CuO Surface Research Articles

Cu2O-CNF heterojunction for exhaled H2S sensing

Developing a gas sensor for the expedient, rapid, and accurate detection of hydrogen sulfide (H2S) in human exhaled breath at room temperature would offer an opportunity for home-style self-monitoring of some chronic diseases. In this work, Cu2O-carbon nanofiber (CNF) heterojunctions were prepared by a two-dimensional (2D) electrodeposition in-situ assembly method to detect low-concentration H2S gas at room temperature. The heterojunction had a distinct interface, which was confirmed by scanning electron microscopy, transmission electron microscopy and voltammetry tests. The detection limit of the sensor was as low as 5 ppb, and the sensors could directly distinguish the exhaled breath of healthy individuals and simulated patients. We attributed the excellent performances to synergistic effects of the modulation of the heterointerface barrier and the sulfide reaction of Cu2O. Furthermore, the adsorption behaviors of H2S on the surfaces of pure Cu2O and the Cu2O-CNF heterojunction were evaluated using the density functional theory (DFT) based on first principles. The results further confirmed that the formation of the heterostructure enhances the H2S adsorption capacity and electron transfer of the sensitive material. This study is of great significance for the diagnosis and monitoring of diseases with the exhaled H2S biomarker.

Bi-metal-organic framework-derived S-scheme InP/CuO-C heterostructure for robust photocatalytic degradation of ciprofloxacin in a microfluidic photoreactor

The presence of antibiotics in the environment raises significant environmental concerns due to their adverse impact on organisms and the potential transmission of drug-resistant genes. Heterostructure photocatalysts have emerged as a promising remedy for this issue. This study introduces an innovative approach that employs an In/Cu-organic framework (bimetallic-MOF) as a sacrificial precursor for crafting a carbon-supported InP/CuO heterostructure with adjustable band-matching properties. Through comprehensive analyses encompassing structural, morphological, optical, electrochemical, and density functional theory calculations, compelling evidence is presented for the cubic carbon layer housing zinc-blende InP and monoclinic CuO. Furthermore, the existence of an S-scheme charges transfer pathway between InP and CuO is strongly substantiated, significantly enhancing spatial charge separation. The engineered InP/CuO S-scheme nanoheterostructure exhibits exceptional performance and stability under visible light exposure within a custom-designed spiral microfluidic photoreactor (SMPR), achieving an impressive 81.70% degradation of ciprofloxacin – a commonly found antibiotic in wastewater – in just 15 min. The findings from photoelectrochemical and spectroscopic analyses reveal that the InP/CuO S-scheme heterostructure, derived from the bi-MOF, in conjunction with the SMPR, not only exhibits a robust response to visible light, improved carrier mobility, and effective charge separation and transfer, but also enhances mass and photon transfer. Within the S-scheme heterostructure, the process of charge transfer centers on the creation of reactive oxygen species, specifically OH and O2–, on InP and CuO surfaces, correspondingly. These species function as oxidation and reduction photocatalysts, respectively, exerting a pivotal influence in augmenting the overall performance. The findings make substantial contributions towards creating effective and sustainable solutions for mitigating environmental contamination, emphasizing the crucial role of advanced material design and microfluidic reactor engineering in the realm of photocatalysis.

Advanced oxidation using sulfate radicals for the surface oxidation of Cu2O and the separation of copper via acid leaching

The effect of Na2S2O8 on Cu2O surface oxidation and leaching was investigated, and the presence of Na2S2O8 transforms the surface of Cu2O into more easily leachable CuO, resulting in a 35.50% increase in the extraction rate of Cu than that without Na2S2O8. In the acid leaching system, O atoms combined with H+ to form H2O, which was continuously separated from the surface to form vacancies. Cu(I) on the mineral surface formed Cu(0) and Cu(Ⅱ), of which Cu(Ⅱ) separated from the mineral surface and entered the solution, while Cu(0) was reconstructed on the surface, and a Cu-Cu metal bond with a bond length of 2.40 Å was appeared in the DFT calculation, which caused the content of Cu atom on the surface to be higher than that of O atom. After oxidation, high-spin Cu(Ⅱ) contributed by the 3d orbital appeared on the mineral surface. The Cu(Ⅱ) content of the oxidized Cu2O surface was 19.80% higher than that of the pure Cu2O surface, indicating that the copper on the oxidized Cu2O surface was more easily extracted. Moreover, the adsorption energy of chemical adsorption occurring in the presence of oxidant (−1.91 eV) was more negative than that in the absence of oxidant (−0.21 eV).

