State Of Cu Research Articles

Genomic characterization of a novel ureolytic bacteria, Lysinibacillus capsici TSBLM, and its application to the remediation of acidic heavy metal-contaminated soil

Soil heavy metal contamination is an essential challenge in ecological and environmental management, especially for acidic soils. Microbially induced carbonate precipitation (MICP) is an effective and environmentally friendly remediation technology for heavy metal contaminated sites, and one of the key factors for its realization lies in the microorganisms. In this study, Lysinibacillus capsici TSBLM was isolated from heavy metal contaminated soil around a gold mine, and inferred to be a novel ureolytic bacteria after phylogenomic inference and genome characterization. The urease of L. capsici TSBLM was analyzed by genetic analysis and molecular docking, and further applied this bacteria to the remediation of Cu and Pb in solution and acidic soils to investigate its biomineralization mechanism and practical application. The results revealed L. capsici TSBLM possessed a comprehensive urease gene cluster ureABCEFGD, and the encoded urease docked with urea at the lowest binding energy site (ΔG = −3.43 kcal/mol) connected to three amino acids threonine, aspartic, and alanine. The urease of L. capsici TSBLM is synthesized intracellularly but mainly functions extracellularly. L. capsici TSBLM removes Cu/Pb from the solution by generating heavy metal carbonates or co-precipitating with CaCO3 vaterite. For acidic heavy metal-contaminated soil, the carbonate-bound states of Cu and Pb increased significantly from 7 % to 16 % and from 23 % to 35 % after 30 days by L. capsici TSBLM. Soil pH improved additionally. L. capsici TSBLM maintained the dominant status in the remediated soil after 30 days, demonstrating good environmental adaptability and curing persistence. The results provided new strain resources and practical application references for the remediation of acidic heavy metal contaminated soil based on MICP.

Electrocatalytic Nitrate and Nitrite Reduction toward Ammonia Using Cu2O Nanocubes: Active Species and Reaction Mechanisms.

The electrochemical reduction of nitrate (NO3-) and nitrite (NO2-) enables sustainable, carbon-neutral, and decentralized routes to produce ammonia (NH3). Copper-based materials are promising electrocatalysts for NOx- conversion to NH3. However, the underlying reaction mechanisms and the role of different Cu species during the catalytic process are still poorly understood. Herein, by combining quasi in situ X-ray photoelectron spectroscopy (XPS) and operando X-ray absorption spectroscopy (XAS), we unveiled that Cu is mostly in metallic form during the highly selective reduction of NO3-/NO2- to NH3. On the contrary, Cu(I) species are predominant in a potential region where the two-electron reduction of NO3- to NO2- is the major reaction. Electrokinetic analysis and in situ Raman spectroscopy was also used to propose possible steps and intermediates leading to NO2- and NH3, respectively. This work establishes a correlation between the catalytic performance and the dynamic changes of the chemical state of Cu, and provides crucial mechanistic insights into the pathways for NO3-/NO2- electrocatalytic reduction.

Oxidation state of Cu in silicate melts at upper mantle conditions

Beyond its economic value, copper (Cu) serves as a valuable tracer of deep magmatic processes due to its close relationship with magmatic sulfide evolution and sensitivity to oxygen fugacity (fO2). However, determining Cu’s oxidation state (+ 1 or + 2) in silicate melts, crucial for interpreting its behavior and reconstructing fO2 in the Earth’s interior, has long been a challenge. This study utilizes X-ray Absorption Near Edge Structure spectroscopy to investigate the Cu oxidation state in hydrous mafic silicate melts equilibrated under diverse fO2 (− 1.8 to 3.1 log units relative to the Fayalite–Magnetite–Quartz buffer), temperature (1150–1300 °C), and pressure (1.0–2.5 GPa) conditions. Our results reveal that Cu predominantly exists as Cu+ across all fO2 conditions, with a minor Cu2+ component. This dominance of Cu+ persists even in relatively oxidized melts, highlighting its limited sensitivity to fO2 under upper mantle conditions. This significantly constrains the utility of Cu as an oxybarometer in hydrous silicate melts in the deep Earth. However, our findings suggest that Cu isotopes primarily reflect the interplay of sulfide segregation/accumulation during magmatic differentiation, shedding light on these fundamental processes in Earth’s interior.

