Nanoporous Au Thin Films on Si Photoelectrodes for Selective and Efficient Photoelectrochemical CO2 Reduction

An Si photoelectrode with a nanoporous Au thin film for highly selective and efficient photoelectrochemical (PEC) CO₂ reduction reaction (CO₂RR) is presented. The nanoporous Au thin film is formed by electrochemical reduction of an anodized Au thin film. The electrochemical treatments of the Au thin film critically improve CO₂ reduction catalytic activity of Au catalysts and exhibit CO Faradaic efficiency of 96% at 480 mV of overpotential. To apply the electrochemical pretreatment of Au films for PEC CO₂RR, a new Si photoelectrode design with mesh‐type co‐catalysts independently wired at the front and the back of the photoelectrode is demonstrated. Due to the superior CO₂RR activity of the nanoporous Au mesh and high photovoltage from Si, the Si photoelectrode with the nanoporous Au thin film mesh shows conversion of CO₂ to CO with 91% Faradaic efficiency at positive potential than the CO₂/CO equilibrium potential.     

In-Situ Constructuring of Copper-Doped Bismuth Catalyst for Highly Efficient CO2 Electrolysis to Formate in Ampere-Level

CO₂ electrochemical reduction (CO₂RR) can mitigate environmental issues while providing valuable products, yet challenging in activity, selectivity, and stability. Here, a CuS-Bi₂S₃ heterojunction precursor is reported that can in situ reconstruct to Cu-doped Bismuth (CDB) electrocatalyst during CO₂RR. The CDB exhibits an industrial-compatible current density of −1.1 A cm⁻² and a record-high formate formation rate of 21.0 mmol h⁻¹ cm⁻² at −0.86 V versus the reversible hydrogen electrode toward CO₂RR to formate, dramatically outperforming currently reported catalysts. Importantly, the ultrawide potential region of 1050 mV with high formate Faradaic efficiency of over 90% and superior long-term stability for more than 100 h at −400 mA cm⁻² can also be realized. Experimental and theoretical studies reveal that the remarkable CO₂RR performance of CDB results from the doping effect of Cu which optimizes adsorption of the *OCHO and boosts the structural stability of metallic bismuth catalyst. This study provides valuable inspiration for the design of element-doping electrocatalysts to enhance catalytic activity and durability.     

Multi-Shell Copper Catalysts for Selective Electroreduction of CO2 to Multicarbon Chemicals

Electrocatalytic CO₂ reduction (CO₂R) coupled with renewable electricity has been considered as a promising route for the sustainability transition of energy and chemical industries. However, the unsatisfactory yield of desired products, particularly multicarbon (C₂₊) products, has hindered the implementation of this technology. This work describes a strategy to enhance the yield of C₂₊ product formation in CO₂R by utilizing spatial confinement effects. The finite element simulation results suggest that increasing the number of shells in the catalyst wil lead to a high local concentration of *CO and promotes the formation of C₂₊ products. Inspired by this, Cu nanoparticles are synthesized with desired hollow multi-shell structures. The CO₂ reduction results confirm that as the number of shells increase, the hollow multi-shell copper catalysts exhibit improved selectivity toward C₂₊ products. Specifically, the Cu catalyst with 4.4-shell achieved a high selectivity of over 80% toward C₂₊ at a current density of 900 mA cm⁻². Evidence from in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy unveils that the multi-shell Cu catalyst exhibits an enhanced *CO_atop coverage and the stronger interaction with *CO_atop compared to commercial Cu, confirming the simulation results. Overall, the work promises an effective approach for boosting CO₂R selectivity toward value-added chemicals.     

