Opening Direct Electrochemical Fischer-Tropsch Synthesis Path by Interfacial Engineering of Cu Electrode with P-Block Elements.

The electrochemical synthesis of syngas (CO and H2) has garnered considerable attention in the context of Fischer-Tropsch (FT) synthesis employing thermal catalysts. Nonetheless, the need for a novel, cost-effective technique persists. In this investigation, we introduce a direct electrochemical (dEC) approach for FT synthesis that functions under ambient conditions by utilizing a p-block element (Sn and In) overlaid Cu electrode. Surface *CO and H* species were obtained in an electrolytic medium through the CO2 + H+ + e- → HOOCad → *CO (or direct CO adsorption) and H+ + e- → H* reactions, respectively. We have observed C2-7 long-chain hydrocarbons with a CnH2n+2/CnH2n ratio of 1-3, and this observation can be explained through the process of C-C coupling chain growth of the conventional FT synthesis, based on the linearity of the Anderson-Schulz-Flory equation plots. Thick Sn and In overlayers resulted in the dominant production of formate, while CO and C2H4 production were found to be proportional and inversely correlated to H2, C2H6, and C3-7 hydrocarbon production. The EC CO2/CO reduction used in dEC FT synthesis offers valuable insights into the mechanism of C2+ production and holds promise as an eco-friendly approach to producing long-chain hydrocarbons for energy and environmental purposes.

New reaction path for long-chain hydrocarbons by electrochemical CO2 and CO reduction over Au/stainless steel.

The Fischer-Tropsch (F-T) synthesis is recognized for its ability to produce long-chain hydrocarbons. In this study, we aimed to replicate F-T synthesis using electrochemical CO2 reduction and CO reduction reactions on a stainless steel (SS) support with a gold (Au) overlayer. Under CO2-saturated conditions, the presence of Au on the SS surface led to the formation of CH4 and a range of hydrocarbons (CnH2n and CnH2n+2, n = 2-7), while bare SS primarily produced hydrogen. The Au(10 nm)/SS exhibited the highest hydrocarbon production in CO2-saturated phosphate, indicating a synergistic effect at the Au-SS interface. In CO-saturated conditions, bare SS also produced long-chain hydrocarbons, but increasing Au thickness resulted in decreased production due to poor CO adsorption. Hydrocarbons were formed through both direct and indirect CO adsorption pathways. Anderson-Schulz-Flory analysis confirmed surface CO hydrogenation and C-C coupling polymerization following conventional F-T synthesis. The C2 hydrocarbons exhibited distinct behavior compared to C3-5 hydrocarbons, suggesting different reaction pathways. Despite low reduction product levels, our EC method successfully replicated F-T synthesis using the Au/SS electrode, providing valuable insights into C-C coupling mechanisms and electrochemical production of long-chain hydrocarbons. Depth-profiling X-ray photoelectron spectroscopy revealed significant changes in surface elemental compositions before and after EC reduction.

Interface Engineered V-Zn Hybrids: Electrocatalytic and Photocatalytic CO2 Reductions.

V-Zn hybrids have widely been used as catalyst materials in the environment and as energy. Herein, V-Zn hybrid electrodes were prepared by the hydrothermal and sputter-deposition methods using a Zn foil support. Their electrocatalytic CO2 reduction (EC CO2 RR) performances were tested under various applied potentials, different electrolytes, and concentrations before and after thermal treatment of the demonstrated electrode. Gas and liquid products were confirmed by gas chromatography and nuclear magnetic resonance spectroscopy, respectively. For V-Zn electrode by hydrothermal method produced mainly syngas (CO and H2) with tunable ratio by varying applied potential. Minor products include CH4, C2H4, and C2H6. A liquid product of formate showed a Faradaic efficiency (FE) of 2%. EC CO2 RR efficiency for CO, CH4, and formate was best in 0.2 M KHCO3 electrolyte condition. CO and formate were further increased by photoirradiation and Nafion-treated electrode. Formate and CH4 productions were significantly increased by thermal treatment of the V-Zn electrode. CO production was diminished for the V-Zn electrode by sputter deposition but was recovered by thermal treatment. Photocatalytic CO2 RR was tested to find that RR products include CH3OH, CO, CH4, C2H4, and C2H6. Interestingly long-chain hydrocarbons (CnH2n and CnH2n+2, where n = 3-6) were first observed under mild conditions. The long-chain formation was understood by Fisher-Tropsch (F-T) synthesis. Alkenes were observed to be more produced than alkanes unlike in the conventional F-T synthesis. The present new findings provide useful clues for the development of hybrid electro-and photo-catalysts tested under various experimental conditions in energy and environment.

