新型的钛基Ni-Sn/Ti电极的制备及对甲醇氧化反应的电催化活性

利用电热法,一步制备出新型的钛基Ni-Sn/Ti电极(Ni8Sn/Ti, Ni7Sn3/Ti 和 Ni/Ti)。扫描电镜（SEM）图像表明,催化剂以片状的纳米颗粒形式沉积于钛基体上。利用电化学伏安技术、电位阶跃法和电化学交流阻抗谱（EIS）,研究了这些电极在1mol.L�1NaOH溶液中对甲醇氧化反应的电催化活性。研究表明,与Ni7Sn3/Ti,Ni/Ti以及多晶镍电极相比,Ni8Sn/Ti电极对甲醇氧化反应表现出更高的阳极氧化电流和更低的起始电位。EIS分析表明,在本文所考察的阳极电位和甲醇浓度下,Ni8Sn/Ti电极对甲醇氧化反应显示出极低的电荷传递电阻。结果表明,这种新型的钛基Ni8Sn/Ti电极对甲醇氧化反应具有极高的电催化活性。     

Selective CO2 Electroreduction to Ethylene and Multicarbon Alcohols via Electrolyte‐Driven Nanostructuring

Production of multicarbon products (C₂₊) from CO₂ electroreduction reaction (CO₂RR) is highly desirable for storing renewable energy and reducing carbon emission. The electrochemical synthesis of CO₂RR catalysts that are highly selective for C₂₊ products via electrolyte‐driven nanostructuring is presented. Nanostructured Cu catalysts synthesized in the presence of specific anions selectively convert CO₂ into ethylene and multicarbon alcohols in aqueous 0.1 m KHCO₃ solution, with the iodine‐modified catalyst displaying the highest Faradaic efficiency of 80 % and a partial geometric current density of ca. 31.2 mA cm^?2 for C₂₊ products at ?0.9 V vs. RHE. Operando X‐ray absorption spectroscopy and quasi in situ X‐ray photoelectron spectroscopy measurements revealed that the high C₂₊ selectivity of these nanostructured Cu catalysts can be attributed to the highly roughened surface morphology induced by the synthesis, presence of subsurface oxygen and Cu⁺ species, and the adsorbed halides.     

Mechanistic Elucidations of Highly Dispersed Metalloporphyrin Metal-Organic Framework Catalysts for CO2 Electroreduction

Immobilization of porphyrin complexes into crystalline metal–organic frameworks (MOFs) enables high exposure of porphyrin active sites for CO₂ electroreduction. Herein, well-dispersed iron-porphyrin-based MOF (PCN-222(Fe)) on carbon-based electrodes revealed optimal turnover frequencies for CO₂ electroreduction to CO at 1 wt.% catalyst loading, beyond which the intrinsic catalyst activity declined due to CO₂ mass transport limitations. In situ Raman suggested that PCN-222(Fe) maintained its structure under electrochemical bias, permitting mechanistic investigations. These revealed a stepwise electron transfer-proton transfer mechanism for CO₂ electroreduction on PCN-222(Fe) electrodes, which followed a shift from a rate-limiting electron transfer to CO₂ mass transfer as the potential increased from −0.6 V to −1.0 V vs. RHE. Our results demonstrate how intrinsic catalytic investigations and in situ spectroscopy are needed to elucidate CO₂ electroreduction mechanisms on PCN-222(Fe) MOFs.     

Nickel Doping in Atomically Thin Tin Disulfide Nanosheets Enables Highly Efficient CO2 Reduction

Engineering electronic properties by elemental doping is a direct strategy to design efficient catalysts towards CO₂ electroreduction. Atomically thin SnS₂ nanosheets were modified by Ni doping for efficient electroreduction of CO₂. The introduction of Ni into SnS₂ nanosheets significantly enhanced the current density and Faradaic efficiency for carbonaceous product relative to pristine SnS₂ nanosheets. When the Ni content was 5 atm %, the Ni‐doped SnS₂ nanosheets achieved a remarkable Faradaic efficiency of 93 % for carbonaceous product with a current density of 19.6 mA cm^?2 at ?0.9 V vs. RHE. A mechanistic study revealed that the Ni doping gave rise to a defect level and lowered the work function of SnS₂ nanosheets, resulting in the promoted CO₂ activation and thus improved performance in CO₂ electroreduction.     

