Cu2O Clusters Research Articles

Boosting energy storage via the strong interaction between Cu2O clusters and carbon rich framework

Metal oxides have attracted tremendous attention because of their easy fabrication, high reversible voltage, and decent electrochemical capacity in lithium ion batteries. However, the conversion of their structure and the low electric conductivity always lead to a high polarization and poor cyclic stability. Herein, the strong interaction between Cu2O and porous carbon-rich framework is constructed through an in-situ synthesis method. Benefit from the synergistic effect derived from this interaction, the confined size and the high reversibility in chemical reaction of Cu2O are realized. In the hybrid system, the conjugated carbon skeleton with acetylene bond plays crucial role not only in building strong interactions, but also in interconnecting numerous Cu2O clusters for the transport of charge and storing of ions in a homogeneous solid. Hence, the composite material of porous carbon-rich material and Cu2O electrode delivers a decent capacity of 804 and 305 mAh g–1 in lithium and sodium ion batteries, respectively. These results suggest the great potential of such carbon framework/metal oxides composite material applied for high performance battery.

Confined CuⅠ sites in partially electro-reduced 2D conductive Cu-MOF film for boosting CO2 electrocatalysis to C2 products

Cu-based catalysts, especially co-sites of Cu0 and CuⅠ, are the best competitors for electrochemical CO2 fixation to produce multi-carbon (C2 + ) products. However, it is challenging to construct highly stable CuⅠ sites due to the changeability of its valence state and electronic structure in the electroreduction process, and the mechanism is also elusive. Herein, a 2D conductive CuⅡ-MOF film (CuⅡHHTP@Cu0) is prepared on Cu (100) foil by in-situ electrochemical assembly. After pre-reduction, the in-situ produced Cu2O clusters are confined in the cavities of the film created by the local breaking of the MOF framework to construct a unique CuⅠ-CuⅡHHTP@Cu0 catalyst, so that a novel strategy is proposed to stablize highly dispersed CuⅠ sites during electrochemical reduction, thus protecting the Cu2O clusters from further reduction and ensuring the coexistence of CuⅠ (111)-Cu0 (100) sites. As such, the current density of CO2 electrochemical reduction catalyzed by this catalyst exceeds 300 mA cm−2, the duration overs 50 h, and the C2 selectivity achieves 72.6 %. In-situ spectroscopy and theoretical calculations reveal that the optimized microenvironment of the CuⅠ (111) sites reduces the energy barrier of *OCCOH coupling, and Cu0 (100) sites increase the coverage of *CO, thus boosting the production of C2 products.

Red Carbon Mediated Formation of Cu2O Clusters Dispersed on the Oxocarbon Framework by Fehling's Route and their Use for the Nitrate Electroreduction in Acidic Conditions.

The oligomers of carbon suboxide, known as red carbon, exhibit a highly conjugated structure and semiconducting properties. Upon mild heat treatment, it transforms into a carbonaceous framework rich in oxygen surface terminations, called oxocarbon. In this study, the abundant oxygen functionalities are harnessed as anchors to create oxocarbon-supported nanohybrid electrocatalysts. Starting with single atomic Cu (II) strongly coordinated to oxygen atoms on red carbon, the Fehling reaction leads to the formation of Cu2O clusters. Simultaneously, a covalent oxocarbon framework emerges via cross-linking, providing robust support for Cu2O clusters. Notably, the oxocarbon support effectively stabilizes Cu2O clusters of very small size, ensuring their high durability in acidic conditions and the presence of ammonia. The synthesized material exhibits a superior electrocatalytic activity for nitrate reduction under acidic electrolyte conditions, with a high yield rate of ammonium (NH4 +) at 3.31mmolh-1mgcat -1 and a Faradaic efficiency of 92.5% at a potential of -0.4V (vs RHE).

Inactivation and spike protein denaturation of novel coronavirus variants by CuxO/TiO2 nano-photocatalysts

In order to reduce infection risk of novel coronavirus (SARS-CoV-2), we developed nano-photocatalysts with nanoscale rutile TiO2 (4–8 nm) and CuxO (1–2 nm or less). Their extraordinarily small size leads to high dispersity and good optical transparency, besides large active surface area. Those photocatalysts can be applied to white and translucent latex paints. Although Cu2O clusters involved in the paint coating undergo gradual aerobic oxidation in the dark, the oxidized clusters are re-reduced under > 380 nm light. The paint coating inactivated the original and alpha variant of novel coronavirus under irradiation with fluorescent light for 3 h. The photocatalysts greatly suppressed binding ability of the receptor binding domain (RBD) of coronavirus (the original, alpha and delta variants) spike protein to the receptor of human cells. The coating also exhibited antivirus effects on influenza A virus, feline calicivirus, bacteriophage Qβ and bacteriophage M13. The photocatalysts would be applied to practical coatings and lower the risk of coronavirus infection via solid surfaces.