A membrane-free baffled microbial fuel cell for cathodic reduction of Cu(II) with electricity generation

A membrane-free baffled microbial fuel cell (MFC) was developed to treat synthetic Cu(II) sulfate containing wastewater in cathode chamber and synthetic glucose-containing wastewater fed to anode chamber. Maximum power density of 314 mW/m³ with columbic efficiency of 5.3% was obtained using initial Cu²⁺ concentration of 6400 mg/L. Higher current density favored the cathodic reduction of Cu²⁺, and removal of Cu²⁺ by 70% was observed within 144 h using initial concentration of 500 mg/L. Powder X-ray diffraction (XRD) analysis indicated that the Cu²⁺ was reduced to Cu₂O or Cu₂O plus Cu which deposited on the cathode, and the deficient cathodic reducibility resulted in the formation of Cu₄(OH)₆SO₄ at high initial Cu²⁺ concentration (500-6400 mg/L). This study suggested a novel low-cost approach to remove and recover Cu(II) from Cu²⁺-containing wastewater using MFC-type reactor.     

Atomic‐Scale Spacing between Copper Facets for the Electrochemical Reduction of Carbon Dioxide

Copper (Cu) offers a means for producing value‐added fuels through the electrochemical reduction of carbon dioxide (CO₂), i.e., the CO₂ reduction reaction (CO₂RR), but designing Cu catalysts with significant Faradaic efficiency to C₂₊ products remains as a great challenge. This work demonstrates that the high activity and selectivity of Cu to C₂₊ products can be achieved by atomic‐scale spacings between two facets of Cu particles. These spacings are created by lithiating CuO_x particles, removing lithium oxides formed, and electrochemically reducing CuO_x to metallic Cu. Also, the range of spacing (d_s) is confirmed via the 3D tomographs using the Cs‐corrected scanning transmission electron microscopy (3D tomo‐STEM), and the operando X‐ray absorption spectra show that oxidized Cu reduces to the metallic state during the CO₂RR. Moreover, control of d_s to 5–6 Å allows a current density exceeding that of unmodified CuO_x nanoparticles by about 12 folds and a Faradaic efficiency of ≈80% to C₂₊. Density functional theory calculations support that d_s of 5–6 Å maximizes the binding energies of CO₂ reduction intermediates and promotes C–C coupling reactions. Consequently, this study suggests that control of d_s can be used to realize the high activity and C₂₊ product selectivity for the CO₂RR.     

Intermediates Adsorption Engineering of CO2 Electroreduction Reaction in Highly Selective Heterostructure Cu‐Based Electrocatalysts for CO Production

The challenge in the artificial CO₂ reduction to fuel is achieving high selective electrocatalysts. Here, a highly selective Cu₂O/CuO heterostructure electrocatalyst is developed for CO₂ electroreduction. The Cu₂O/CuO nanowires modified by Ni nanoparticles exhibit superior catalytic performance with high faradic efficiency (95% for CO). Theoretical and experimental analyses show that the hybridization of Cu₂O/CuO nanowires and Ni nanoparticles can not only adjust the d‐band center of electrocatalysts to enhance the intrinsic catalytic activity but also improve the adsorption of COOH* intermediates and suppress the hydrogen evolution reaction to promote the CO conversion efficiency during CO₂ reduction reaction. An in situ Raman spectroscopic study further confirms the existence of COOH* species and the engineering intermediates adsorption. This work offers new insights for facile designing of nonprecious transition metal compound heterostructure for CO₂ reduction reaction through adjusting the reaction pathway.     

Free-standing Stanene for High Selectivity of Formate in Electrocatalytic Carbon Dioxide Reduction Reaction

As well-known electrocatalysts with good catalytic efficiency for carbon dioxide reduction reaction (CO₂RR) towards the production of formate, tin (Sn)-based catalysts have aroused broad concern. Here, free-standing porous stanene is synthesized for the first time by a facile wet chemical method, and its excellent electrocatalytic performance for formate (HCOO⁻) formation in CO₂RR is demonstrated. High Faradaic efficiency (F.E., 93% at −930 mV versus reversible hydrogen electrode (RHE)) can be achieved in the CO₂RR catalyzed by stanene in 0.5 m KHCO₃ aqueous solution. The in situ Mössbauer spectra reveal that zero-valent Sn aids in improving the selectivity of formate production. Furthermore, density functional theory calculations suggest that the high selectivity of HCOO⁻ of CO₂RR on stanene mainly originates from the edge sites on Sn (100). To further explore the practicability of the stanene-based catalysts for CO₂RR, stanene decorated by 3 wt% BP-2000 is prepared, showing an excellent F.E. of 98% at −930 mV versus RHE due to the higher exposure of catalytic active sites. These new findings of the activity origination and reaction mechanism of stanene contribute to the deeper understanding of Sn-based catalysts for CO₂RR, which is beneficial for the future designation of highly efficient CO₂RR catalysts.     