Photoelectrochemical CO2 Reduction Products Over Sandwiched Hybrid Ga2O3:ZnO/Indium/ZnO Nanorods.

Recycled valuable energy production by the electrochemical CO2 reduction method has explosively researched using countless amounts of developed electrocatalysts. Herein, we have developed hybrid sandwiched Ga2O3:ZnO/indium/ZnO nanorods (GZO/In/ZnONR) and tested their photoelectrocatalytic CO2 reduction performances. Gas chromatography and nuclear magnetic spectroscopy were employed to examine gas and liquid CO2 reduction products, respectively. Major products were observed to be CO, H2, and formate whose Faradaic efficiencies were highly dependent on the relative amounts of overlayer GZO and In spacer, as well as applied potential and light irradiation. Overall, the present study provides a new strategy of controlling CO2 reduction products by developing a sandwiched hybrid catalyst system for energy and environment.

Photocatalytic and Electrocatalytic Properties of Cu-Loaded ZIF-67-Derivatized Bean Sprout-Like Co-TiO2/Ti Nanostructures.

ZIF-derivatized catalysts have shown high potential in catalysis. Herein, bean sprout-like Co-TiO2/Ti nanostructures were first synthesized by thermal treatment at 800 °C under Ar-flow conditions using sacrificial ZIF-67 templated on Ti sheets. It was observed that ZIF-67 on Ti sheets started to thermally decompose at around 350 °C and was converted to the cubic phase Co3O4. The head of the bean sprout structure was observed to be Co3O4, while the stem showed a crystal structure of rutile TiO2 grown from the metallic Ti support. Cu sputter-deposited Co-TiO2/Ti nanostructures were also prepared for photocatalytic and electrocatalytic CO2 reduction performances, as well as electrochemical oxygen reaction (OER). Gas chromatography results after photocatalytic CO2 reduction showed that CH3OH, CO and CH4 were produced as major products with the highest MeOH selectivity of 64% and minor C2 compounds of C2H2, C2H4 and C2H6. For electrocatalytic CO2 reduction, CO, CH4 and C2H4 were meaningfully detected, but H2 was dominantly produced. The amounts were observed to be dependent on the Cu deposition amount. Electrochemical OER performances in 0.1 M KOH electrolyte exhibited onset overpotentials of 330-430 mV (vs. RHE) and Tafel slopes of 117-134 mV/dec that were dependent on Cu-loading thickness. The present unique results provide useful information for synthesis of bean sprout-like Co-TiO2/Ti hybrid nanostructures and their applications to CO2 reduction and electrochemical water splitting in energy and environmental fields.

Electrochemical Ce(III)/Ce(IV) Redox Behavior and Ce Oxide Nanostructure Recovery over Thio-Terpyridine-Functionalized Au/Carbon Paper Electrodes.