Cu(I/II)-Co(II/III) photocatalyst with intrinsic electron transport centre for photoreduction of chromium(VI) and photodegradation of methyl violet

A redox switchable photocatalyst consisting of mixed valent copper (CuI/II) sulfide (CuxS) and cobalt (CoII/III) oxide (CoyOz) designated as CuxS-CoyOz (x=1,2, y=1,3 and z=1,4) was synthesized to execute the Z-scheme photocatalysis process for photoreduction of chromium(VI), and photodegradation of Methyl Violet (MV) dye. The synthesized photocatalyst with a band gap of 3.3 eV was found to be highly effective to reduce 99.62% Cr(VI) and 99.32% of MV dye under UV-light irradiation. The possibility of switching the oxidation state in Cu and Co centre favored the band edge electron transfer on light irradiation and supported the Z-scheme electron transport chain. The photocatalytic reduction and degradation process was dependent on various reaction conditions like catalyst amount, pH of the reaction mixture, irradiation time. The reduction of Cr(VI) occurred with high efficacy at pH=2 while the MV dye degradation proceeded at high pH=10. The catalyst could reduce maximum concentration of Cr(VI) upto 250 ppm and MV dye upto 10−3 M. The mechanism of the photocatalytic processes were well studied by different spectroscopic and electrochemical analysis. The photocatalytic activity of synthesized CuxS-CoyOz catalyst was compared with five other transition metal sulfides M-S (MnS, FeS, CoaSb, NiS and ZnS, where a=3, 4; b=3, 4) combined with cobalt oxide and it was found that CuxS-CoyOz exhibited the highest activity in both the photocatalytic process.

Phenolic Ligand-Metal Charge Transfer Induced Copper Nanozyme with Reactive Oxygen Species-Scavenging Ability for Chronic Wound Healing.

Chronic wounds frequently arise as a complication in diabetic patients, and their management remains a significant clinical hurdle due to their nonhealing nature featured by heightened oxidative stress and impaired healing cells at the wound site. Herein, we present a 2D copper antioxidant nanozyme induced by phenolic ligand-metal charge transfer (LMCT) to eliminate reactive oxygen species (ROS) and facilitate the healing of chronic diabetic wounds. We found that polyphenol ligands coordinated on the Cu3(PO4)2 nanosheets led to a strong charge transfer at the interface and regulated the valence states of Cu. The obtained Cu nanozyme exhibited efficient scavenging ability toward different oxidative species and protected human cells from oxidative damage. The nanozyme enhanced the healing of diabetic wounds by promoting re-epithelialization, collagen deposition, angiogenesis, and immunoregulation. This work demonstrates the LMCT-induced ROS scavenging ability on a nanointerface, providing an alternative strategy of constructing metal-based nanozymes for the treatment of diabetic wounds as well as other diseases.

Strategies to Modulate the Copper Oxidation State Toward Selective C2+ Production in the Electrochemical CO2 Reduction Reaction.

The electrochemical reduction of CO2 to form value-added chemicals receives considerable attention in recent years. Copper (Cu) is recognized as the only element capable of electro-reducing CO2 into hydrocarbons with two or more carbon atoms (C2+), but the low product selectivity of the Cu-based catalyst remains a major technological challenge to overcome. Therefore, identification of the structural features of Cu-based catalysts is of great importance for the highly selective production of C2+ products (ethylene, ethanol, n-propanol, etc.), and the oxidation state of Cu species in the catalysts is found critical to the catalyst performance. This review introduces recent efforts to fine-tune the oxidation state of Cu to increase carbon capture and produce specific C2+ compounds, with the intention of greatly expediting the advance in the catalyst designs. It also points to the remaining challenges and fruitful research directions for the development of Cu-based catalysts that can shape the practical CO2 reduction technology.

CuAs2O4: Design, Hydrothermal Synthesis, Crystal Structure, Photocatalytic Dye Degradation, Hydrogen Evolution Reaction, Knoevenagel Condensation Reaction, and Thermal Studies.