Exploring the CO2 photocatalytic evolution onto the CuO (1 1 0) surface: A combined theoretical and experimental study

A combined theoretical and experimental study was performed to elucidate the photocatalytic potential of tenorite, CuO (1 1 0) and to assess the evolution pathway of carbon dioxide (CO2) evolution pathway. The calculations were performed with density functional theory (DFT) at a DFT + U + J0 and spin polarized level. The CuO was experimentally synthesized and characterized with structural and optical methodologies. The band structure and density of states revealed the rise of band gaps at 1.24 and 1.03 eV with direct and indirect band gap nature, respectively. These values are in accordance with the experimental evidence at 1.28 and 0.96 eV; respectively, which were obtained by UV-Vis DRS. Such a behavior could be related to enhanced photocatalytic activity among copper oxide materials. Experimental evidence such as SEM images and work function measurements were also performed to evaluate the oxide. The redox potential suggests a catalytic character of tenorite (1 1 0) for the CO2 transformation through aldehydes (methanal) intermediate formation. Furthermore, a route through methylene glycol CH2(OH)2 was also explored with the theoretical methodology. The reaction path exhibits an immediate reduction of ▪ into a •OH radical and an [OH]− anion, in the first step. This •OH radical attacks a double bond (C = O) of ▪ to form bicarbonate ([▪]−) and subsequently, carbonic acid (▪). The carbonic acid reacts with other •OH radical to finally form orthocarbonic acid (▪).

Ag decorated-Cu2O catalysts with enhanced selectivity for CO2 electroreduction toward C2+ products

Copper-based electrocatalysts have been widely used to generate C2+ products via the electrocatalytic carbon dioxide reduction reaction (CO2RR) because the catalysts possess unique properties for C-C coupling. Tandem catalysis is an attractive concept for C2+ production, enhancing selectivity and activity by combining CO-generating catalysts with Cu-based catalysts. Herein, the ability of Ag decoration to improve the selectivity of the Cu2O catalysts for C2+ production was investigated. The Ag/Cu2O catalyst with 10 wt% Ag content on the Cu2O surface (10 Ag/Cu2O) exhibited high Faradaic efficiency (FE) of 48% for C2+ products at –0.99 V (vs. RHE). Moreover, the partial current density of C2+ products on the 10 Ag/Cu2O was improved by 33% compared to the bare Cu2O catalyst. The intermediate (CO) generated on the Ag surface migrates by diffusion and/or sequential desorption-re-adsorption from Ag to Cu at the Ag-Cu interface of the Ag/Cu2O, increasing CO coverage on the Cu surface. The increase in CO coverage on the Cu surface of the Ag/Cu2O catalysts after decoration with Ag effectively reduces the hydrogen evolution reaction (HER), enhancing C-C coupling to generate C2+ products on the Ag/Cu2O. In addition, density functional theory (DFT) calculation results also revealed that Ag provides more CO2 activation sites, increasing CO coverage and reducing hydrogen adsorption energy, thus suppressing HER and improving the selectivity of CO2RR toward C2+ production.

Using adatoms to tune the band structures of Cu2O surfaces for photocatalytic applications