Understanding the electrochemical behaviors of Ce(III)/Ce(IV) ions is essential for better treatment, separation, and recycling of lanthanide (Ln) and actinide (An) elements. Herein, electrochemical redox behavior and interconversion of Ce(III)/Ce(IV) ions and their recoveries were demonstrated over newly developed thio-terpyridine-functionalized Au-modified carbon paper electrodes in acidic and neutral electrolytes. Cyclic voltammetry and amperometry were performed for the electrodes with and without thio-terpyridine functionalization. Ce oxide nanostructure recovery was successfully conducted by amperometry, and the electrodeposited nanostructured Ce materials were fully characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction crystallography, and X-ray photoelectron spectroscopy. Geometry optimization and the electronic energy state calculations were conducted by density functional theory at the B3LYP/GENECP level for the complexes of Ce(III) and Ce(IV) ions with the thio-terpyridine in an aqueous state. The present unique results provide valuable information on understanding redox behaviors of Ln and An ions for their recycling and treatment processes.

Electrochemical Recovery and Behaviors of Rare Earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) Ions on Ni Sheets.

The electrochemical behaviors of rare earth (RE) ions have extensively been studied because of their high potential applications to the reprocessing of used nuclear fuels and RE-containing materials. In the present study, we fully investigated the electrochemical behaviors of RE(III) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) ions over a Ni sheet electrode in 0.1 M NaClO4 electrolyte solution by cyclic voltammetry between +0.5 and -1.5 V (vs. Ag/AgCl). Amperometry electrodeposition experiments were performed between -1.2 and -0.9 V to recover RE elements over the Ni sheet. The successfully RE-recovered Ni sheets were fully characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The newly reported recovery data for RE(III) ions over a metal electrode provide valuable information on the development of the treatment methods of RE elements.

Photocatalytic CO2 Reduction and Electrocatalytic H2 Evolution over Pt(0,II,IV)-Loaded Oxidized Ti Sheets.

Energy recycling and production using abundant atmospheric CO2 and H2O have increasingly attracted attention for solving energy and environmental problems. Herein, Pt-loaded Ti sheets were prepared by sputter-deposition and Pt4+-reduction methods, and their catalytic activities on both photocatalytic CO2 reduction and electrochemical hydrogen evolution were fully demonstrated. The surface chemical states were completely examined by X-ray photoelectron spectroscopy before and after CO2 reduction. Gas chromatography confirmed that CO, CH4, and CH3OH were commonly produced as CO2 reduction products with total yields up to 87.3, 26.9, and 88.0 µmol/mol, respectively for 700 °C-annealed Ti under UVC irradiation for 13 h. Pt-loading commonly negated the CO2 reduction yields, but CH4 selectivity was increased. Electrochemical hydrogen evolution reaction (HER) activity showed the highest activity for sputter-deposited Pt on 400 °C-annealed Ti with a HER current density of 10.5 mA/cm2 at -0.5 V (vs. Ag/AgCl). The activities of CO2 reduction and HER were found to be significantly dependent on both the nature of Ti support and the oxidation states (0,II,IV) of overlayer Pt. The present result could provide valuable information for designing efficient Pt/Ti-based CO2 recycle photocatalysts and electrochemical hydrogen production catalysts.

Pt Deposits on Bi/Pt NP Catalyst for Formic Acid Oxidation: Catalytic Enhancement and Longer Lifetime.

This work presents an improvement in the activity and catalytic lifetime of Pt deposits on Bi-modified Pt nanoparticles (Bi/Pt NP) toward formic acid oxidation (FAO). Using an irreversible adsorption method, Bi was deposited on Pt NP to form Bi/Pt NP and sequentially Pt was deposited on Bi/Pt NP to form Pt/Bi/Pt NP. Voltammetric studies of Pt NP, Bi/Pt NP, and Pt/Bi/Pt NPs supported that Pt deposits of Pt/Bi/Pt NPs provided quite a unique behavior: simultaneous surface oxidation of deposited Pt and Bi and significant resistance to the oxidative removal of Bi. Furthermore, combined spectroscopic investigations revealed that the concentration of the employed Pt precursor ion solution determined the amount of deposited Pt from ∼0.2 to ∼0.4 in coverage. The best Pt/Bi/Pt NP catalyst with a Pt coverage of ∼0.25 enhanced the dehydrogenation processes below ∼0.4 V by a factor of more than 2 and increased the FAO current at ∼0.8 V roughly by 15 times, referring to those of Bi/Pt NP. The lifetime measurement works revealed that after the 1000th voltammetric cycle to 0.4 V, the FAO currents of Pt/Bi/Pt NPs were 2 and 4 times higher than those of Bi/Pt NP and Pt NP, respectively. The Pt deposits on Bi/Pt NP were concluded to play two roles in FAO: the promotion of FAO processes to increase the activity and the retardation of Bi oxidative removal to maintain the activity much longer.