Enhanced the combustion performance of DAP-4 with assembled Cu2O nanoclusters

In this work, the catalytic combustion performance of molecular perovskite energetic material DAP-4 with assembled Cu2O nanoclusters added was studied. Results showed that aggregated spherical Cu2O clusters with the size of ∼1 μm were assembled by nano particles with ∼50 nm diameter by the high-temperature reduction method. Assembled Cu2O nanoclusters have intrinsic catalysis combustion characteristics on DAP-4. With 5 wt% Cu2O added, the combustion time of DAP-4 had reduced by ∼70 ms from raw DAP-4 (∼90 ms) to DAP-4/Cu2O (20 ms). The combustion pressurization rate of DAP-4/Cu2O is ∼4 times of DAP-4. The catalysis combustion mechanism of DAP-4 with assembled Cu2O nanoclusters as an additive was proposed. The work offered a new idea to utilize novel catalysts for enhancing the combustion performance of DAP-4.

Controlled growth of ultrasmall Cu2O clusters on TiO2 nanoparticles by atmospheric-pressure atomic layer deposition for enhanced photocatalytic activity

This work presents a gas-phase approach for the synthesis of Cu2O/TiO2 powder-based photocatalysts using atomic layer deposition (ALD). The process is carried out in a fluidized bed reactor working at atmospheric pressure using (trimethylvinylsilyl)-hexafluoroacetulacetonate copper(I) as the Cu-precursor and H2O vapor as the oxidizer. The saturating regime of the chemical reactions and the linear growth of ALD are achieved. In combination with the unsaturated regime, the ALD approach enables the deposition of ultrasmall Cu2O clusters with average diameters in the range of 1.3–2.0 nm, narrow particle size distributions and tunable Cu2O loadings on P25 TiO2 nanoparticles. The photocatalytic performance of Cu2O/TiO2 photocatalysts is investigated by the degradation of organic dyes, including Rhodamine B (RhB), methyl orange, and methylene blue; the results demonstrate that the surface modification of TiO2 nanoparticles by Cu2O nanoclusters significantly enhances the photocatalytic activity of TiO2. This is attributed to the efficient charge transfer between Cu2O and TiO2 that reduces the charge recombination. The photocatalytic reaction mechanism is further investigated for the degradation of RhB, revealing the dominating role of holes, which contribute to both direct hole oxidation and indirect oxidation (i.e. via the formation of hydroxyl radicals). Our approach provides a fast, scalable and efficient process to deposit ultrasmall Cu2O clusters in a controllable fashion for surface engineering and modification.

Small-sized cuprous oxide species on silica boost acrolein formation via selective oxidation of propylene

Oxide-supported copper-containing materials have attracted considerable research attention as promising candidates for acrolein formation. Nevertheless, the elucidation of the structure-performance relationships for these systems remains a scientific challenge. In this work, copper oxide clusters deposited on a high-surface-area silica support were synthesized via a deposition-precipitation approach and exhibited remarkable catalytic reactivity (up to 25.5% conversion and 66.8% selectivity) in the propylene-selective oxidation of acrolein at 300 °C. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy combined with X-ray absorption fine structure measurements of the catalyst before and after the reaction confirmed the transformation of the small-sized copper oxide (CuO) clusters into cuprous oxide (Cu2O) clusters. With the aid of in situ X-ray diffraction and in situ dual beam Fourier transform infrared spectroscopy (DB-FTIR), the allyl intermediate (CH2=CHCH2*) was clearly observed, along with the as-formed Cu2O species. The intermediate can react with oxygen atoms from neighboring Cu2O species to form acrolein during the catalytic process, and the small-sized Cu2O clusters play a crucial role in the generation of acrolein via the selective oxidation of propylene.