Cuprous oxide (Cu2O) is a highly promising semiconductor with exceptional visible-light photocatalytic activity, and its nanoparticles have significant implications for promoting the Net Zero and Green Energy Economy due to low cost, ease of synthesis, and impressive performance. However, the photocatalytic effectiveness of Cu2O is heavily determined by the adsorbed species and crystal facets, both of which are crucial to the facet engineering of Cu2O. Here we applied first-principles calculations to investigate the geometric and electronic structures, as well as the thermodynamic stabilities, of Cu2O (100), (110), and (111) surfaces upon decoration with H, OH, Na, Cl, and Br units, respectively. We find that H, OH, and halogen atoms are efficient in stabilizing the Cu2O surface. The H atom is an excellent donor regardless of the surface orientation, whereas the roles of Br and Cl atoms as either donors or acceptors depend on specific surface conditions. Notably, the coverage conditions are essential in shaping the electronic properties of the (110) surface, on which the half-coverage OH-terminated surface manifests a suitable band structure facilitating the separation of the electron/hole pairs, thereby enhancing the photocatalytic efficiency. Accordingly, our calculations confirm that these species usually within the synthesis environment also have the ability to engage in the reaction and significantly alter the inherent facet-dependence of electronic structures in Cu2O crystals. These findings can help to elucidate various experimental results observed in Cu2O photocatalysis and can serve as an efficient strategy benefitting photocatalyst design.

Al-Doped Octahedral Cu2O Nanocrystal for Electrocatalytic CO2 Reduction to Produce Ethylene.

Ethylene is an ideal CO2 product in an electrocatalytic CO2 reduction reaction (CO2RR) with high economic value. This paper synthesised Al-doped octahedral Cu2O (Al-Cu2O) nanocrystal by a simple wet chemical method. The selectivity of CO2RR products was improved by doping Al onto the surface of octahedral Cu2O. The Al-Cu2O was used as an efficient electrocatalyst for CO2RR with selective ethylene production. The Al-Cu2O exhibited a high % Faradic efficiency (FEC2H4) of 44.9% at -1.23 V (vs. RHE) in CO2 saturated 0.1 M KHCO3 electrolyte. Charge transfer from the Al atom to the Cu atom occurs after Al doping in Cu2O, optimizing the electronic structure and facilitating CO2RR to ethylene production. The DFT calculation showed that the Al-Cu2O catalyst could effectively reduce the adsorption energy of the *CHCOH intermediate and promote the mass transfer of charges, thus improving the FEC2H4. After Al doping into Cu2O, the center of d orbitals shift positively, which makes the d-band closer to the Fermi level. Furthermore, the density of electronic states increases due to the interaction between Cu atoms and intermediates, thus accelerating the electrochemical CO2 reduction process. This work proved that the metal doping strategy can effectively improve the catalytic properties of Cu2O, thus providing a useful way for CO2 cycling and green production of C2H4.

Efficiently elimination of high concentration dye pollutants by Ph-C≡C-Cu/nanoparticles hybrids

For the requirement of industrial printing and dyeing wastewater treatment, this work designed and synthesized a serious of Ph-C≡C-Cu/nanoparticles (NPs) hybrids for highly efficient removal of dye pollutants. Among them, Cu2O/Ph-C≡C-Cu shows the most excellent adsorption ability and considerable stability. The prepared Cu2O/Ph-C≡C-Cu hybrids were detailedly studied, demonstrating a different growth mode of Ph-C≡C-Cu on the surface of Cu2O, which provides increased surface area and adsorption sites exposure. The highest adsorption capacity of MO achieved 629.1 mg/g at 20 wt% Cu2O/Ph-C≡C-Cu hybrid, which is about 10 and 30 time higher than those of raw Ph-C≡C-Cu and Cu2O. Moreover, it is even 3 times higher than the famous adsorbent activated carbon. This is because that the adsorption mode of MO on the surface of Cu2O/Ph-C≡C-Cu hybrid is demonstrated to be chemical adsorption by the kinetic analysis, while it is mainly physical adsorption on the surface of activated carbon. Besides, Cu2O/Ph-C≡C-Cu hybrid also shows good stability and universality at the condition of basic room temperatures (0–50 °C), pH of 5–11, anions (NO3− and HCOO−) and other dyes (congo red, malachite green and sunset yellow) co-existence. This work indicates that 20 wt% Cu2O/Ph-C≡C-Cu is an effective and prospective adsorbent for treating the printing and dyeing industrial wastewater.

