Stability Of Cu Research Articles

Ozone-Assisted Cu-Based Catalysts for the Efficient Electro-Reforming Glycerol to Formic Acid.

Glycerol electrooxidation reaction (GOR) to produce value-added chemicals, such as formic acid, could make more efficient use of abundant glycerol and meet future demand for formic acid as a fuel for direct or indirect formic acid fuel cells. Non-noble metal Cu-based catalysts have great potential in electro-reforming glycerol to formic acid. However, the high activity, selectivity and stability of Cu based catalysts in GOR cannot be achieved simultaneously. Here, we used ozone-assisted electrocatalyst to convert glycerol to formic acid under alkaline conditions, the onset potential was reduced by 60 mV, the Faraday efficiency (FE) reached 95 %. The catalyst has excellent stability within 300 h at the current density of 10 mA cm-2. The electron spin resonance proved that ozone produced superoxide anion during the GOR. In situ Raman spectroscopy, electrochemical studies showed that glycerol can be activated with ozone in GOR, and the C-C bond can be broken to reduce the polymerization of glycerol on the catalyst surface, so as to produce more formic acid at a lower voltage. Moreover, the removal of dissolved O3 from water can be up to 100 % after 30 minutes of GOR reaction at a solubility of 50 mg L-1 as measured by UV-VIS spectrophotometry.

Boosting Fenton-like catalytic performance and environmental stability of nano zero-valent copper (nCu(0)) catalyst by inhibiting the formation of oxide layer: Catalytic performance and mechanistic study

Nano zero-valent copper (nCu(0)) as Fenton-like catalyst has shown great potential in the treatment of organic wastewater. However, nCu(0) is prone to be agglomerated and oxidated, causing to the reduction in catalytic ability. Herein, biochar supported highly dispersed nCu(0) (Cu/C) was synthesized by the carbonization method. And acid-modified strategy was proposed to inhibit the oxidation of nCu(0). Physicochemical properties of Cu/C catalysts modified by different acid (HCl, H2SO4 and HNO3) were analyzed by various characterizations. The results showed that only the introduction of HCl could obviously inhibit the formation of oxide layer on Cu(0), while HNO3 and H2SO4 couldn’t. Furthermore, the content of oxide layers decreased with the increase in HCl addition. Correspondingly, the catalytic performance enhanced gradually. Cu(0) was proved to be the active centers. And the presence of oxide layers was adverse to the catalytic reaction. When the adding amount of HCl reached to 1 mL, the Cu/C-HCl-1.0 catalyst showed the optimal catalytic performance. 97.1 % of p-nitrophenol (PNP) was degraded within 60 min. The reaction rate was 7.6 times that of unmodified Cu/C catalyst. Furthermore, Cu/C-HCl-1.0 catalyst possessed excellent environmental stability. After being directly exposed to air for 4 months, catalytic performance had no obvious decrease. In addition, the catalyst showed efficient degradation ability to phenols, dyes and antibiotics. And it was not sensitive to the initial pH of the organic solution (3.7 ∼ 11.2). OH was confirmed to be the main reactive species for the degradation of organic pollutants, which was formed by the decomposition of PMS by obtaining electrons from Cu(0). This work proposed a novel and efficient method to enhance the catalytic ability and environmental stability of Cu(0) by inhibiting the formation of oxide layer.

Melamine enhancing Cu-Fenton reaction for degradation of anthracyclines

Melamine (MA) enhanced Cu-Fenton process was developed for the degradation of anthracyclines. Taking daunorubicin (DNR) degradation as an example, we found that the initial first-order apparent constant of Cu2+/MA/H2O2 system with a molar ratio of 1:8 for Cu2+:MA was 5.2 times higher than that of conventional Cu2+/H2O2 system. The in-situ reductive coordination between Cu2+ and MA facilitated the generation and stabilization of Cu+ species, thereby accelerating the rate-limiting step of Cu2+/Cu+ conversion and maintaining high levels of Cu+ during the degradation process. Moreover, pre-synthesized Cu+-MA complexes (e.g., CM-250) further enhanced the efficiency of the Cu-Fenton reaction by increasing both the Cu+ proportion and MA chelation. The apparent activation energy for DNR degradation in CM-250 mediated Fenton reaction (15.9 kJ mol−1) was lower than that in systems involving Cu2+/MA (41.2 kJ mol−1) and Cu2+ (65.6 kJ mol−1). Enhanced generation of various reactive oxygen species (·OH,·O2-, and 1O2) was confirmed, with 1O2 playing a dominant role, significantly improving both degradation rate and mineralization degree for DNR. MA-enhanced Cu-Fenton process also offers a convenient alternative to effectively remove other anthracyclines and organic micropollutants, holding great promise for advancing advanced oxidation processes as well as practical large-scale degradation applications targeting multiple pollutants.

