solid-state lithium batteries. The implementation of rechargeable Li-based batteries is plagued by issues including dendrites, pulverization, and an unstable solid electrolyte interface (SEI). Herein, we report the use of nanostructured CuO in situ grown on commercial copper foil (CuO@Cu) via chemical etching as a Li-reservoir substrate to stabilize SEI formation and Li stripping/plating. The lithiophilic interconnected CuO layer enhances electrolyte wettability. Besides, a mechanically stable Li2O- and LiF-rich SEI is generated on CuO@Cu during initial discharge, which permits dense and uniform lithium deposition upon subsequent cycling. Compared with bare Cu, the CuO@Cu electrode exhibits superior performance in terms of Coulombic efficiency, discharge/charge overpotentials, and cyclability. By pairing with the Li-CuO@Cu anodes, full cells with LiFePO4 and LiNi1/3Mn1/3Co1/3O2 cathodes sustain 300 cycles with 98.8% capacity retention at 1 C and deliver a specific capacity of 80 mAh g-1 at 10 C, respectively. This work would shed light on the design of advanced current collectors with SEI modulation to upgrade lithium anodes.

Improving Photoresponsivity of ZnO Nanorods Film by a Combination Doping with Nickel and Adding Cu<sub>2</sub>O Layer

ZnO Nanorods (NRs) is an excellent material for optoelectronic applications. However, ZnO NRs have a wide bandgap. To overcome this problem, ZnO Nanorods has been doped with nickel (0, 3, and 7 at.%) and then coated by a Cu2O layer. The ZnO nanorods were first prepared using a hydrothermal method where nickel of varying concentration was added as a dopant. The prepared samples were then coated by Cu2O using a Chemical Bath Deposition (CBD) method. The fabricated composites were characterized by XRD to identify the phase compositions, SEM-EDX to determine the morphology and elemental compositions, UV-Vis spectroscopy to determine the bandgap, and photocurrent response test to study the sample's response to light. The XRD reveals that the pristine ZnO and Ni-doped ZnO have the same diffraction patterns but the peaks shift to the right with increasing dopant concentrations. The SEM images of all samples show ZnO NRs grew perpendicular to the substrate while its EDX spectra confirm the presence of Nickel in the Ni-doped samples. The UV-Vis spectra showed that the calculated bandgap decreases from ~ 3.2 to 2.7 eV by increasing nickel dopant concentration and adding Cu2O layer. The photocurrent response measurement shows that the ITO/Zn0.93Ni0.07O/Cu2O sample had a good response to light compared to the two other samples.

Chiral CuO@Ni with continuous macroporous framework and its high catalytic activity for electrochemical water oxidation

Electrochemical water splitting is considered as a promising approach to storing renewable electricity in the form of hydrogen fuel. In this work, we report the design and electrocatalytic properties of chiral CuO@Ni with three dimensional (3D) continuous macroporous framework. With the chiral CuO@Ni as anode, the OER overpotential required to achieve the current density of 10 mA/cm2 was as low as 110 mV in 0.1 M KOH electrolyte, and the hydrogen production rate of water splitting reaction could reach 1070 nL/s. Moreover, the OER overpotential could be regulated easily by controlling the deposition time of chiral CuO layer on Ni. The high catalytic activity of chiral CuO@Ni for water splitting is closely associated with the Chiral-induced spin selectivity (CISS) effect, the large reactive area provided by its 3D macroporous structure, and the effective cooperation between chiral CuO and Ni foam that facilitated the transportation of spin aligned electrons from chiral CuO layer to Ni. The results shown in this work indicate a simple and promising strategy to improve the electrocatalytic activity of other chiral earth-abundant catalysts for water splitting.

CuWO4 with CuO and Cu(OH)2 Native Surface Layers for H2S Detection under in-Field Conditions.