Understanding the role of oxygen-vacancy defects in Cu2O(111) from first-principle calculations

The presence of defects, such as copper and oxygen vacancies, in cuprous oxide films determines their characteristic carrier conductivity and consequently their application as semiconducting systems. There are still open questions on the induced electronic re-distribution, including the formation of polarons. Indeed, to accurately reproduce the structural and electronic properties at the cuprous oxide surface, very large slab models and theoretical approaches that go beyond the standard generalized gradient corrected density functional theory are needed. In this work we investigate oxygen vacancies formed in proximity of a reconstructed Cu2O(111) surface, where the outermost unsaturated copper atoms are removed, thus forming non-stoichiometric surface layers with copper vacancies. We address simultaneously surface and bulk properties by modelling a thick and symmetric slab, to find that hybrid exchange-correlation functionals are needed to describe the oxygen vacancy in this system. Our simulations show that the formation of oxygen vacancies is favoured in the sub-surface layer. Moreover, the oxygen vacancy leads to a splitting and left-shift of the shallow hole states in the gap, which are associated with the deficiency of copper at the surface. These findings suggest that surface electronic structure and reactivity are sensitive to the presence of oxygen vacancies, also when the latter are formed deeper within the film.

Fabrication of CuO (p)–ZnO (n) Core–Shell Nanowires and Their H2-Sensing Properties

Unlike the conventional one-dimensional (1D) core–shell nanowires (NWs) composed of p-type shells and n-type cores, in this work, an inverse design is proposed by depositing n-type ZnO (shell) layers on the surface of p-type CuO (core) NWs, to have a comprehensive understanding of their conductometric gas-sensing kinetics. The surface morphologies of bare and core–shell NWs were investigated by field emission scanning electron microscope (FE-SEM). The ZnO shell layer was presented by overlay images taken by electron dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscopy (HRTEM). The pronounced crystalline plane peaks of ZnO were recorded in the compared glancing incident X-ray diffraction (GI-XRD) spectra of CuO and CuO–ZnO core–shell NWs. The ZnO shell layers broaden the absorption curve of CuO NWs in the UV-vis absorption spectra. As a result of the heterostructure formation, the intrinsic p-type sensing behavior of CuO NWs towards 250 and 500 ppm of hydrogen (H2) switched to n-type due to the deposition of ZnO shell layers, at 400 °C in dry airflow.

Synergistic antibacterial study of nano-Cu2O/CuO@Ag-tetracycline composites

The rapid increase in drug resistance has not reduced the antibacterial activity of most antibacterial drugs but also brought great challenges to society. Therefore, there is an urgent need to develop new antibacterial agents. In this study, copper nitrate trihydrate [Cu(NO3)2·3H2O] was used as a raw material and hydrazine hydrate as a reducing agent to prepare cuprous oxide (Cu2O/CuO). Next, silver nitrate (AgNO3) was added and monomeric silver was loaded on the surface of Cu2O by in situ reduction to obtain Cu2O/CuO@Ag composites. Lastly, nano-Cu2O/CuO@Ag-tetracycline composites were obtained by combining them with tetracycline. Systematic characterization of inhibitors was conducted using transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), and ultraviolet–visible spectroscopy (UV–vis). The inhibitory properties and mechanism of Cu2O/CuO@Ag-tetracycline on the Gram-positive bacterium Staphylococcus aureus (S. aureus), Gram-negative bacterium Escherichia coli (E. coli), and drug-resistant bacterium Salmonella (T-Salmonella) were studied. The inhibition performance study showed that the inhibition rate of Cu2O@CuO@Ag-tetracycline was almost 99.99% against the three tested bacteria at 40 min when used at a concentration of 150 μg/mL. Compared with tetracycline and Cu2O/CuO alone, Cu2O/CuO-tetracycline composites have several times higher antibacterial efficiency against E. coli, S. aureus and T-Salmonella. Moreover, the nano-Cu2O/CuO@Ag-tetracycline composites were most sensitive to E. coli. The inhibition mechanism revealed that the nanocomposites could effectively destroy the cell wall of Gram-negative bacteria, enter the cell interior, inhibit cell respiration, and eventually lead to bacterial rupture and death. The nano-Cu2O/CuO@Ag-tetracycline composites exhibited excellent antibacterial properties, indicating their wide application prospects in the fields of medical devices and medical materials.