Direct electrochemistry of recombinant tobacco peroxidase on gold

Direct electron transfer (DET) reactions of recombinant tobacco peroxidase (rTOP), namely direct electroreduction of Compound I/Compound II and heme Fe^3+/2+ conversion, were studied on gold electrodes. rTOP of wild type, non-glycosylated, was produced using an Escherichia coli expression system. At pH 5.0, the redox potential for direct electrochemical transformation of the Fe^3+/2+ of the peroxidase heme was −143 mV vs. AgAgCl, and 0.26 ± 0.07 pmol of the adsorbed rTOP were in DET contact with the gold electrode. The total amount of the adsorbed rTOP estimated from QCM data was 53 ± 5 pmol/cm² or 1.67 pmol when referred to the surface area of the electrodes used for electrochemical measurements. Of 1.67 pmol of adsorbed rTOP, only 0.76 pmol were catalytically active. DET between Au and the enzyme was also studied in the reaction of the bioelectrocatalytic reduction of H₂O₂ by cyclic voltammetry and amperometric detection of H₂O₂ at +50 mV with rTOP-modified Au electrodes placed in a wall-jet flow-through electrochemical cell. Maximal bioelectrocatalytic current response of the rTOP-modified gold electrodes to H₂O₂ was observed at pH 5.0 and stemmed from its bioelectrocatalytic reduction based on DET between Au and the active site of rTOP. Kinetic analysis of the DET reactions gave 52% of the adsorbed rTOP molecules active in DET reactions (0.4 pmol of adsorbed catalytically active rTOP, correspondingly), which correlated well with the non-catalytic-voltammetry data. DET was characterised by a heterogeneous ET rate constant of 13.2 s⁻¹, if one takes into account the QCM data, and 19.6 s⁻¹, if the amount of rTOP estimated from the data on DET transformation of Fe^3+/2+ couple of rTOP is considered. The sensitivity for H₂O₂ obtained for the rTOP-modified Au electrodes was 0.7 ± 0.1 A M⁻¹ cm⁻². These are the first ever-reported data on DET reactions of anionic plant peroxidases on bare gold electrodes.     

In situ infrared spectroscopic investigations on the electrochemical properties of prussian blue-polyaniline-modified electrodes with various anionic Fe(II) complexes working as a mediator for the electroreduction of CO2

Various Fe(II) complexes have been incorporated into Prussian blue (PB)|polyaniline (PAn)-modified electrodes, and their spectroelectrochemical properties been investigated using in situ and ex situ FTIR methods. It is shown that large anionic complexes once incorporated in the PAn matrix are not dedoped during the potential cycling and the charge balance is maintained by dedoping or incorporating electrolyte cations. This electrode system was applied to the electrocatalytic reduction of CO₂ in aqueous solution, and the reduction products were identified by taking in situ FTIR spectra during the anodic stripping. At potentials higher than 0 V, the IR bands associated with the loss of carboxylic acid at 1362 cm⁻¹ and the gain of CO₂ at 2343 cm⁻¹ were simultaneously observed, indicating that the CO₂ was derived from the reoxidation of carboxylic acid. It is therefore confirmed that CO₂ can be reduced to organic species including carboxylic acid on the PB|PAn-modified electrode with anionic Fe(II) complexes in aqueous solution, with an indication that the existence of the anionic metal complex is essential to such mediated reduction of CO₂.     