Influence of deposition temperature on the properties of sputtered films grown from a Cu2O[sbnd]CdO[sbnd]TeO2 composite target: Electronic properties of CdTe2O5

Thin films were grown by sputtering targets made by compressing a mixture of the binary oxides Cu2O, CdO and TeO2. Their properties were studied as a function of the substrate temperature, which was varied from room temperature up to 450 °C. All the analyses were carried out on as-grown films. The elemental composition was analyzed by energy dispersive spectroscopy. A structural analysis was carried from grazing-angle X-ray diffraction patterns, which showed the formation of Cu2O (at 350 °C and above) and CdTe2O5 (at 400 °C and above) clusters immersed in an amorphous background. Raman scattering (room temperature) and photoluminescence (room temperature and 80 K) spectra were dominated by the signals originating from the Cu2O clusters. The optical transmittance spectra presented characteristics in agreement with the phases present in the films, as determined by X-ray diffraction. Due to the lack of information on CdTe2O5 in the literature, density functional theory calculations were carried out to analyze the optical properties of the films containing this compound in terms of the calculated electronic band structure. It was determined that CdTe2O5 is an indirect gap material. The theoretical band gap was 3.06 eV, which compares well with the experimental one ∼3.16 eV.

Green Cu2O/TiO2 heterojunction for glycerol photoreforming

Abstract A rapid and sustainable route for synthesizing a green photocatalyst based on nanometric Cu2O clusters dispersed on TiO2 (≈ 2 wt%) was developed. These nanoclusters were synthesized using reducing sugars (0.85 wt%) from aqueous onion waste (Allium cepa) as reducing and stabilizing agent. All this under microwave irradiation. Green photocatalysts produced hydrogen through glycerol photoreforming, ca. 4.7 mmol H2/gcat. The recyclability and reusability of these materials were demonstrated and the achieved heterojunction between Cu2O and TiO2 exhibited a bandgap within the visible spectrum at 2.80 eV, showing potential feasibility to solarize this process.

The surface plasmon-induced hot carrier effect on the catalytic activity of CO oxidation on a Cu2O/hexoctahedral Au inverse catalyst.

The intrinsic correlation between an enhancement of catalytic activity and the flow of hot electrons generated at metal-oxide interfaces suggests an intriguing way to control catalytic reactions and is a significant subject in heterogeneous catalysis. Here, we show surface plasmon-induced catalytic enhancement by the peculiar nanocatalyst design of hexoctahedral (HOH) Au nanocrystals (NCs) with Cu2O clusters. We found that this inverse catalyst comprising a reactive oxide for the catalytic portion and a metal as the source of electrons by localized surface plasmon resonance (localized SPR) exhibits a change in catalytic activity by direct hot electron transfer or plasmon-induced resonance energy transfer (PIRET) when exposed to light. We prepared two types of inverse catalysts, Cu2O at the vertex sites of HOH Au NCs (Cu2O/Au vertex site) and a HOH Au NC-Cu2O core-shell structure (HOH Au@Cu2O), to test the structural effect on surface plasmons. Under broadband light illumination, the Cu2O/Au vertex site catalyst showed 30-90% higher catalytic activity and the HOH Au@Cu2O catalyst showed 10-30% higher catalytic activity than when in the dark. Embedding thin SiO2 layers between the HOH Au NCs and the Cu2O verified that the dominant mechanism for the catalytic enhancement is direct hot electron transfer from the HOH Au to the Cu2O. Finite-difference time domain calculations show that a much stronger electric field was formed on the vertex sites after growing the Cu2O on the HOH Au NCs. These results imply that the catalytic activity is enhanced when hot electrons, created from photon absorption on the HOH Au metal and amplified by the presence of surface plasmons, are transferred to the reactive Cu2O.

Cu2O clusters decorated on flower-like TiO2 nanorod array film for enhanced hydrogen production under solar light irradiation

Abstract In this work, the TiO2 nanorod arrays (TNAs), TNAs/Cu2O-10CYC, and TNAs/Cu2O-30CYC composites photo-catalysts for solar water splitting anode was successfully prepared via cyclic impregnation growth method. The structure, surface morphology and element chemical states have been investigated and discussed in detail. The UV–vis and PL results confirm that interaction has been formed between TNAs and Cu2O in the composite photo-catalysts and the TNAs/Cu2O composites exhibit broad spectrum absorption. Three factors affecting on the enhancement of solar light hydrogen production efficiency, e.g. enhanced UV-light absorption in solar spectrum, massive charge carrier generation and improved surface-interface reaction due to the absorbing visible light by the narrow band gap Cu2O and the injecting electrons into TiO2 conduction band, are proposed based on the experimental results. The TNAs/Cu2O-10CYC composite samples exhibit highest enhanced photocatalytic activities in the hydrogen production, which H2 evolution efficiency is about 4-fold higher than that of pure TNAs. It indicates that the efficient photo generated electron-hole transformation and separation in TNAs/Cu2O-10CYC composite sample leads to the improvement of photocatalytic performance. The present study provides a new light to prepare TNAs/Cu2O of novel configuration with promising potential applications.