CuAs2O4 has been explored as a heterogeneous catalyst in the fields of photocatalysis, electrocatalysis, and solvent-free organic transformation reactions. The homogeneity has been successfully attained for the first time by designing a pH-assisted hydrothermal synthesis technique. Single-crystal X-ray diffraction studies reveal that no phase transition has been observed by lowering the temperature up to 103 K with no existence of satellite reflections. The crystal structure exhibits tetragonal symmetry with space group P42/mbc and consists of [CuO6] octahedra and [AsO3E] tetrahedra (E represents the stereochemically active lone pair). Structural investigation shows a cylindrical void inside the structure, which could lead to interesting physical and chemical properties. The photocatalytic dye degradation efficiency with methylene blue (MB) showed ∼100% degradation, though the degradation efficiency increased by 2-fold with the addition of 6% H2O2. The reusability of the catalyst up to the 10th cycle with ∼35% MB dye degradation has been established. It can exhibit HER activity with a low overpotential of 165 mV with respect to RHE to attain the current density of j = 10 mA cm-2. SEM and TEM revealed rod-shaped particles, which supported the large number of catalytic active sites. The structural consistency of the catalyst after photodegradation and HER studies is confirmed by the PXRD pattern. XPS confirms the oxidation state of Cu and As in the compound. The catalytic activity toward the Knoevenagel condensation reaction at moderate temperature under solvent-free condition is also studied. TG-DTA shows an endothermic minimum (Tmin) at 436 °C due to the mass loss of As2O3.

Origin of microscopically coupled ferromagnetic Cu-ions in a distorted system of Cu-doped ZnO and their synchrotron-based electronic structures

Spintronics-based studies have produced significant attention in the last decade while claiming the observation of room temperature ferromagnetism (RTFM). Nevertheless, there is a lack of consensus on a mechanism responsible for this phenomenon. In this study, we focus on Cu-doped ZnO (ZCO) to understand the microscopic origin of RTFM and the role of different oxidation states of Cu in RTFM. We have performed different spectroscopic techniques using synchrotron facilities. The values of spin-moment obtained from x-ray magnetic circular dichroism sum-rule truly exhibit a ferromagnetic interaction in the nanocrystalline powder of ZCO with ∼0.58 μB for 5% of Cu concentration in the total fluorescence yield mode. Such an enhanced magnetization is attributed to the presence of Cu2+, which is mainly localized in the bulk region. Cu in ZCO is mostly dominated by the presence of Cu2+. This is clearly reflected by the profiles of x-ray photoemission spectroscopy. Consequently, the weakly magnetized total electron yield mode is attributed to a state of magnetic frustration as the majority of Cu3+ is found on the surface. Some of these Cu3+ when come in the vicinity of Cu2+ ions result in a highly correlated state of double exchange mechanism, which is the microscopic origin of RTFM in ZCO. The coupling between Cu2+-Cu3+ is mediated via oxygen vacancies (VO), the presence of which is confirmed through the features of electron energy loss spectroscopy over different edges. The confirmation of VO is also supported by the deconvolution of E2high-phonon in the Raman spectra. Moreover, the defects in the local electronic structures of ZCO are demonstrated by the deconvoluted spectra of Cu L3 x-ray absorption spectroscopy. The images obtained from high-resolution transmission electron microscopy confirm the incorporation of Cu into the wurtzite crystal of ZnO. A clear enhancement in magnetization upon an increase in carriers of Cu in ZCO indicates carrier-induced ferromagnetism. Cu2+ and VO are the two attributes of RTFM in ZCO.

Dual mechanisms in hydrogen reduction of copper oxide: surface reaction and subsurface oxygen atom transfer.

The study of the reduction of copper oxide (CuO) by hydrogen (H2) is helpful in elucidating the reduction mechanism of oxygen carriers. In this study, the reduction mechanism of CuO by H2 and the process of oxygen atom transfer were investigated through the density functional theory (DFT) method and thermodynamic calculation. DFT calculation results showed that during the reaction between H2 and the surface of CuO, Cu underwent a Cu2+ → Cu1+ → Cu0 transformation, the Cu-O bond (-IpCOHP = 2.41) of the Cu2O phase was more stable than that (-IpCOHP = 1.94) of the CuO phase, and the reduction of Cu2O by H2 was more difficult than the reduction of CuO. As the surface oxygen vacancy concentration increased, it was more likely that the subsurface O atoms transfer to the surface at zero H2 coverage (no H2 molecule on the surface), allowing the surface to maintain a stable Cu2O phase. However, when the H2 coverage was 0.25 monolayer (ML) (one H2 molecule every four surface Cu atoms), the presence of H atoms on the surface made the upward transfer of O atoms from the subsurface more difficult. The rate of consuming surface O atoms in the reduction reaction was greater than the rate of subsurface O atom transfer induced by the reduction reaction and the surface Cu2O phase could not be maintained stably. Through thermodynamic analysis, at high H2 concentration, the reaction between H2 and CuO was more likely to generate Cu, while at low H2 concentration, it was more likely to generate Cu2O. In summary, the valence state of Cu in the reaction process between CuO and H2 depended on the concentration of H2.