Photoluminescence imaging of europium (III)-doped γ-Al2 O3 nanofiber structures.

Aluminium oxide (Al2 O3 ) has widely been used for catalysts, insulators, and composite materials for diverse applications. Herein, we demonstrated if γ-Al2 O3 was useful as a luminescence support material for europium (Eu) (III) activator ion. The hydrothermal method and post-thermal treatment at 800°C were employed to synthesize Eu(III)-doped γ-Al2 O3 nanofibre structures. Luminescence characteristics of Eu(III) ions in Al2 O3 matrix were fully understood by taking 2D and 3D-photoluminescence imaging profiles. Various sharp emissions between 580 to 720 nm were assigned to the 5 D0 →7 FJ (J = 0, 1, 2, 3, 4) transitions of Eu(III) activators. On the basis of X-ray diffraction crystallography, Auger elemental mapping and the asymmetry ratio, Eu(III) ions were found to be well doped into the γ-Al2 O3 matrix at a low (1 mol%) doping level. A broad emission at 460 nm was substantially increased upon higher (2 mol%) Eu(III) doping due to defect creation. The first 3D photoluminescence imaging profiles highlight detailed understanding of emission characteristics of Eu(III) ions in Al oxide-based phosphor materials and their potential applications.

Solution phase post-modification of a trimesic acid network on Au(111) with Zn(2+) ions.

Solution phase post-modification of a trimesic acid (TMA) network on Au(111) with Zn(2+) ions was found to induce transformation of a bar-featured scanning tunneling microscopy image of (5√3 × 5√3) to a chevron-pair image of (10√3 × 10√3). Voltammetric determination of Zn coverage in the modified TMA network supports the fact that the chevron feature consists of three TMA molecules combined via two coordination bonds between Zn(2+) ions and carboxylates of TMA.

A highly sensitive quartz crystal microbalance immunosensor based on magnetic bead-supported bienzymes catalyzed mass enhancement strategy.

A highly sensitive quartz crystal microbalance (QCM) immunosensor based on magnetic bead-supported bienzyme catalyzed mass enhanced strategy was developed for the detection of human immunoglobulin G (hIgG) protein. The high sensitive detection was achieved by increasing the deposited mass on the QCM crystal through the enhanced precipitation of 4-chloro-1-naphthol (CN) using higher amounts of horseradish peroxidase (HRP) and glucose oxidase (GOx) bienzymes attached on the magnetic beads (MB). The protein A (PA) and capture antibody (monoclonal anti-human IgG antibody produced in mouse, Ab1)-based QCM probe and the detection antibody (anti-human IgG antibody produced in goat, Ab2)-based MB/HRP/GOx bienzymatic bioconjugates were characterized using scanning electron microscope, transmission electron microscope, cyclic voltammetry, and electrochemical impedance spectroscopy techniques. Under the optimized experimental condition, the linear range and the detection limit of hIgG immunosensor were determined to be 5.0pg/mL-20.0ng/mL and 5.0±0.18pg/mL, respectively. The applicability of the present hIgG immunosensor was examined in hIgG spiked human serum samples and excellent recoveries of hIgG were obtained.