Formation of Cu2O/Titanate/Titania Heterojunctions from Hydrothermally Induced Dual Phase Transitions

A microwave-assisted hydrothermal method has been developed as an efficient approach to readily induce phase transition of titanate assemblies in conjunction with decoration of Cu2O clusters on the surface. The influence of Cu2+ ions on the hydrothermally induced structural evolution was examined, and the roles of heterojunctions in the resulting composites in charge separation for improved photocatalytic activity were clarified. Hierarchical titanate assemblies with high adsorption capacity for Cu2+ ions (95.7 mg/g) were prepared from a low alkaline condition. Microwave-assisted hydrothermal treatment was then used to transform the adsorbents into Cu2O/titanate/titania photocatalysts in 20 min via inducing titanate-to-titania and Cu2+-to-Cu2O dual transitions. While tubular architecture was maintained in the composites, the Cu2O clusters highly dispersed on the surface. Adsorbed Cu2+ ions have been found to retard the titanate-to-titania transformation locally, thus leading to Cu2O/titanate/titania heter...

Titanium‐Microfiber‐Supported Binary‐Oxide Nanocomposite with a Large Highly Active Interface for the Gas‐Phase Selective Oxidation of Benzyl Alcohol

AbstractThin‐sheet sinter‐locked Ti‐microfiber‐supported binary‐oxide‐nanocomposite catalysts engineered on the micro‐ to macroscales were developed for the gas‐phase aerobic oxidation of benzyl alcohol to benzaldehyde. The catalysts demonstrated higher activity than single‐oxide and noble‐metal catalysts with good stability and regenerability. The catalysts were obtained by placing transient metal (e.g., Ni, Co, Cu, Mn) nitrates onto a Ti‐microfiber surface by impregnation, and the supported nitrates were subsequently in situ transformed into the binary‐oxide composites in the real reaction stream at 300 °C. Among them, CoO‐2.5–CuOx‐2.5/Ti‐fiber was found to be the best catalyst; it delivered 93.5 % conversion of benzyl alcohol (b.p. 210 °C) with 99.2 % selectivity to benzaldehyde at 230 °C. In situ induced formation of “CoO@Cu2O” ensembles (i.e., larger CoO nanoparticles partially covered with smaller Cu2O clusters and/or nanoparticles) was identified, which by nature resulted in a large Cu2O–CoO interface and led to a significant improvement in the low‐temperature activity.

Electrochemical behavior of eugenol on TiO2nanotubes improved with Cu2O clusters

TiO2 nanotubes incorporated with Cu2O clusters (Cu2O-TiNTs) were synthesized and employed as a probe for the rapid and sensitive voltammetric determination of eugenol. The electrochemical behavior of eugenol on the electrodes modified with Cu2O-TiNTs was explored systematically using cyclic voltammetry as a function of concentration of eugenol, scan rate, Cu2O content, and calcination temperature, respectively. Furthermore, the electrochemical response mechanism on these modified electrodes was discussed preliminarily. The results indicate that the electrodes coated with Cu2O-TiNTs possess high sensitivity to eugenol with a detectable concentration of 1.3 × 10−6 mol L−1. Here, the tubular structure of TiO2 nanotubes plays a key role in the electrochemical performance of Cu2O-TiNTs. The TiO2 nanotubes serve as an electron-transfer channel to enhance the electron transfer between eugenol molecules and electrode surface. Meanwhile, the Cu2O clusters serve as a promoter to further make the electron transfer more efficient and as a stabilizer to avoid change of the tubular structure of TiO2 nanotubes during calcination.

Oxygen release kinetics and mechanism study on Cu-, Co-, Mn-based oxygen carrier

Sol-gel derived CuO/CuAl2O4, Co3O4/CoAl2O4 and Mn2O3/Al2O3 oxygen carriers were studied in a fluidized bed reactor under CO2 atmosphere, where the oxygen release characteristics under different temperatures were focused. The mechanism function and kinetics parameters in the oxygen release were obtained from the experimental data. In the process of oxygen release, the phases of CuO and CuAl2O4 performing as active components decompose to Cu2O and CuAlO2 with O2 generation. While, only Co3O4 and Mn2O3 can release oxygen in Co3O4/CoAl2O4 and Mn2O3/Al2O3 oxygen carriers, in which Co3O4 and Mn2O3 are respectively reduced to CoO and Mn3O4; and CoAl2O4 and Al2O3 perform as inert carrier. The kinetic analysis shows that the oxygen release of three oxygen carriers can be described by the nucleation and nuclei growth model. This means that after O2 release the Cu-O bond (as an example) in the oxygen carrier is broken, generates Cu2O active sites diffusing away from the reduction centers, and comes together to form Cu2O clusters. The mechanism function G(x), the activation energy and the pre-exponential factor have different expressions or different values for different oxygen carriers. The activation energies in the oxygen release of CuO/CuAl2O4, Co3O4/CoAl2O4 and Mn2O3/Al2O3 oxygen carriers, are 226.37, 130.06 and 65.90 kJ/mol respectively; and the pre-exponential factors are 2.99×106 s−1, 4.96×103 s−1 and 27.37 s−1 respectively.