CeNCl-CeO2 Heterojunction-Modified Ni Catalysts for Efficient Electroreduction of CO2 to CO

Renewable-electricity-powered electrochemical CO₂ reduction (CO₂RR) is considered one of the most promising ways to convert exhaust CO₂ into value-added chemicals and fuels. Among various CO₂RR products, CO is of great significance since it can be directly used as feedstock to produce chemical products through the Fischer–Tropsch process. However, the CO₂-to-CO electrocatalytic process is often accompanied by a kinetically competing side reaction: H₂ evolution reaction (HER). Designing electrocatalysts with tunable electronic structures is an attractive strategy to enhance CO selectivity. In this work, a CeNCl-CeO₂ heterojunction-modified Ni catalyst is successfully synthesized with high CO₂RR catalytic performance by the impregnation-calcination method. Benefiting from the strong electron interaction between the CeNCl-CeO₂ heterojunction and Ni nanoparticles (NPs), the catalytic performance is greatly improved. Maximal CO Faradaic efficiency (FE) is up to 90% at −0.8 V (vs RHE), plus good stability close to 12 h. Detailed electrochemical tests and density functional theory (DFT) calculation results reveal that the introduction of the CeNCl-CeO₂ heterojunction tunes the electronic structure of Ni NPs. The positively charged Ni center leads to an enhanced local electronic structure, thus promoting the activation of CO₂ and the adsorption of ^*COOH.     

Improvement of photoluminescence of Cu+ ion in Li2SO4

The synthesis of the Li₂SO₄: Cu phosphor using a wet chemical method is reported here. The XRD technique showed the crystalline nature of the prepared material. The presence of Na and K in the host affected the observed photoluminescence characteristics of Li₂SO₄: Cu. Photoluminsecent emission spectra of Li₂SO₄: Cu phosphor showed a very strong prominet peak at 387 nm in the indigo region due to 3d⁹ 4 s¹ ? 3d¹⁰ transition of the Cu⁺ ion. The increase in peak intensity of the PL spectrum suggests that Cu⁺ acts as the luminescence center in the present matrix. Copyright © 2010 John Wiley & Sons, Ltd.     

Extended Light Harvesting with Dual Cu2O‐Based Photocathodes for High Efficiency Water Splitting

Cu₂O is one of the most promising light absorbing materials for solar energy conversion. Previous studies with Cu₂O for water splitting usually deliver high photocurrent or high photovoltage, but not both. Here, a Cu₂O/Ga₂O₃/TiO₂/RuO_x photocathode that benefits from a high quality thermally oxidized Cu₂O layer and good band alignment of the Ga₂O₃ buffer layer is reported, yielding a photocurrent of 6 mA cm^?2 at 0 V versus reversible hydrogen electrode (RHE), an onset potential of 0.9 V versus RHE, and 3.5 mA cm^?2 at 0.5 V versus RHE. The quantum efficiency spectrum (incident photon to current efficiency, IPCE) reveals a dramatically improved green/red response and a decreased blue response compared with electrodeposited Cu₂O films. Light intensity dependence and photocurrent transient studies enable the identification of the limitations in the performance. Due to the complementary IPCE curves of thermally oxidized and electrodeposited Cu₂O photocathodes, a dual photocathode is fabricated to maximize the absorption over the entire range of above band gap radiation. Photocurrents of 7 mA cm^?2 at 0 V versus RHE are obtained in the dual photocathodes, with an onset potential of 0.9 V versus RHE and a thermodynamically based energy conversion efficiency of 1.9%.     