Boosting Photogenerated Electrons Transfer from FeVO4 to Peroxymonosulfate via Cu Doping for Stable Degradation of Organic Contaminants

Comprehensive SummaryElectron transfer is an important way to activate persulfate. Currently, the electrons for persulfate activation mainly originate from organic contaminants or the catalyst itself, which can lead to selective activation of persulfate or oxidation of the catalyst, respectively, and thus become a bottleneck restricting its application. In this work, Cu−doped FeVO4 (Cu−FVO) was prepared, and the results showed that Cu doping can significantly improve the photocatalytic activity and stability of FVO for peroxymonosulfate (PMS) activation. The optimized Cu−FVO/PMS/light system exhibited a high BPA degradation rate that is 4.3 times higher than that of the FVO/PMS/light. This system manifested a broad applicability to various organic contaminants even with complex matrix. Photoelectrochemical analysis and DFT theoretical calculations revealed that Cu doping boosted the photogenerated charge separation and the adsorption of PMS on FVO. Furthermore, Cu doping led to the establishment of an electron transfer channel from Cu−FVO to PMS, through which photogenerated electrons achieved an efficient PMS activation. Meanwhile, holes were consumed by organic contaminants to avoid the oxidation of catalyst. These collectively enhanced the photocatalytic activity and stability of Cu−FVO, which also maintained high catalytic activity even after 20 cycling degradation reactions.

Impact of H2 Reduction on the Performance and Stability of Phenol Catalytic Wet Air Oxidation (CWAO) Over Cu−Ce/AC Catalysts

AbstractIn this study, we utilized the carbon precursor derived from walnut shells to synthesize a series of Ce‐modified Cu‐based carbon catalysts (Cu−Ce/AC) via the impregnation method. We investigated the performance and stability of Cu−Ce/AC catalysts for CWAO phenol after H2 reduction at various temperatures. The Cu−Ce/AC‐250 catalyst exhibited its highest performance at 250 °C, achieving complete phenol conversion. Characterization results from techniques including XRD, BET, FTIR, ICP‐OES, SEM‐EDS, XPS, and H2‐TPR indicated that the active components of the H2‐reduced catalysts were more evenly distributed across the catalyst surface, thereby enhancing the availability of reactive sites for phenol oxidation. Simultaneously, under the appropriate temperature, the H2 atmosphere can reduce a portion of the Cu2+ on the catalyst surface to Cu+, thereby mitigating the loss of Cu components.

Effect of Y2O3 on high temperature thermal compression performance of Cu–10W composites and microstructure analysis

In this study, Cu–10W and 2 wt%Y2O3/Cu–10W composites were successfully prepared via mechanical ball milling and spark plasma sintering. Hot compression experiments on the two materials were carried out in the temperature range of 300°C-600 °C and in the strain rate range of 0.01 s−1–10 s−1. The hot deformation activation energy of the two materials was calculated and a constitutive equation was established. The optimum hot deformation process parameters were obtained according to a hot processing map. The effects of Y2O3 on the thermal deformation behavior of the Cu–10W composites and their microstructures were investigated, and the results showed that Y2O3 could enhance the stability of Cu–10W at high temperatures. The activation energies of thermal deformation of Cu–10W and 2 wt%Y2O3/Cu–10W were 159.56 kJ/mol and 129.85 kJ/mol, respectively. Moreover, Y2O3 improved the interfacial bonding strength of Cu and W in the Cu–10W material, effectively preventing the generation of microcracks and pores during the high-temperature compression process; Y2O3 provides more nucleation sites in the recrystallization process, which is favorable for the excitation of recrystallization. A low strain rate at high temperatures favors the occurrence of recrystallization, and the 2 wt%Y2O3/Cu–10W composites tend to exhibit discontinuous dynamic recrystallization (DDRX) under high-Z-value conditions and continuous dynamic recrystallization (CDRX) under low-Z-value conditions.