The paper presents the possibility of detecting low H2S concentrations using CuWO4. The applicative challenge was to obtain sensitivity, selectivity, short response time, and full recovery at a low operating temperature under in-field atmosphere, which means variable relative humidity (%RH). Three different chemical synthesis routes were used for obtaining the samples labeled as: CuW1, CuW2, and CuW3. The materials have been fully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). While CuWO4 is the common main phase with triclinic symmetry, different native layers of CuO and Cu(OH)2 have been identified on top of the surfaces. The differences induced into their structural, morphological, and surface chemistry revealed different degrees of surface hydroxylation. Knowing the poisonous effect of H2S, the sensing properties evaluation allowed the CuW2 selection based on its specific surface recovery upon gas exposure. Simultaneous electrical resistance and work function measurements confirmed the weak influence of moisture over the sensing properties of CuW2, due to the pronounced Cu(OH)2 native surface layer, as shown by XPS investigations. Moreover, the experimental results obtained at 150 °C highlight the linear sensor signal for CuW2 in the range of 1 to 10 ppm H2S concentrations and a pronounced selectivity towards CO, CH4, NH3, SO2, and NO2. Therefore, the applicative potential deserves to be noted. The study has been completed by a theoretical approach aiming to link the experimental findings with the CuW2 intrinsic properties.

Influence of a Cu2O hole-transport layer on perovskite solar cellscharacteristics

The article is devoted to the creation of a model of a perovskite solar cell with the FTO/TiO2/CH3NH3PbI3-xClx/Cu2O/Au structure in the SCAPS-1D numerical simulation pro-gram. The effect of the thickness of the CH3NH3PbI3-xClxperovskite layer, as well as the thick-ness, concentration of acceptors, and hole mobility in the Cu2O layer on the photoelectric characteristicsof solar cells has been studied. It was found that the optimal thickness of the perovskite layer is 600–700 nm. An increase in the thickness of the Cu2O layer from 50 nm to 500 nm does not have a significant effect on the efficiency of the solar cell, while the optimal concentration of acceptors in the Cu2O layer is 1018–1019cm-3, and the holemobility should be more than 0.1 cm2/Vs. It is shown that a perovskite solar cell with a hole conductive layer Cu2O has better characteristics compared to the Spiro-OMeTAD layer and has the highest effi-ciency of 21.55%

Boosting light harvesting and charge separation of WO3 via coupling with Cu2O/CuO towards highly efficient tandem photoanodes.

Photoanodes based on semiconductor WO3 have been attractive due to its good electron mobility, long hole-diffusion length, and suitable valence band potential for water oxidation. However, the semiconductor displays disadvantages including a relatively wide bandgap, poor charge separation and transfer, and quick electron–hole recombination at the interface with the electrolyte. Here we present a significantly improved photoanode with a tandem structure of ITO/WO3/Cu2O/CuO, which is prepared first by hydrothermally growing a layer of WO3 on the ITO surface, then by electrodepositing an additional layer of Cu2O, and finally by heat-treating in the air to form an exterior layer of CuO. Photocurrent measurements reveal that the prepared photoanode produces a maximum current density of 4.7 mA cm−2, which is, in comparison, about 1.4 and 5.5 times the measured values for ITO/WO3/Cu2O and ITO/WO3 ones, respectively. These enhancements are attributed to (1) harvested UV, visible, and NIR light of the solar spectrum, (2) accelerated charge separation at the heterojunction between WO3 and Cu2O/CuO, (3) better electrocatalytic activity of formed CuxO than pure Cu2O, (4) formation of a protective layer of CuO. This study thus may lead to a promising way to make high-performance and low-cost photoanodes for solar energy harvesting.

Copper Black Coatings for the Absorption of Solar Concentration With an APPJ SiO2 Super-Hydrophobic Protection

Solar thermal energy can be captured on absorbent surfaces, but coatings tend to deteriorate, due to changes in hue, thermal shocks, or detachment of all layers. There is a great challenge in reducing the deterioration because of environmental factors such as corrosion, impact, and dust control, among others. The absorbent coatings interact with the incident solar radiation transforming it as heat energy, and selectivity allows a low emissivity. In this work, a three-layer system on copper is proposed. An anodized CuO or black copper layer as an absorbent with high absorptance is proposed. A protective layer was added to extend the lifetime of use while preserving the functional characteristics of the absorbent black layer by using SiO2 deposited by atmospheric pressure plasma jet (APPJ) using hexamethyldisiloxane. A selective layer of aluminum was deposited by physical vapor deposition (PVD). Thermal shocks were applied by concentrated solar power with a Fresnel lens to represent sudden temperature changes in the radiation absorbent when the weather changes.