A Nanosheet Array of Cu2Se Intercalation Compound with Expanded Interlayer Space for Sodium Ion Storage

Intercalation chemistry/engineering has been widely investigated in the development of electrochemical energy storage. Graphite, as an old intercalation host, is receiving vigorous attention again via a new halogen intercalation. Whereas, exploiting new intercalation hosts and optimizing the intercalation effect still remains a great challenge. This study fabricates a Cu₂Se intercalation compound showing expanded interlayer space and nanosheet array features by using a green growth approach, in which cetyltrimethyl ammonium bromide (CTAB) is inserted into Cu₂Se at an ambient temperature. When acting as an electrode material for sodium‐ion batteries, the Cu₂Se–CTAB nanosheet arrays exhibit excellent discharge capacity and rate capability (426.0 mAh g^?1 at 0.1 A g^?1 and 238.1 mAh g^?1 at 30 A g^?1), as well as high capacity retention of ≈90% at 20 A g^?1 after 6500 cycles. Benefiting from the porous array architecture, the transport of electrolytes is facilitated on the surface of Cu₂Se nanosheets. In particular, the CTAB intercalated in the interlayer space of Cu₂Se can increase its buffer space, stabilize the polyselenide shuttle, and prevent the fast growth of Cu nanoparticles during its electrochemical process.     

Synthesis,structures and reactivity of N-donor-functionalised Cu(I) aryloxides

The preparation and characterisation of the Cu(I) aryloxides [Cu₁₆(3-pyO)₁₆(dppm)₈] (1), [{Cu₂(2-pyO)₂(dppm)}₂] (2) and [{Cu₃(μ₃-6-OQ)₂(dppm)₃}{(6-HOQ)₂(μ-6-OQ)}] (3) (dppm = 1,2-bis-diphenylphosphinomethane, 6-HOQ = 6-hydroxyquinoline, py = pyridine) are described. A first attempt to employ organic anhydrides in insertion reactions with Cu(I) aryloxides was made producing the one-dimensional coordination polymer 1/_∞[Cu₃(3-pyO)(CO₂C₂H₄Boc)(dppm⁻)(dppm)]_∞ (4) (Boc = tert-butoxycarbonyl).     

Effects of Copper on T-Type Ca<Superscript>2+</Superscript> Channels in Mouse Spermatogenic Cells

Low voltage-activated, rapidly inactivating T-type Ca²⁺ channels are found in a variety of cells, where they regulate electrical activity and Ca²⁺ entry. In whole-cell patch-clamp recordings from mouse spermatogenic cells, trace element copper (Cu²⁺) inhibited T-type Ca²⁺ current (I _T-Ca) with IC₅₀ of 12.06 μM. Inhibition of I _T-Ca by Cu²⁺ was concentration-dependent and mildly voltage-dependent. When voltage stepped to −20 mV, Cu²⁺ (10 μM) inhibited I _T-Ca by 49.6 ± 4.1%. Inhibition of I _T-Ca by Cu²⁺ was accompanied by a shift of −2.23 mV in the voltage dependence of steady-state inactivation. Cu²⁺ upshifted the current–voltage (I-V) curve. To know the change of the gating kinetics of T-type Ca²⁺ channels, we analyzed the effect of Cu²⁺ on activation, inactivation, deactivation and reactivation of T-type Ca²⁺ channels. Since T-type Ca²⁺ channels are a key component in capacitation and the acrosome reaction, our data suggest that Cu²⁺ can affect male reproductive function through T-type Ca²⁺ channels as a preconception contraceptive material.     