High acidity organic waste degradation and the potential to bioremediation of heavy metals in soil by an acid-tolerant Serratia sp.

Highly acidic citrus pomace (CP) is a byproduct of Pericarpium Citri Reticulatae production and causes significant environmental damage. In this study, a newly isolated acid-tolerant strain of Serratia sp. JS-043 was used to treat CP and evaluate the effect of reduced acid citrus pomace (RACP) in passivating heavy metals. The results showed that biological treatment could remove 97.56% of citric acid in CP, the organic matter in the soil increased by 202.60% and the catalase activity in the soil increased from 0 to 0.117Ug-1. Adding RACP into soil can increase the stabilization of Cu, Zn, As, Co, and Pb. Specifically, through the metabolism of strain JS-043, RACP was also involved in the stabilization of Zn and Pb, and Residual Fraction in the total pool of these metals increased by 10.73% and 10.54%, respectively. Finally, the genome sequence of Serratia sp. JS-043 was completed, and the genetic basis of its acid-resistant and acid-reducing characteristics was preliminarily revealed. JS-043 also contains many genes encoding proteins associated with heavy metal ion tolerance and transport. These findings suggest that JS-043 may be a high-potential strain to improve the quality of acidic organic wastes that can then be useful for soil bioremediation.

Interrogation of Oxidative Pulsed Methods for the Stabilization of Copper Electrodes for CO2 Electrolysis.

Using copper (Cu) as an electrocatalyst uniquely produces multicarbon products (C2+-products) during the CO2 reduction reaction (CO2RR). However, the CO2RR stability of Cu is presently 3 orders of magnitude shorter than required for commercial operation. One means of substantially increasing Cu catalyst lifetimes is through periodic oxidative processes, such as cathodic-anodic pulsing. Despite 100-fold improvements, these oxidative methods only delay, but do not circumvent, degradation. Here, we provide an interrogation of chemical and electrochemical Cu oxidative processes to identify the mechanistic processes leading to stable CO2RR through electrochemical and in situ Raman spectroscopy measurements. We first examine chemical oxidation using an open-circuit potential (OCP), identifying that copper oxidation is regulated by the transient behavior of the OCP curve and limited by the rate of the oxygen reduction reaction (ORR). Increasing O2 flux to the cathode subsequently increased ORR rates, both extending lifetimes and reducing "off" times by 3-fold. In a separate approach, the formation of Cu2O is achieved through electrochemical oxidation. Here, we establish the minimum electrode potentials required for fast Cu oxidation (-0.28 V vs Ag/AgCl, 1 M KHCO3) by accounting for transient local pH changes and tracking oxidation charge transfer. Lastly, we performed a stability test resulting in a 20-fold increase in stable ethylene production versus the continuous case, finding that spatial copper migration is slowed but not mitigated by oxidative pulsing approaches alone.

Enhancing CO2 Electroreduction Performance through Si-Doped CuO: Stabilization of Cu+/Cu0 Sites and Improved C2 Product Selectivity

Enhancing CO₂ Electroreduction Performance through Si-Doped CuO: Stabilization of Cu⁺/Cu⁰ Sites and Improved C₂ Product Selectivity

Stable, while Still Active? A DFT Study of Cu, Ag, and Au Single Atoms at the C3N4/TiO2 Interface.

Hybrid DFT calculations are employed to compare the adsorption and stabilization of Cu, Ag, and Au atoms on graphitic C3N4 and on the heterojunction formed by g- C3N4 and TiO2. While Cu and Ag can be strongly chemisorbed in form of cations on g- C3N4, Au is only weakly physisorbed. On g- C3N4/TiO2, all coinage metal adatoms can be strongly chemisorbed, but, while Cu and Ag forms cations, Au form an Au- species. Ab Initio Molecular Dynamics simulations confirm that the metal adatoms on g-C3N4 are highly mobile at room temperature, while they remain confined in the interfacial spacing between C3N4 and TiO2 on the heterojunction, being both stably bound and reachable for the reactants in a catalytic cycle. Doping g- C3N4/TiO2 with metal single atoms permits thus to generate catalytic systems with tunable charge and chemical properties and improved stability with respect to bare C3N4. Moreover, the changes in the electronic structure of g- C3N4/TiO2 induced by the presence of the metal single atoms are beneficial also for photocatalytic applications.