Electrodes modified with iron porphyrin and carbon nanotubes: application to CO2 reduction and mechanism of synergistic electrocatalysis

Electrodes modified with iron porphyrin and carbon nanotubes (FeP–CNTs) were prepared and used for CO₂ electroreduction. The adsorption of iron porphyrin onto the multiwalled carbon nanotubes was characterized by scanning electron microscopy and ultraviolet and visible spectroscopy. The electrochemical properties of the modified electrodes for CO₂ reduction were investigated by cyclic voltammetry and CO₂ electrolysis. The FeP–CNT electrodes exhibited less negative cathode potential and higher reaction rate than the electrodes modified only with iron porphyrin or carbon nanotubes. A mechanism of the synergistic catalysis was proposed and studied by electrochemical impedance spectroscopy and electron paramagnetic resonance. The direct electron transfer between iron porphyrin and carbon nanotubes was examined. The current study shed light on the mechanism of synergistic catalysis between CNTs and metalloporphyrin, and the iron porphyrin–CNT-modified electrodes showed great potential in the efficient CO₂ electroreduction.     

A Resin-Supported Formate Catalyst for the Transformative Reduction of Carbon Dioxide with Hydrosilanes

A heterogeneous formate anion catalyst for the transformative reduction of carbon dioxide (CO₂) based on a polystyrene and divinylbenzene copolymer modified with alkylammonium formate was prepared from a widely available anion exchange resin. The catalyst preparation was easy and the characterization was carried out by using elemental analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and solid-state ¹³C cross-polarization/magic-angle spinning nuclear magnetic resonance (¹³C CP/MAS NMR) spectroscopy. The catalyst displayed good catalytic activity for the direct reduction of CO₂ with hydrosilanes, tunably yielding silylformate or methoxysilane products depending on the hydrosilanes used. The catalyst was also active for the reductive insertion of CO₂ into both primary and secondary amines. The catalytic activity of the resin-supported formate can be predicted from the FTIR spectra of the catalyst, probably because of the difference in the ionic interaction strength between the supported alkylammonium cations and formate anions. The ion pair density is thought to influence the catalytic activity, as shown by the elemental and solid-state ¹³C NMR analyses.     

Highly efficient In–Sn alloy catalysts for electrochemical reduction of CO2 to formate

Gas diffusion electrodes (GDEs), including GDE-In_0.90Sn_0.10, GDE-In_0.47Sn_0.53 and GDE-In_0.22Sn_0.78, were prepared by electrodeposition of In–Sn alloys on carbon fiber paper, and then used to explore the electroreduction of CO₂ to formate in aqueous solution. Compared with commercial indium or Sn foil catalysts, the GDE-In_0.90Sn_0.10 electrode in particular is shown to have excellent catalytic performance towards electroreduction of CO₂ to formate, with a high Faradaic efficiency (~ 92%). More importantly, the catalytic activity of GDE-In_0.90Sn_0.10 remained reasonably stable over a 22-hour period of electrolysis, and a relatively high electrolytic current density (15 mA cm^− 2) was obtained in an aqueous medium, demonstrating its potential for electrochemical reduction of CO₂ to formate.     

Electrochemical Reduction of CO2 at Coinage Metal Nanodendrites in Aqueous Ethanolamine

Electrocatalytic reduction of CO₂ into usable chemicals is a promising path to address climate change and energy challenges. Herein, we demonstrate the synthesis of unique coinage metal (Cu, Ag, and Au) nanodendrites (NDs) via a facile galvanic replacement reaction (GRR), which can be effective electrocatalysts for the reduction of CO₂ in an ethanolamine (EA) solution. Each metal ND surface was directly grown on glassy-carbon (GC) substrates from a mixture of Zn dust and the respective precursor solution. The electrocatalytic activities of the synthesized ND surfaces were optimized for CO₂ reduction in EA solution by varying their composition. It was determined that a 0.05 mol fraction of EA exhibited the highest catalytic activity for all metal NDs. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) techniques showed that metal-ND electrodes possessed higher current densities, lower onset potentials and lower charge-transfer resistances for CO₂ reduction than their smooth polycrystalline electrode counterparts, indicating improved CO₂ reduction catalytic activity. It was determined, using FTIR and NMR spectroscopy, that formate was produced as a result of the CO₂ reduction.     