Biomineralization mechanism and remediation of Cu, Pb and Zn by indigenous ureolytic bacteria B. intermedia TSBOI

Microbially induced carbonate precipitation (MICP) is an effective and eco-friendly technology for remediating heavy metal-contaminated sites. In this study, we investigated the response discrepancies and proposed the dominant removal mechanism of the ureolytic bacteria Brucella intermedia TSBOI for different heavy metal species (Cu, Pb and Zn) under concentration gradients (0.1, 0.2, 0.4, 0.8, and 1.6 mmol/L), and explored the remediation of soil heavy metal pollution by B. intermedia TSBOI under laboratory conditions. The results showed that the heavy metal concentration significantly affected the bacterial cell concentration, urease activity, cell morphology, surface functional groups, and removal efficiency of B. intermedia TSBOI. The presence of Ca2+ negatively affected the biomass and urease activity to some extent but had a non-negligible positive effect of removing heavy metals and was more conducive to the formation and precipitation of biomineralization products. The ability of B. intermedia TSBOI to produce urease intracellularly and secrete it in large quantities to act extracellularly is key to the sustained immobilization of heavy metals and the outstanding performance of B. intermedia TSBOI bacterial solution. The results of heavy metal-contaminated soil remediation showed that B. intermedia TSBOI effectively increased the proportion of carbonate-bound states of Cu, Pb and Zn in the soil and reduced the bioavailability of heavy metals within 30 days. B. intermedia TSBOI could adapt fully to the soil environment and became a dominant genus.

Efficient electrochemical reduction of CO2 to CO in a flow cell device by a pristine Cu5tz6-cluster-based metal-organic framework.

The electrochemical reduction of CO2 to CO is a powerful approach to achieving carbon neutrality. Herein, we report a five-nuclear copper cluster-based metal-azolate framework CuTz-1 as an electrocatalyst for the electrochemical CO2 reduction reaction. It achieved a faradaic efficiency (FE) of 62.7% for yielding CO with a partial current density of -35.1 mA cm-2 in flow cell device, which can be preserved for more than ten hours with negligible changes of the current density and FE(CO). Studies of electrocatalytic mechanism studies revealed that the distance of Cu-N was increased, and the coordination number of the Cu ion was reduced, while the oxidation state of Cu was decreased after the electrocatalysis. These findings offer valuable insights into structural changes that influence the performance of the catalyst during the process of the electrochemical reduction of CO2 process.

Effect of Y3+ doping of rare earth element on microstructure and antiferromagnetism of CuFeO2 ceramics

In this work, a set of CuFe1-xYxO2 (x = 0–0.02) specimens were synthesized using the conventional high-temperature solid-state reaction method, and the impact of Y3+ doping on the microstructure and magnetic properties of CuFeO2 ceramics was investigated. The introduction of Y3+ ions in place of Fe3+ ions induced alterations in the microstructure of CuFeO2, leading to lattice distortion. X-ray diffraction analysis confirmed the presence of impurity phases in the CuFe1-xYxO2 series samples at high doping concentrations (x ≥ 0.015). In contrast, low doping concentrations (x ≤ 0.0125) exhibited a singular copper-iron ore structure. The microstructures of the ceramic samples were examined using SEM, findings suggest that the presence of high concentrations of dopants hinders the formation of ceramic samples with high density. XPS analysis reveals that the introduction of a low concentration of Y3+ dopant does not impact the oxidation state of Cu and Fe. Raman spectroscopy results indicate that the doping process weakens the vibration mode of CuFe1-xYxO2 ceramic samples. Additionally, measurements conducted using the PPMS demonstrate that the serial samples undergo two consecutive magnetic phase transitions at temperatures of 16K and 11K. The magnetization versus M − H curve of the doped sample exhibits both antiferromagnetic and ferromagnetic behavior. The increase in magnetic susceptibility can be attributed to the greater magnetic moment of doped Y3+ compared to Fe3+. Consequently, the magnetic transformation of the sample is influenced by various factors, including lattice distortion, alterations in ion valence states, variations in microscopic defect types, and modifications in magnetic interactions.