Metal‐Free Artificial Photosynthesis of Carbon Monoxide Using N‐Doped ZnTe Nanorod Photocathode Decorated with N‐Doped Carbon Electrocatalyst Layer

An artificial photosynthesis system based on N‐doped ZnTe nanorods decorated with an N‐doped carbon electrocatalyst layer is fabricated via an all‐solution process for the selective conversion of CO₂ to CO. Substitutional N‐doping into the ZnTe lattice decreases the bandgap slightly and improves the charge transfer characteristics, leading to enhanced photoelectrochemical activity. Remarkable N‐doping effects are also demonstrated by the N‐doped carbon layer that promotes selective CO₂‐to‐CO conversion instead of undesired water‐to‐H₂ reduction by providing active sites for CO₂ adsorption and activation, even in the absence of metallic redox centers. The photocathode shows promising performance in photocurrent generation (?1.21 mA cm^?2 at ?0.11 V_RHE), CO selectivity (dominant CO production of ≈72%), minor H₂ reduction (≈20%), and stability (corrosion suppression). The metal‐free electrocatalyst/photocatalyst combination prepared via a cost‐effective solution process exhibits high performance due to synergistic effects between them, and thus may find application in practical solar fuel production.     

A rhodamine‐triazole fluorescent chemodosimeter for Cu2+ detection and its application in bioimaging

A rhodamine‐based fluorescent chemodosimeter rhodamine hydrazide‐triazole (RHT) tethered with a triazole moiety was developed for Cu²⁺ detection. In aqueous medium, the RHT probe exhibited high selectivity and sensitivity toward Cu²⁺ among other metal ions. The addition of Cu²⁺ triggered a fluorescence emission of RHT by 384‐fold (Φ = 0.33) based on a ring‐opening process and a subsequent hydrolysis reaction. Moreover, RHT also showed a selective colorimetric response toward Cu²⁺ from colorless solution to pink, readily observed with the naked eye. The limit of detection of RHT for Cu²⁺ was calculated to be 1 nM (0.06 ppb). RHT was successfully demonstrated to detect Cu²⁺ in Chang liver cells by confocal fluorescence microscopy.     

Organic-inorganic hybrid materials constructed from Cu(II)-organonitrogen coordination complex cations and oxovanadium-arsonate subunits

The hydrothermal reactions of NH₄VO₃, Cu(NO₃)₂·H₂O or Cu(CH₃CO₂)₂·H₂O As₂O₅ and the appropriate organonitrogen ligand in the presence of HF as mineralizer yield a series of bimetallic oxides of the Cu/V/O/As family. The materials [Cu(bpy)(VO₂)(AsO₄)] (1) and [Cu(bpy)VO₂(OH)(AsO₄H)]·H₂O (2·H₂O) are one-dimensional (bpy = 2,2′-bipyridine). While phase 1 is constructed from chains decorated by {Cu(bpy)}²⁺ groups, compound 2 consists of {V₂O₄(OH)₂(AsO₄H)₂}²⁻ clusters linked through {Cu(bpy)}²⁺ subunits. In contrast, the structure of [Cu₂(bpyrm)(VO₂)₂(AsO₄)₂]·H₂O (3·H₂O) is three-dimensional, consisting of layers, linked through {Cu₂(bpyrm)}⁴⁺ rods (bpyrm = bipyrimidine).     

A colorimetric probe for detection of Cu2+ by the naked eye and application in test paper

A novel colorimetric probe RP1 was synthesized using rhodamine derivatives and heterocyclic compounds for the purpose of detecting Cu²⁺. RP1 showed good selectivity, high sensitivity and affinity toward Cu²⁺ over other competing ions in CH₃OH–H₂O (1/1, v/v) solution. Absorbance intensity showed a good linear fit between probe R1 and Cu²⁺ over the concentration range 1–8 μM and the association constant was also calculated to be 1.145 × 10⁵ M^?1. The sensing mechanism was deduced using Job's plot, Fourier transform infrared spectroscopy, and density functional theory studies. In addition, the colorimetric experiment indicated that probe RP1 could be made into test paper to detect Cu²⁺ with a colour change from colourless to pink.     