Three new copper(II)–nickel(II) heterodinuclear complexes with the <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N′</Emphasis>-bis(2-pyridyl-ethyl)oxamide dianion. Syntheses,spectra, and magnetic properties

Three new Cu(II)–Ni(II) heterodinuclear complexes: [Cu(PMoxd)Ni(phen)₂](ClO₄)₂ (1), [Cu(PMoxd)Ni(NO₂-phen)₂](ClO₄)₂ (2), [Cu(PEoxd)Ni(Me₂-bpy)₂](ClO₄)₂ (3), [where Cu(PMoxd)=N,N′-bis(pyridyl-methyl)oxamidatocopper(II), Cu(PExod)=N,N′-bis(2-pyridyl-ethyl)oxamidatocopper(II), phen=1,10-phenanthroline and NO₂-phen=5-nitro-1,10-phenanthroline and bpy=2,2′-bipyridine] were prepared and characterized by i.r. and electronic spectra, and by magnetic properties. The magnetic analysis was carried out by means of the theoretical expression of the magnetic susceptibility deduced from the spin Hamiltonian H=−2JS₁S₂, leading to J=−70.83 cm⁻¹ (1); −56.23 cm⁻¹ (2); −57.30 cm⁻¹ (3), indicating a weak antiferromagnetic spin–exchange interaction between Cu(II) and Ni(II) ions within three complexes.     

In situ FTIR spectroscopic study of ethanol oxidation on Pt(111)/Rh/Sn surface. The anion effect

In situ Fourier Transform Infrared (FTIR) spectroscopy was used to study the anion effect in ethanol oxidation on Pt (111) surface modified by rhodium and tin, Pt(111)/Rh/Sn. The in situ FTIR spectra showed that ethanol oxidation reaction pathway is strongly influenced by the nature of the electrolyte anion. In perchloric and sulfuric acid electrolytes were observed the formation of acetaldehyde, acetic acid and CO₂; however in phosphoric acid the acetic acid is not observed. The sulfuric acid is the most favorable electrolyte for acetaldehyde and CO₂ formation.     

Bipyridine‐Assisted Assembly of Au Nanoparticles on Cu Nanowires To Enhance the Electrochemical Reduction of CO2

We report a new strategy to prepare a composite catalyst for highly efficient electrochemical CO₂ reduction reaction (CO₂RR). The composite catalyst is made by anchoring Au nanoparticles on Cu nanowires via 4,4′‐bipyridine (bipy). The Au‐bipy‐Cu composite catalyzes the CO₂RR in 0.1 m KHCO₃ with a total Faradaic efficiency (FE) reaching 90.6 % at ?0.9 V to provide C‐products, among which CH₃CHO (25 % FE) dominates the liquid product (HCOO^?, CH₃CHO, and CH₃COO^?) distribution (75 %). The enhanced CO₂RR catalysis demonstrated by Au‐bipy‐Cu originates from its synergistic Au (CO₂ to CO) and Cu (CO to C‐products) catalysis which is further promoted by bipy. The Au‐bipy‐Cu composite represents a new catalyst system for effective CO₂RR conversion to C‐products.     

Overall Carbon-neutral Electrochemical Reduction of CO2 in Molten Salts using a Liquid Metal Sn Cathode

An overall carbon-neutral CO₂ electroreduction requires enhanced conversion efficiency and intensified functionality of CO₂-derived products to balance the carbon footprint from CO₂ electroreduction against fixed CO₂. A liquid Sn cathode is herein introduced into electrochemical reduction of CO₂ in molten salts to fabricate core–shell Sn−C spheres (Sn@C). An in situ generated Li₂SnO₃/C directs a self-template formation of Sn@C. Benefitting from the accelerated reaction kinetics from the liquid Sn cathode and the core–shell structure of Sn@C, a CO₂-fixation current efficiency higher than 84 % and a high reversible lithium-storage capacity of Sn@C are achieved. The versatility of this strategy is demonstrated by other low melting point metals, such as Zn and Bi. This process integrates energy-efficient CO₂ conversion and template-free fabrication of value-added metal-carbon, achieving an overall carbon-neutral electrochemical reduction of CO₂.     