Preventing Pt Catalysts in PEM Fuel Cells from CO Poisoning by Getting COPROX to Work

Proton-exchange membrane fuel cells still require CO-scrubbed H2 feedstreams to sustain long-duration performance. Sufficiently CO-free H2 costs an order of magnitude more than steam refining fossil fuels to generate H2—and until green processes produce the bulk of H2, preferential oxidation of CO from H2-rich feedstreams, also known as COPROX, is a necessity. We design architected catalytic platforms as ultraporous metal nanoparticle–modified oxide aerogels in which a covalently bonded oxide nanoparticulate network (NPs) supports comparably sized catalytic nanoparticles (NPs). The degree of physical and chemical interfacial intimacy stabilizes the more catalytically active low valent state of Cu and the ultraporous catalytic platform demonstrates high activity and on-stream durability for thermal catalysis of CO [1]. We then evaluate the selectivity and activity of this architected catalyst and a related aerogel, Cu/GdxCe1–xO2, for preferential oxidation of CO (COPROX) in H2 feedstreams. The catalysts convert >95% of CO at temperatures that prevent oxidation (consumption) of the H2 fuel (a purification reaction necessary to prevent poisoning of the anode catalysts in H2 fuel cells). The architected Cu/ceria catalysts achieve >95% selectivity vs. H2 and maintain this unprecedented activity for >16 h at 100°C in dry or humidified feedstreams [2,3]. The ability to purify H2 from steam-reformed fuels for use in proton-exchange membrane fuel cells increases power source flexibility as the world transitions to more sustainable, carbon-neutral routes to highly purified H2.[1] Stabilization of reduced copper on ceria aerogels for CO oxidation. C. L. Pitman, A. M. Pennington, T. H. Brintlinger, D. E. Barlow, L. F. Esparraguera, R. M. Stroud, J. J. Pietron, P. A. DeSario, D. R. Rolison, Nanoscale Adv. 2020, 2, 4547–4556 (10.1039/D0NA00594K).[2] Preferential oxidation of CO in H2-containing gas. T.G. Novak, D.R. Rolison, P.A. DeSario, US Patent Application, filed Jan 27, 2023 [Navy Case #210,945].[3] Cu/CeO2 and Cu/Gd-substituted CeO2 aerogels for active, selective, and stable COPROX catalysis. T.G. Novak, P.A. DeSario, T.H. Brintlinger, R.H. DeBlock, J.W. Long, and D.R. Rolison, ACS Sus. Chem. Eng. 2023, 11, 2853–2860 (10.1021/acssuschemeng.2c06158).

Ce enhanced low-temperature performance of Mn modified Cu-Beta zeolite catalyst for NH3-SCR

The zeolite-based catalyst is a promising option for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) due to its low toxicity. However, the challenge lies in its low-temperature activity. This study developed a multi-component catalytic system consisting of Ce/Mn/Cu-loaded Beta zeolite to reduce NOx. With fixed contents of Cu and Mn, we investigated the NH3-SCR process and the mechanism of action of the rare-earth species (i.e., Ce) in the system. Upon optimization of the content of Ce, the Ce/Mn/Cu-loaded Beta zeolite demonstrated enhanced low-temperature activity compared to samples loaded with Cu or Cu/Mn in the temperature range of 150–250 °C. When Ce was loaded in an appropriate proportion, it regulated the oxidation state of Cu, optimizing active adsorption species for NO and strengthening the strength of Brønsted acid sites in the catalyst. These synergetic effects led to improved NH3-SCR catalytic performance. This study can contribute to a better understanding of multiple metal-loaded zeolites in the NH3-SCR process and inform future design of Beta-type catalysts.

Morphology and valence state evolution of Cu: Unraveling the impact on nitric oxide electroreduction