Remediation effect of walnut shell biochar on Cu and Pb co-contaminated soils in different utilization types

Biochar, with its dual roles of soil remediation and carbon sequestration, is gradually demonstrating great potential for sustainability in agricultural and ecological aspects. In this study, a porous biochar derived from walnut shell wastes was prepared via a facile pyrolysis coupling with in-situ alkali etching method. An incubation study was conducted to investigate its performance in stabilizing copper (Cu) and lead (Pb) co-contaminated soils under different utilization types. The biochar effectively decreased the bioavailable Cu (8.5–91.68%) and Pb (5.03–88.54%), while increasing the pH, CEC, and SOM contents in both soils. Additionally, the results of sequential extraction confirmed that biochar promoted the transformation of the labile fraction of Cu and Pb to stable fractions. The mechanisms of Cu and Pb stabilization were found to be greatly dependent on the soil types. For tea plantation yellow soil, the main approach for stabilization was the complexation of heavy metals with abundant organic functional groups and deprotonation structure. Surface electrostatic adsorption and cation exchange contributed to the immobilization of Cu and Pb in vegetable-cultivated purple soil. This research provides valuable information for the stabilization of Cu and Pb co-contaminated soils for different utilization types using environmentally-friendly biochar.

Cu single atoms mediated multiple active site reconfiguration to trigger Dual-pathway nonradical peroxymonosulfate activation process

Developing atomically dispersed metal sites is vital to enhance the activation of peroxymonosulfate (PMS). However, for catalyst systems where single atoms and nanoclusters coexist, how to identify the independent and synergistic effects of atomic sites and investigate the possible coexistence of multiple activation mechanisms still remains a great challenge. Herein, CuSA/CoOx-CeO2 catalysts with Cu single atoms and CoOx nanoclusters were fabricated for PMS activation. The introduction of Cu single atoms led to the reconstruction and diversification of catalytic active sites of CoOx-CeO2. The synergy between CoOx nanoclusters and neighboring Cu single atoms in CuSA/CoOx-CeO2 catalyst led to the 1O2 pathway of PMS activation, while the isolated Cu atom induced the Cu(III) oxidation pathway. The introducing of adjacent Cu single atoms caused the redistribution of the site charges in CoOx nanoclusters, which enhanced the charge transfer and promoted the adsorption and activation behavior of PMS molecules. During the evolution of 1O2, the synergistic effect of Cu single atoms and CoOx nanoclusters increased the stability of the reaction intermediate state (*OO*SO3), reducing the total Gibbs free energy change (ΔG) required for 1O2 formation. Compared with the cooperative site, the isolated Cu-O4 sites exhibited stronger charge transfer capacity to PMS molecules and were more conducive to the activation of the local substrate electronic structure, facilitating the formation and stabilization of Cu(III)–OH metastable intermediates. Overall, this study demonstrated the importance about the construction of multi-site induced multipath coexisting PMS activation system and the accurate identification of active sites.

Outstanding shape memory effect and thermal stability of Cu–Al–Ni-based high temperature shape memory alloys achieved by Gd and Mn doping

In this paper, the effects of Mn element and rare earth element Gd on the microstructure, thermal stability, mechanical properties and shape memory effect of polycrystalline Cu-12.0Al-4.0Ni and Cu-12.0Al-4.0Ni-1.5Mn-xGd high-temperature shape memory alloy were investigated. The results show that the Cu-12.0Al-4.0Ni alloy exhibits millimeter-sized grain, dual-phase structure with coexistence of 18R and 2H martensite and poor thermal stability. When the Mn and Gd element was added to Cu-12.0Al-4.0Ni alloys, the grain size can be refined by an order of magnitude, and the 2H martensite disappeared completely, accompanied by the formation of the AlCu4Gd phase, meanwhile, thermal stability is significantly improved. The grain refinement improves the mechanical properties and shape memory effect of Cu-12.0Al-4.0Ni-1.5Mn-xGd alloys. When x = 0.3, the compressive fracture stress, compressive fracture strain and recoverable strain can reach 969 MPa, 15 % and 8 %, respectively.