Computational modeling of environmental plutonyl mono-, di- and tricarbonate complexes with Ca counterions: Structures and spectra: , PuO2(CO3)2Ca, and PuO2(CO3)3Ca3

We have computed the structures, and select vibrational spectra, electron density and molecular orbital contour plots of plutonium(VI) complexes of environmental importance such as [PuO₂(CO₃)₂]²⁻ and [PuO₂(CO₃)₃]⁴⁻. We show that Ca²⁺ is efficacious in gas-phase modeling of electronic and spectroscopic properties of multiply charged plutonyl di and tricarbonate anions through complexes such as PuO₂(CO₃)₂Ca and [PuO₂(CO₃)₃Ca₃]²⁺.     

Formation of alloys upon the simultaneous electrochemical deposition of gold and tin from ethylene glycol and aqueous electrolytes

An ethylene glycol (EG) solution containing Au(III) and Sn(IV) compounds, and conditions for the electrochemical deposition of Au–Sn alloy based on AuSn and Au₅Sn intermetallics with total tin content of 30–55 at % are proposed. Fundamental difficulties of the deposition of alloys with high tin content, (including eutectic Au–Sn alloy) from aqueous electrolytes are revealed. It is determined via voltammetry that the simultaneous deposition of gold and tin from aqueous and EG electrolytes proceeds with the depolarization effect of both Au(III) and Sn(IV) as a result of the formation of the alloy, the increase in the rate of tin cathodic reduction being more noticeable in case of EG solution. Formation of SnCl₂EG(H₂O)₂⁺ complex upon the dissolution of SnCl₄ · 5H₂O in glycol, the stability of the composition of tetracyanoaurate ions upon the dissolution of K[Au(CN)₄], and the weakening of intermolecular interactions in EG with small amounts of water were revealed via IR spectroscopy. It is suggested that the depolarization effect is due not only to alloy formation, but also to the formation of SnCl₂EG(H₂O)₂⁺ cations, their association with Au(CN)₄^- anions, and a change in the mechanism of Au(III) and Sn(IV) reduction.     

Dynamic Changes in the Structure,Chemical State and Catalytic Selectivity of Cu Nanocubes during CO2 Electroreduction: Size and Support Effects

In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, chemical state, and reactivity of size‐ and shape‐controlled ligand‐free Cu nanocubes during CO₂ electroreduction (CO₂RR). Dynamic changes in the morphology and composition of Cu cubes supported on carbon were monitored under potential control through electrochemical atomic force microscopy, X‐ray absorption fine‐structure spectroscopy and X‐ray photoelectron spectroscopy. Under reaction conditions, the roughening of the nanocube surface, disappearance of the (100) facets, formation of pores, loss of Cu and reduction of CuO_x species observed were found to lead to a suppression of the selectivity for multi‐carbon products (i.e. C₂H₄ and ethanol) versus CH₄. A comparison with Cu cubes supported on Cu foils revealed an enhanced morphological stability and persistence of Cu^I species under CO₂RR in the former samples. Both factors are held responsible for the higher C₂/C₁ product ratio observed for the Cu cubes/Cu as compared to Cu cubes/C. Our findings highlight the importance of the structure of the active nanocatalyst but also its interaction with the underlying substrate in CO₂RR selectivity.     

Dynamic Changes in the Structure,Chemical State and Catalytic Selectivity of Cu Nanocubes during CO2 Electroreduction: Size and Support Effects

In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, chemical state, and reactivity of size‐ and shape‐controlled ligand‐free Cu nanocubes during CO₂ electroreduction (CO₂RR). Dynamic changes in the morphology and composition of Cu cubes supported on carbon were monitored under potential control through electrochemical atomic force microscopy, X‐ray absorption fine‐structure spectroscopy and X‐ray photoelectron spectroscopy. Under reaction conditions, the roughening of the nanocube surface, disappearance of the (100) facets, formation of pores, loss of Cu and reduction of CuO_x species observed were found to lead to a suppression of the selectivity for multi‐carbon products (i.e. C₂H₄ and ethanol) versus CH₄. A comparison with Cu cubes supported on Cu foils revealed an enhanced morphological stability and persistence of Cu^I species under CO₂RR in the former samples. Both factors are held responsible for the higher C₂/C₁ product ratio observed for the Cu cubes/Cu as compared to Cu cubes/C. Our findings highlight the importance of the structure of the active nanocatalyst but also its interaction with the underlying substrate in CO₂RR selectivity.     