Ammonia (NH3) serves as a critical component in the fertilizer industry and fume gas denitrification. However, the conventional NH3 production process, namely the Haber-Bosch process, leads to considerable energy consumption and waste gas emissions. To address this, electrocatalytic nitric oxide reduction reaction (NORR) has emerged as a promising strategy to bridge NH3 consumption to NH3 production, harnessing renewable electricity for a sustainable future. Copper (Cu) stands out as a prominent electrocatalyst for NO reduction, given its exceptional NH3 yield and selectivity. However, a crucial aspect that remains insufficiently explored is the effects of morphology and valence states of Cu on the NORR performance. In this investigation, we synthesized CuO nanowires (CuO-NF) and Cu nanocubes (Cu-NF) as cathodes through an in situ growth method. Remarkably, CuO-NF exhibited an impressive NH3 yield of 0.50 ± 0.02 mg cm−2 h−1 at −0.6 V vs. reversible hydrogen electrode (RHE) with faradaic efficiency of 29.68% ± 1.35%, surpassing that of Cu-NF (0.17 ± 0.01 mg cm−2 h−1, 16.18% ± 1.40%). Throughout the electroreduction process, secondary cubes were generated on the CuO-NF surface, preserving their nanosheet cluster morphology, sustained by an abundant supply of subsurface oxygen (s-O) even after an extended duration of 10 h, until s-O depletion ensued. Conversely, Cu-NF exhibited inadequate s-O content, leading to rapid crystal collapse within the same timeframe. The distinctive current–potential relationship, akin to a volcano-type curve, was attributed to distinct NO hydrogenation mechanisms. Further Tafel analysis revealed the exchange current density (i0) and standard heterogeneous rate constant (k0) for CuO-NF, yielding 3.44 × 10−6 A cm−2 and 3.77 × 10−6 cm−2 s−1 when NORR was driven by overpotentials. These findings revealed the potential of CuO-NF for NO reduction and provided insights into the intricate interplay between crystal morphology, valence states, and electrochemical performance.

Single-atom copper anchored on algal-based carbon induce peroxydisulfate activation for tetracycline degradation: DFT calculation and toxicity evaluation

Single-atom catalysts have wide application prospects in peroxydisulfate (PDS)-based advanced oxidation process to degrade organic pollutants, but its catalytic performance is limited due to its cost, Metal-N coordination number, and single-atom loading amount. Herein, a novel nitrogen doped algal-based carbon confined single-atom copper catalyst (Cu–N/C-SAC(S)) was synthesized using molten salt assisted pyrolysis and coupling with PDS to degrade tetracycline (TC). AC-HAADF-STEM and XAFS analysis proved that single atom Cu was loaded (Content 1.9 %) successfully and coordinated with two N and two C. XPS and XANES spectra analysis suggested that Cu atoms mainly existed in a positive divalent state in Cu–N/C-SAC(S). When the catalyst dosage of Cu–N/C-SAC(S) was 0.1 g/L, TC was almost completely removed. Moreover, Cu–N/C-SAC(S) had a broad pH adaptation range and strong ability against interference. Singlet oxygen (1O2), superoxide radicals (•O2−), and electron transfer had an important contribution for TC removal. DFT calculations confirmed that the activation process of Cu–N/C-SAC(S) producing SO4•− was easier than the nitrogen doped blue-green algal-based carbon (N-BGAC). In addition, Cu–N/C-SAC(S) possessed good recyclability and stability. The main degradation pathways of TC were analyzed, and the toxicity of the intermediates was calculated. This study provides a new solution strategy for the resource utilization of waste biomass, and provides technical support and theoretical guidance for the efficient application of single-atom catalysts in organic wastewater.

Sub-1 nm Cu2O Nanosheets for the Electrochemical CO2 Reduction and Valence State-Activity Relationship.

The copper-based (Cu-based) electrocatalytic materials effectively carry out the electrocatalytic carbon dioxide reduction reaction (CO2RR) toward C2+ products, yet the superiority and stability of the oxidation state of Cu are still worth studying. Herein, we designed and prepared three Cu-based electrocatalysts with different oxidation states to study the valence state-activity relationship. Among these Cu-based electrocatalysts, the Cu2O nanosheets with thickness of only 0.9 nm show an extremely high C2+ Faraday efficiency (FEC2+) of ∼81%, and the FEC2+ has an increase of 37% compared with the traditional CuOx phase. The ultrathin two-dimensional (2D) nanosheet structure with abundant oxygen vacancies can stabilize the oxidation state of Cu to improve the selectivity for C2+ products in CO2RR. In situ Raman spectroscopy and density functional theory calculations demonstrate that the rich Cu+ in the ultrathin 2D Cu2O nanosheets is the most suitable oxidation state for *CO adsorption and coverage on the catalyst surface, which promotes the C-C coupling reaction in CO2RR. This work provides an excellent catalyst for CO2RR toward C2+ products.