Cu/Zn bimetallic catalysts prepared by facial potential steps electrodeposition favoring Zn deposition and grain boundary formation for efficient CO2ER to ethylene

Electro-reduction of CO2 (CO2ER) is a promising way to reduce atmospheric CO2 meanwhile gaining high-value-added products (e.g. ethylene). Introducing zinc, a kind of cheap, non-hazardous metal into copper, can perform tandem catalytic functions to overcome the disadvantage of pure Cu. However, due to the quite different theoretical reduction potentials of Cu2+ and Zn2+, Cu/Zn bimetallic catalysts are difficult to be synthesized using the electrochemical method. Here, a facial Potential Steps electrodeposition (PSE) method was proposed to prepare Cu/Zn bimetal catalyst supported on a gas diffusion layer (CuZn/GDE), during which, a lower voltage only suitable for Cu’s deposition was firstly applied, and then a higher voltage was imposed. Worthy mentioned, during the first step, Zn2+ could also transfer to the cathode from the bulk solution and then be embedded by the deposited Cu, forming a capsule-analogous micro-reaction environment composed of highly electron-conductive Cu and enriched Zn2+, thus decreasing the over-potential of Zn’s deposition, further promoting the reduction of Zn & the formation of Cu/Zn grain boundary and the stabilization of Cu(I) in the second step. The optimized CuZn/GDE could achieve a high faradaic efficiency to ethylene (40.2 %) at −1.36 V vs RHE in H-cell. The DFT calculations showed that the *CO formation energy at Cu/Zn and Cu(0)/Cu(I) was lower than at pure Cu and that the formation of *COCOH at Cu(0)/Cu(I) was more thermodynamically favorable than at pure Cu. This work supplies a facial and effective strategy to synthesize copper-based bimetallic catalysts for CO2ER, which could decrease the over-potential of the metal with high deposition potential, and meanwhile form grain boundary, in favor of generation of C2 products.

Asymmetric Cu(I)─W Dual-Atomic Sites Enable C─C Coupling for Selective Photocatalytic CO2 Reduction to C2H4.

Solar-driven CO2 reduction into value-added C2+ chemical fuels, such as C2H4, is promising in meeting the carbon-neutral future, yet the performance is usually hindered by the high energy barrier of the C─C coupling process. Here, an efficient and stabilized Cu(I) single atoms-modified W18O49 nanowires (Cu1/W18O49) photocatalyst with asymmetric Cu─W dual sites is reported for selective photocatalytic CO2 reduction to C2H4. The interconversion between W(V) and W(VI) in W18O49 ensures the stability of Cu(I) during the photocatalytic process. Under light irradiation, the optimal Cu1/W18O49 (3.6-Cu1/W18O49) catalyst exhibits concurrent high activity and selectivity toward C2H4 production, reaching a corresponding yield rate of 4.9µmol g-1 h-1 and selectivity as high as 72.8%, respectively. Combined in situ spectroscopies and computational calculations reveal that Cu(I) single atoms stabilize the *CO intermediate, and the asymmetric Cu─W dual sites effectively reduce the energy barrier for the C─C coupling of two neighboring CO intermediates, enabling the highly selective C2H4 generation from CO2 photoreduction. This work demonstrates leveraging stabilized atomically-dispersed Cu(I) in asymmetric dual-sites for selective CO2-to-C2H4 conversion and can provide new insight into photocatalytic CO2 reduction to other targeted C2+ products through rational construction of active sites for C─C coupling.

Highly stable Cu catalyst embedded in N-doped carbon microsphere for hydrogenation of dimethyl oxalate to methyl glycolate

Cu catalyst often subjects to low stability due to chemical state transformation during carbon-oxygen hydrogenation reaction. In the present work, the copper catalysts embedded in N-doped carbon microsphere (Cu@NC) were fabricated by one-pot hydrothermal method and applied in dimethyl oxalate (DMO) hydrogenation to methyl glycolate (MG). The optimized Cu@10NC catalyst exhibited an excellent stability with DMO conversion of 80.1% and MG selectivity of 80.3% during 220 h long-term evaluation under 1.9 MPa, 210 °C, H2/DMO molar ratio of 80 and WHSV of 0.8 gDMO·gCu−1·h−1, beneficial from the stable Cu+ ratio and confinement effect of carbon support during the reaction. The Cu dispersion and Cu+ proportion can be finely controlled by varying the N-doping content due to the enhanced interaction between Cu and carbon microspheres. Particularly, graphitic-N is primarily accountable for Cu dispersion, while pyridinic-N is dominantly responsible for the stabilization of Cu+ species.