Defect-Induced Phase Transformations in CuO Thin Films by Ag Ion Implantation and Their Gas-Sensing Applications

The present study is aimed to modify the structural, optical, and morphological properties of CuO thin films with Ag ion implantation toward their potential applications. Fabrication of thin films of CuO was carried out using a thermal evaporation technique on silicon (Si) substrate; post implantation was done with 30 keV Ag ions with varying fluences from 1 × 1014 to 1 × 1016 ions/cm2. The pristine and implanted samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), and diffused reflectance spectroscopy (DRS). SRIM simulation was also carried out to understand the range and other effects. XRD measurements confirmed the formation of the CuO phase for pristine samples, and with the increase in ion fluence, the chemical composition changed from pure CuO to Cu2O + CuO and then to Cu2O + Cu at higher ion fluences. These experimental results from Raman spectroscopy were also consistent with the XRD analysis, which also showed the presence of mixed phases of CuO, Cu2O, and Cu. Results from AFM showed that the value of average roughness increased due to more defects. DRS results revealed the variation in band-gap energy for pristine and implanted samples from 1.96 to 1.71 eV. Density functional theory (DFT) simulations confirmed that Ag ion implantation causes the reduction of CuO surface into Cu2O and Cu. We found that Ag ion implantation-induced defects lead to the mixed phases of CuO, Cu2O, and Cu, which can help in the selective sensing of ethanol and acetone, demonstrating this as a useful technique and having potential applications in energy conversions, and gas and biomolecule sensing.

Investigation on the Catalytic Cracking Mechanism of CuO on Dimethyl Sulfoxide (C2H6OS) and Surface Modification Effects: Insights from Density Functional Theory Calculations

To explore the catalytic cracking mechanism of CuO on oil shale and the catalytic activity of surface modifications of CuO on oil shale, dimethyl sulfoxide (C2H6OS) is used as a model molecule representative of organic sulfur compounds in oil shale, and the adsorption and dissociation behaviors of C2H6OS molecules on pure and OH pre-adsorbed CuO(111) surfaces were investigated by density functional theory calculations. The results indicate that C2H6OS selectively adsorbs at the Cusub sites via the S atom and decomposes through cleavage of the C–H bond prior to the breaking of the C-S bond on both surfaces. The presence of OH on the CuO(111) surface promoted the dissociation of C2H6OS. The energy barriers of dehydrogenation and desulfurization of C2H6OS on the OH pre-adsorbed CuO(111) surface were 20.0 and 19.3 kcal/mol, respectively, which are 41% and 49% lower than those on pure surfaces. The present results provide crucial guidance for the synthesis and improvement of high-performance pyrolysis catalysts specifically designed for oil shale applications. Additionally, they also present important data regarding to the thermal stability of C2H6OS in the presence of incompatible substances.

Quantitative In Situ Monitoring of Cu-Atom Release by Cu2O Nanocatalysts under Photocatalytic CO2 Reduction Conditions: New Insights into the Photocorrosion Mechanism.

Cu2O is among the most promising photocatalysts for CO2 reduction, however its photocorrosion remains a standalone challenge. Herein, we present an in situ study of the release of Cu ions from Cu2O nanocatalysts under photocatalytic conditions in the presence of HCO3 as a catalytic substrate in H2O. The Cu-oxide nanomaterials were produced by Flame Spray Pyrolysis (FSP) technology. Using Electron Paramagnetic Resonance (EPR) spectroscopy in tandem with analytical Anodic Stripping Voltammetry (ASV), we monitored in situ the Cu2+ atom release from the Cu2O nanoparticles in comparison with CuO nanoparticles under photocatalytic conditions. Our quantitative, kinetic data show that light has detrimental effect on the photocorrosion of Cu2O and ensuing Cu2+ ion release in the H2O solution, up to 15.7% of its mass. EPR reveals that HCO3 acts as a ligand of the Cu2+ ions, promoting the liberation of {HCO3-Cu} complexes in solution from Cu2O, up to 27% of its mass. HCO3 alone exerted a marginal effect. XRD data show that under prolonged irradiation, part of Cu2+ ions can reprecipitate on the Cu2O surface, creating a passivating CuO layer that stabilizes the Cu2O from further photocorrosion. Including isopropanol as a hole scavenger has a drastic effect on the photocorrosion of Cu2O nanoparticles and suppresses the release of Cu2+ ions to the solution. Methodwise, the present data exemplify that EPR and ASV can be useful tools to help quantitatively understand the solid-solution interface photocorrosion phenomena for Cu2O.