Ligand-mediated electrocatalytic activity of Cu-imidazolate coordination polymers for OER in water electrolysis

Copper is an Earth-abundant element promising for the synthesis of robust and efficient oxygen evolution reaction (OER) electrocatalysts. In this study, three Cu-imidazolate coordination polymers (Cu-Im, Cu-mIm, and Cu-bIm) are electrochemically synthesized and examined as OER catalysts whose activity can be modulated by the coordinating ligands of imidazole (Im), 2-methylimidazole (mIm), and benzimidazole (bIm). During the water electrolysis, Cu-Im and Cu-mIm are partially oxidized to form CuO particles, a well-known OER catalyst, while Cu-bIm does not. Due to the in situ formation of CuO during the electrolysis and weaker hydrophobicity of Im ligand, Cu-Im shows the highest electrocatalytic activity with a modest overpotential of 500 mV delivering a current density of 10 mA cm−2 and a Tafel slope of 215 mV dec−1 in 1 M KOH. On the contrary, the hydrophobic and anti-corrosion property of the bIm ligand stabilizes the Cu-bIm during the electrolysis without CuO formation. The hydrophobicity of the coordinating ligand influenced the electrocatalytic activity, resulting in the order of Cu-Im > Cu-mIm > Cu-bIm. Post-reaction analyses of the Cu-imidazolate coordination polymers reveal variations in the oxidation state of Cu, which has not been explored in previous studies. This work underlines that the ligand properties can regulate the catalytic activity of metal-ligand coordination polymer.

Synergistic effect of surface oxygen vacancies and hydroxyl groups on Cu-doped TiO2 photocatalyst for hydrogen evolution

The intricate nature of the titanium dioxide (TiO2) photocatalytic system, influenced by Cu doping, often yields conflicting outcomes. This study addresses this complexity by examining the impact of Cu ion doping in nanostructured TiO2 to augment its photocatalytic efficacy in hydrogen generation from ethanol-water mixtures. The improved performance is primarily attributed to the generation of oxygen vacancies (Ovac) within the TiO2 lattice. By adjusting the thermal processing parameters, the chemical state of Cu is modulated to optimize photocatalytic performance. Solid-state nuclear magnetic resonance (SSNMR) and density functional theory (DFT) calculations confirm that the presence of Ovac and hydroxyl groups (OH−) surface species not only facilitates local spatial charge separation but also enhances light absorption, thereby improving photocatalytic hydrogen evolution reaction (HER) rate up to 20.2 mmol h−1 g−1 under UV light. Furthermore, a proposed mechanism involves the participation of Ovac and OH− species, supported by Mott-Schottky (M − S) plots and ultraviolet photoelectron spectroscopy (UPS), revealing that Cu–TiO2 exhibits a lower flat band potential (Efb) and smaller work function compared to TiO2. This research underscores the pivotal role of Cu ions and Ovac:OH− in advancing the photocatalytic activity of TiO2-based crystals, imparting noteworthy implications for sustainable hydrogen generation.

Cu-coated graphitic carbon nitride (Cu/CN) with ideal photocatalytic and antibacterial properties

An improved photocatalytic activity of Graphitic carbon nitride (CN) photocatalyst was achieved by incorporating Cu2+ into CN in the presence of hyperbranched polyethylene amine (HPEI) as a capping agent. The addition of Cu to CN (CNHPEI+Cu) increased the photocatalytic degradation efficiency of wastewater dye pollutant methylene blue (MB) from 42 % to 95 %. E. coli and MS2 performed best in terms of inactivation to CNHPEI+Cu, achieving 5.5 ± 0.3 and 5.3 ± 0.1 log inactivation after 60 min of exposure, respectively. Excellent catalyst reusability and photocatalytic activity for MB in various types were obtained. To investigate the photocatalyst structure, morphology, optical, and photoelectric properties, we used X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), and photocatalytic activity. It was found through XRD and XPS that the prepared photocatalysts were made up of Cu-doped CN and that the valence state of Cu was Cu0. Under the visible part of the solar spectrum (>400 nm), the N2 adsorption-desorption isotherms of pure CN, CNHPEI, and CNHPEI+Cu showed that copper did not alter the microstructure of pure CN. The photocatalytic activity of CNHPEI+Cu was improved by incorporating Cu0 into CN, as this reduces the rate of electron-hole recombination in pure CN and accelerates the separation of electron-hole pairs. Electron spin resonance (ESR) spin trap experiments on the production of reactive oxygen species (ROS) from CNHPEI+Cu under visible light indicate that the presence of superoxide radicals (O2•−), hydroxyl radicals (•OH) and holes could enhance the photocatalytic activity of the material.