Highly fluorescent au nanoclusters: Electrostatically induced phase transfer synthesis for Cu2+ sensing

This paper reports a convenient method for the synthesis of highly fluorescent Au nanoclusters (NCs) via electrostatically induced phase transfer. Furthermore, on the basis of an aggregation‐induced fluorescence quenching mechanism, the potential application for Cu²⁺ sensing on the fluorescence emission of the Au NCs is discussed. These prepared fluorescent Au NCs offer acceptable sensitivity, high selectivity, and a limit of quantitation of 0.02 μM for the measurement of Cu²⁺, which is lower than the maximum level (1 ppm, equals to 15.6 μM) of Cu²⁺ permitted in drinking water in China. This study contributes to the further development of practical applications with fluorescent NCs.     

Synthesis and characterization of new oligomeric and polymeric complexes based on the [Cu(bpca)] unit [Hbpca = bis(2-pyridylcarbonyl)amine]

Five novel bpca-based Cu(II) polynuclear coordination compounds [Hbpca = bis(2-pyridylcarbonyl)amine] were prepared using the [Cu(bpca)(H₂O)₂](NO₃)·2H₂O (1) building block and characterized by single crystal X-ray diffraction. We have also isolated and characterized two new crystal forms of the starting species, with lower water contents. Three of the new products are dinuclear complexes obtained by reacting 1 with different rigid or flexible spacer ligands: [Cu₂(bpca)₂(H₂O)₂(bipy)](NO₃)₂·6H₂O (2) (bipy = 4,4′-bipyridine) and [Cu₂(bpca)₂(H₂O)₂(bpete)](NO₃)₂·xH₂O (3) [bpete = (E)-1,2-di(pyridin-4-yl)ethane] are linear dumbbell-like species with Cu?Cu separations of 11.075 and 13.275 Å, respectively. The third dinuclear compound, [Cu₂(bpca)₂(H₂O)₂(bpx)](NO₃)₂·8H₂O (4) [bpx = 1,4-bis((1H-pyrazol-1-yl)methyl)benzene], with the flexible bpx ligand, assumes an unusual S-shaped conformation and shows a quite shorter Cu?Cu contact of 6.869 Å only. We have also obtained a chiral 1D neutral polymeric complex, [Cu₃(bpca)₂(bipy)₃(NO₃)₄]·6H₂O (5), that shows a central linear -Cu-bipy-Cu- chain, with all these Cu atoms connected to two lateral [Cu(bpca)(NO₃)₂]⁻ groups on two opposite sides by means of bipy spacers. An unprecedented type of Cu(II) neutral trinuclear complex, [Cu₃(bpca)₂(H₂O)₂(NO₃)₂] (6), was obtained which has a centrosymmetric structure with two external [Cu(bpca)(NO₃)₂]⁻ units chelating on a central copper atom via the two pairs of carbonyl groups of the bpca ligands. The central metal is octahedral with two axial water molecules, while the two lateral Cu atoms are in square pyramidal geometry; the Cu?Cu separation is 5.205 Å. The magnetic properties of 6 have been rationalized through a ferromagnetic coupling between the central metal ion and the peripheral ones which are coupled by a smaller antiferromagnetic interaction. DFT calculations have been also performed in order to give a better insight into magnetic interactions.     

Exploiting Synergistic Effect by Integrating Ruthenium–Copper Nanoparticles Highly Co‐Dispersed on Graphene as Efficient Air Cathodes for Li–CO2 Batteries

Li–CO₂ batteries are attractive electrical energy storage devices; however, they still suffer from unsatisfactory electrochemical performance, and the kinetics of CO₂ reduction and evolution reactions must be improved significantly. Herein, a composite of ruthenium–copper nanoparticles highly co‐dispersed on graphene (Ru–Cu–G) as efficient air cathodes for Li–CO₂ batteries is designed. The Li–CO₂ batteries with Ru–Cu–G cathodes exhibit ultra‐low overpotential and can be operated for 100 cycles with a fixed capacity of 1000 mAh g^?1 at 200 and 400 mA g^?1. The synergistic effect between Ru and Cu not only regulates the growth of discharge products, but also promotes CO₂ reduction and evolution reactions by changing the electron cloud density of the surface between Ru and Cu. This work may provide new directions and strategies for developing highly efficient air cathodes for Li–CO₂ batteries, or even practical Li–air batteries.