Identifying the Local Atomic Environment of the "Cu3+" State in Alkaline Electrochemical Systems.

CuO-based catalysts are active for the oxygen evolution reaction (OER), although the active form of copper for the OER is still unknown. We combine operando Raman experiments and density functional theory (DFT) electronic structure calculations to determine the form of Cu(O)xOHy present under OER conditions. Raman spectra show a distinct feature related to the active "Cu3+" species, which is only present under highly oxidizing conditions. DFT is used to produce theoretical Raman standards and match the unique Raman feature of copper under OER potentials. This method identifies a range of Cu3+-containing compounds which match the distinct Raman feature. We then integrate experimental electrochemistry to progressively eliminate possible structures and determine the stoichiometry of the active form as CuOOH, which likely takes the form of a surface-adsorbed hydroxide on a CuO surface. Bader charge analysis, site-projected wavefunctions, and density of states analysis show that electron density is removed from O 2p orbitals upon hydroxide adsorption, suggesting that the electronic structure exhibits d9L Cu2+ behavior rather than the local electronic structure of a formal Cu3+.

A novel switchable collector for selective flotation of fine copper oxide from silica

A novel pseudo-Gemini collector (PGC) featuring pH-responsive collecting power and enhanced selectivity is developed for flotation recovery of fine copper oxides from silica. The switchable PGC is formed through ionic pairing between protonated triethylenetetramine (TETA) and deprotonated oleic acid (OA) and is referred to as T-OA. The formation of T-OA was characterized by determining its critical micelle concentration of 0.6 mM at pH 10, which is much lower than that of 2.5 mM for its counterpart of OA, demonstrating a stronger surface activity of the novel T-OA collector for hemimicelle formation. Micro-flotation results showed a CuO recovery of over 90% at T-OA concentrations as low as 0.01 mM and pH 10, at which the collector exists in pseudo-Gemini form. Adjusting the flotation pH to 5 switched T-OA to monomeric form of OA with a lower surface activity but a higher selectivity which was further improved by removal of activating ions from silica by TETA. Introducing T-OA of higher collecting power in the rougher stage and then switching to a lower collecting power form of higher selectivity in the subsequent cleaner stage enhanced the flotation separation of fine CuO from silica. Zeta potential measurements indicated adsorption of T-OA on copper oxide at pH 5 and 10 with the hydrophobicity of copper oxide being stronger at alkaline conditions than that at acidic conditions as determined by contact angle measurement. The switchability of T-OA activity on CuO surfaces was illustrated by contact angle and in situ particle size distribution measurements. The reversible adsorption of T-OA on copper oxide at pH 10 was shown by QCM-D results. The results in the current study using switchable T-OA provide a clear direction for design of switchable collectors to achieve the control of the collecting performance and selectivity during the flotation processes, enhanced overall flotation performance.

Enriched oxygen vacancies of copper(I) oxide particles for enhanced removal of hydrogen sulfide at room temperature

In this work, the removal of hydrogen sulfide (H2S) by copper(I) oxide (Cu2O) and copper(II) oxide (CuO) particles synthesized by thermal decomposition (TD) and liquid reduction is investigated in a fixed-bed experiment at 25 °C and 1 atm. The surface oxygen vacancies (VOs) contents of the prepared Cu2O samples are more than twice that of the synthesized CuO particles, which are closely related to H2S removal performance. The H2S adsorption capacity of Cu2O prepared is 135.6 mg g−1, approximately 27 times that of CuO. A dense CuS layer formed on the CuO surface makes it significantly less reactive with H2S than Cu2O. Due to the crystal structure and abundant VOs on the Cu2O surface, the weak Cu–O bonds are broken during the sulfurization process, causing the rupture of the surface layer. And the sulfidation reaction gradually extends to the interior through the cracked surface layer, leading to the excellent sulfurization performance of Cu2O. The larger H2S adsorption capacity of Cu2O prepared by TD than that of Cu2O prepared by liquid reduction could be attributed to the presence of more numbers of VOs and Cu atoms on the surface. Moreover, H2O can enter VOs and promote the dissociation of H2S into S2−, thereby improving H2S adsorption capacity. This work demonstrates that Cu2O is a promising sorbent for H2S removal at room temperature.