Embedded Palladium Activation as a Facile Method for TiO2‐Nanotube Nanoparticle Decoration: Cu2O‐Induced Visible‐Light Photoactivity

Embedded Palladium Activation as a Facile Method for TiO₂‐Nanotube Nanoparticle Decoration: Cu₂O‐Induced Visible‐Light Photoactivity

Morphology, orientation relationship, and stability analysis of Cu2O nanoclusters on SrTiO3 (100)

Reflection high energy electron diffraction, atomic force microscopy, and theoretical studies based on classical nucleation theory have been used to interpret the morphology, orientation relationship, and stability of Cu2O nanoclusters on SrTiO3 (100) (STO). We propose that the competing interfacial and elastic energies facilitate an in-plane rotation of the Cu2O clusters by 45° with respect to the STO substrate and stabilize Cu2O clusters on STO(100) with an orientation relationship of (001)Cu2O//(001)SrTiO3 and ⟨100⟩Cu2O//⟨110⟩SrTiO3. Our preliminary theoretical analysis also suggests that this particular orientation results in smaller critical nucleus sizes and lower nucleation barriers and also indicates a chemical potential (growth rate) dependence of the orientation relationship.

Mechanism of CO oxidation in excess H2 over CuO/CeO2 catalysts: ESR and TPD studies

The oxidation of CO with oxygen over (0.25–6.4)% CuO/CeO2 catalysts in excess H2 is studied. CO conversion increases and the temperature range of the reaction decreases by 100 K as the CuO content is raised. The maximal CO conversion, 98.5%, is achieved on 6.4% CuO/CeO2 at 150°C. At T > 150°C, the CO conversion decreases as a result of the deactivation of part of the active sites because of the dissociative adsorption of hydrogen. CO is efficiently adsorbed on the oxidized catalyst to form CO-Cu+ carbonyls on Cu2O clusters and is oxidized by the oxygen of these clusters, whereas it is neither adsorbed nor oxidized on Cu0 of the reduced catalysts. The activity of the catalysts is recovered after the dissociative adsorption of O2 on Cu0 at T ∼ 150°C. The activation energies of CO, CO2, and H2O desorption are estimated, and the activation energy of CO adsorption yielding CO-Cu+ carbonyls is calculated in the framework of the Langmuir-Hinshelwood model.

Photo reduction of CO2 to methanol via TiO2 photocatalyst

Greenhouse gas such as CO2 is the primary cause of global warming. Alternative energy source should be provided without producing more CO2, such as solar energy. One of the best routes to remedy CO2 is to transform it to hydrocarbons using photo reduction. In our study, CO2 was photocatalytically reduced to produce methanol using a Hg lamp with wavelength 365 nm in a steady‐state optical‐fiber photo reactor. The optical‐fiber photo reactor, comprised of near 120 Cu/TiO2‐coated fibers, was designed and assembled to transmit and spread light uniformly inside reactor. TiO2 film was coated on optical fiber using dip‐coating method. Titania and Cu‐loaded solutions were prepared by a thermal hydrolysis method. The thickness of Cu/TiO2 film was 53 nm and consisted of very fine spherical particle with diameter of near 14 nm. The XRD spectra indicated the anatase phase of all TiO2 and Cu/TiO2 films. The wavelength of absorption edge was on 367 nm, equivalent to near 3.3 eV. Most active Cu species on TiO2 surface were Cu2O clusters, and played an important role for the formation of methanol. The methanol yield increased with UV irradiative intensity. Photo activity increased with increasing Cu loadings. Maximum methanol rate was 0.45 μmole/g‐cat•hr using 1.2 wt%‐Cu/TiO2 catalyst under 16 W / cm2 irradiation, 1.3 bar pressure of CO2, and 5000 seconds mean residence time. Higher than 1.2 wt% Cu loading gave less rate of methanol yield because of the masking effect of Cu2O clusters on the surface of TiO2.