Effect of Hf addition on structural transformation and aging stability of Cu–15Ni–8Sn alloy

The Cu–15Ni–8Sn-xHf (wt.%, x = 0–0.6) alloys were prepared by vacuum melting, and the effect of Hf on the micro-structure of as-cast, as-solution-treated and as-aged alloys was systematically investigated, as well as the alloy aging stability. The Hf addition provided a significant role on refining the solidification structure and reducing the micro-segregation degree, and it also made γ-D03 phases more likely to form in needlelike-shape rather than lamellar-shape. With the presence of more Hf atoms, their existence form was accordingly changed from solid solute atoms to nano-scale precipitation phases and then to micron-scale segregation phase. A small content of Hf (0.1 wt%) could effectively improve the aging stability by inhibiting the growth of γ-D03. Once its content reached or exceeded 0.3 wt%, the harmful discontinuous precipitation was completely inhibited, and the common lamellar-shape γ-D03 locating around the grain boundary was no longer formed. Even the alloy failed at higher temperatures, it could only be carried out through the continuous precipitation method, namely the generation of needlelike-shape γ-D03 uniformly in the matrix. The appropriate Hf addition was capable of extending the alloy aging window, and the hardness of Cu–15Ni–8Sn-0.3Hf alloy could still exceed 360 HV even after 48 h aging.

Synthesis of hydrophobic CuCl/LaA modified by butyltrichlorosilane towards enhanced CO adsorption under humid environment

Cuprous ion modified molecular sieves have been considered as promising CO adsorbents in gas separation or purification industry. However, it persists as a significant challenge to overcome the unfavorable effect of water vapor in the work environment on gas adsorption and separation. Herein, we propose a synthetic strategy using rare earth element La as an additive to form LaOLa coordination bonds followed by surface silanization treatment to construct a hydrophobic SiOSi barrier to significantly improve the stability of Cu+ under humid atmosphere. By successively introducing La3+ and Cu+ into zeolite 5A, CuCl/LaA adsorbents were prepared via ion exchange and solid dispersion methods. And then by silanization modification using toluene as solvent and butyltrichlorosilane (BTS) as hydrophobic agent, hydrophobic CuCl/LaA-BTS adsorbents were prepared. Dynamic adsorption investigation demonstrated that the as-prepared CuCl/LaA-BTS adsorbents possessed hydrophobic surface and consequently the adsorption capacity of CO was enhanced significantly under humid atmosphere. The CO adsorption breakthrough capacity over CuCl/LaA-BTS attained 0.34 mg/g, which was 5.7 times higher than that of zeolite 5A at 40 °C, atmospheric pressure and a relative humidity of RH = 55 %. Moreover, the CO adsorption capacity of CuCl/LaA-BTS retained 0.31 mg/g after four cycle regenerations. This work provides an effective and novel route for synthesizing highly stable cuprous ion modified zeolite adsorbents.

Effect of Al2O3 coating thickness on the thermal stability of Cu–carbon nanotube hybrids

Effect of Al2O3 coating thickness on the thermal stability of Cu–carbon nanotube hybrids

Cu2O/LDH heterojunction derived from CuMgAl-LDH: Enhanced stability of Cu+ in CO2 electroreduction

The unique ability of Cu+ to enhance C-C coupling makes it important in the field of CO2 reduction reaction (CO2RR) over Cu-based catalyst, while Cu+ is very prone to deactivation. Hereby, we propose a simple and feasible stabilization strategy to stabilize Cu+ species through reducing Cu-Mg-Al hydrotalcite by adding ascorbic acid, which owns stable product selectivity in a span of 6 h at −0.95 V vs.RHE. Characterization results show that the excellent stability is promoted by the heterostructure of Cu2O and hydrotalcite with retained Cu+ species, which derives from Cu2O and slow down the rapid reduction of Cu+ to Cu0.