Oxygen Vacancy-Mediated Reactivity: The Curious Case of Reduction of Nitroquinoline to Aminoquinoline by CuO

Reduction of nitroarenes is a useful strategy for the preparation of aromatic amines. In this work, CuO was used as a reusable solid reagent for the reduction of nitroquinolines to aminoquinolines using hydrazine monohydrate as the hydrogen donor under mild reaction conditions. The reaction of 0.5 mmol of 5-nitroquinoline to 5-aminoquinoline was completed in 10 min with 100% conversion and selectivity. The reagent CuO could be easily collected and reused for up to four cycles, after which it is completely transformed into Cu2O and Cu. The high activity and selectivity of CuO were attributed to the facile formation of oxygen vacancies on the CuO surface under the reducing environment, as confirmed by X-ray photoelectron spectroscopy. Further, density functional theory simulations showed that oxygen vacancies led to higher adsorption (Eads = −174.4 kJ/mol) and selective activation of the nitro group (Ea = 43 kJ/mol) coupled with a reaction involving hydrogen atoms activated on the CuO surface. However, the presence of an additional pyridine ring in 5-nitroquinolines slightly impeded the rate of complete reduction (t = 10 min).

Insight into the precise catalytic mechanism of CuO on the decomposition and combustion of core–shell Al@AP particles

Burning rate modulation is a crucial but challenging technology for designing solid propellants. The core–shell structured Al@AP and Al@AP/CuO were prepared and their thermal reaction properties were investigated at different pressures. The precise catalytic mechanism of doped CuO in oxidizer and the key reason for its burning rate modulating effect on solid propellants were elucidated by combining DFT calculations. The *NH4ClO4 on the CuO (111) surface is more likely to undergo a dehydrogenation reaction first. The large difference in activation energy between *NH4ClO4→*NH3+*ClO4+*H and *NH4ClO4 → NH3 + HClO4 explains the reasons that CuO can reduce the ignition delay of the Al@AP. CuO promotes the decomposition of the AP@Al at the low- and high-temperature decomposition (LTD and HTD) stage. For the Al@AP-CuO, the temperature of the high-temperature decomposition peak (THTD) does not shift to the lower temperature range with increasing pressure. These results are responsible for a reduction of pressure exponent in the presence of minor CuO as reported in the literature. CuO can facilitate the transformation process *NH3→*NH2 on the CuO (111) surface at low-temperature and low-pressure conditions. However, at high-temperature and high-pressure conditions, it can inhibit the reaction *NH2→*NH→*N, so the burning rate of solid propellants can be controlled.

Catalytic Decomposition Mechanism of PH3 on 3DCuO/C and High Value Utilization of Deactivated Catalysts.

With the widespread application of lithium iron phosphatebatteries, the production capacity of the yellow phosphorus industry has increased sharply, and the treatment of the highly toxic by-product PH3 is facing severe challenges. In this study, a 3D copper-based catalyst (3DCuO/C) that can efficiently decompose PH3 at low temperatures and low oxygen concentrations is synthesized. The PH3 capacity is up to 181.41mgg-1 , which is superior to that previously reported in the literature. Further studies indicated that the special 3D structure of 3DCuO/C induces oxygen vacancies on the surface of CuO, which is beneficial to the activation of O2 , and then promotes the adsorption and dissociation of PH3 . The doping of P after dissociation determines the formation of Cu-P, and the eventual conversion to Cu3 P leads to the deactivation of CuO active sites. More strikingly, due to the appearance of Cu3 P, the deactivated De-3DCuO/C (Cu3 P/C) exhibited significant activity in the photocatalytic degradation of rhodamine B and photocatalytic oxidation of Hg0 (gas) and can also be a candidate as an anode material for Li batteries after modification, which will provide a more thorough and economical treatment scheme for deactivated catalysts.