Electrochemical Reduction of Carbon Dioxide to 1-Butanol on Oxide-Derived Copper

The electroreduction of carbon dioxide using renewable electricity is an appealing strategy for the sustainable synthesis of chemicals and fuels. Extensive research has focused on the production of ethylene, ethanol and n-propanol, but more complex C₄ molecules have been scarcely reported. Herein, we report the first direct electroreduction of CO₂ to 1-butanol in alkaline electrolyte on Cu gas diffusion electrodes (Faradaic efficiency=0.056 %, j_1-Butanol=−0.080 mA cm⁻² at −0.48 V vs. RHE) and elucidate its formation mechanism. Electrolysis of possible molecular intermediates, coupled with density functional theory, led us to propose that CO₂ first electroreduces to acetaldehyde-a key C₂ intermediate to 1-butanol. Acetaldehyde then undergoes a base-catalyzed aldol condensation to give crotonaldehyde via electrochemical promotion by the catalyst surface. Crotonaldehyde is subsequently electroreduced to butanal, and then to 1-butanol. In a broad context, our results point to the relevance of coupling chemical and electrochemical processes for the synthesis of higher molecular weight products from CO₂.     

Anreicherung und spektrochemische Bestimmung von Spurenelementen in reinsten Thalliumpr?paraten

Zusammenfassung Zur Anreicherung von Spurenelementen aus Lösungen reinster Thalliumpräparate wird die Matrix Thallium als TlJ ausgefällt. Dabei bleiben die Spuren Mg, Zn, Al, Ga, In, Fe, Co, Ni, Mn, Sn, La, Ce, Th und U quantitativ in Lösung, während Bi, Cu, Pb und Cd sowie die Edelmetalle Ag, Hg, Pd, Au und Pt vom Niederschlag mitgerissen werden. Die Adsorption der für die Reinheitsprüfung des Thalliums wichtigen Elemente Bi, Cu, Pb und Cd kann verhindert werden, wenn sie mit Hilfe von ÄDTA in Komplexanionen übergeführt werden. Als Fällungsmittel wird NaJ verwendet. Zur spektrochemischen Bestimmung werden Pb, Cd, Bi, Ni, Co und In als DDTC-Komplexe mit Chloroform extrahiert. Nach Zusatz einer Mischung von Lithiumcarbonat-Kohle und den Referenzelementen Sn und Pd wird der Eindampfrückstand im Gleichstrombogen analysiert. Cu und Fe werden photometrisch bestimmt.

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Enrichment and spectrochemical determination of trace elements in high-purity thallium preparations

For the enrichment of trace elements in solutions of high-purity thallium samples, thallium is precipitated in form of TlI. In this process the noble metals Ag, Hg, Pd, Au, Pt and also Bi, Cu, Pb and Cd will be co-precipitated, whereas many other elements (Mg, Zn, Al, Ga, In, Fe, Co, Ni, Mn, Sn, La, Ce, Th, U) will remain completely in solution. The adsorption of the four elements Bi, Cu, Pb, Cd, which are important for the purity control of thallium compounds, can be prevented, if they are complexed with EDTA to form complex anions. The precipitating reagent is NaI. For the spectrochemical determination of Pb, Cd, Bi, Ni, Co, and In, the trace elements are extracted as DDTC complexes with chloroform. After the addition of a mixture of Li₂CO₃, carbon, and the reference elements Sn and Pd, the sample is analysed, using the d.c. arc. Cu and Fe are determined spectrophotometrically.

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Wir danken dem Fonds der chemischen Industrie für die finanzielle Unterstützung dieser Arbeit.