Formation of single-layered Pt islands on Au(111) using irreversible adsorption of Pt and selective adsorption of CO to Pt.

This communication compares two different multiple deposition routes of Pt on Au(111), using irreversible adsorption of Pt precursor ions and selective adsorption of CO. A scanning tunneling microscopy study revealed that the conventional route, not utilizing CO, produced multiple-layered Pt cluster islands, while the CO route, employing CO, formed single-layered Pt islands exclusively. The role of CO selectively adsorbed on pre-existing Pt islands was to prevent additional irreversible adsorption of Pt precursor ions onto Pt islands. Cyclic voltammetric works disclosed that the CO and hydrogen coverages on single-layered Pt islands were higher than those on multiple-layered ones, and that the Pt islands on Au were more effective in adsorbing CO than hydrogen.

Increased electrocatalyzed performance through dendrimer-encapsulated gold nanoparticles and carbon nanotube-assisted multiple bienzymatic labels: highly sensitive electrochemical immunosensor for protein detection.

A highly sensitive electrochemical carcinoembryonic antigen (CEA) immunosensor was fabricated by covalently immobilizing a monoclonal CEA antibody (anti-CEA, Ab(1)) and a mediator (thionine, Th) on a gold nanoparticle (AuNP)-encapsulated dendrimer (Den/AuNP). Multiwalled carbon nanotube (MWCNT)-supported secondary antibody (Ab(2))-conjugated multiple bienzymes, glucose oxidase (GOx), and horseradish peroxidase (HRP) (Ab(2)/MWCNT/GOx/HRP) were used as electrochemical labels. The highly sensitive detection was achieved by the increased HRP-electrocatalyzed reduction of hydrogen peroxide, which was locally generated by the enzyme GOx. The immunosensor surface was characterized using electrochemical impedance spectroscopy, atomic force microscopy, and quartz crystal microbalance techniques. The Den/AuNP and Ab(2)/MWCNT/GOx/HRP bioconjugates were characterized using high-resolution transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Cyclic voltammetry and square wave voltammetry techniques were used to monitor the increased electrocatalyzed reduction of hydrogen peroxide by HRP. The linear dynamic range and the detection limit were determined to be 10.0 pg/mL to 50.0 ng/mL and 4.4 ± 0.1 pg/mL, respectively. The validity of the immunosensor response was tested in various CEA-spiked human serum samples, and the results were compared to those of an enzyme-linked immunosorbent assay method.

Amplified electrochemical detection of a cancer biomarker by enhanced precipitation using horseradish peroxidase attached on carbon nanotubes.

An electrochemical nanoimmunosensor based on multiwall carbon nanotubes (MWCNTs)/gold nanoparticles (AuNPs) was developed for the amplified detection of prostate specific antigen (PSA). The amplified detection was achieved by the enhanced precipitation of 4-chloro-1-naphthol (CN) using a higher number of horseradish peroxidase (HRP) molecules attached on MWCNTs. The PSA nanoimmunosensor was fabricated by immobilizing a monoclonal anti-PSA antibody (anti-PSA) on the AuNP-attached thiolated MWCNT on a gold electrode. The sensor surface was characterized using scanning electron microscope, transmission electron microscope, quartz crystal microbalance, and electrochemical techniques. Cyclic and square wave voltammetric techniques were used to monitor the enhanced precipitation of CN that accumulated on the electrode surface and subsequent decrement in the electrode surface area by monitoring the reduction process of the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) redox couple. Under the optimized experimental condition, the linear range and the detection limit of PSA immunosensor were determined to be 1.0 pg/mL to 10.0 ng/mL and 0.40 ± 0.03 pg/mL, respectively. The validity of the proposed method was compared with an enzyme-linked immunosorbent assay method in various PSA spiked human serum samples.

Structure and electrochemical applications of boron-doped graphitized carbon nanofibers.

Boron-doped graphitized carbon nanofibers (CNFs) were prepared by optimizing CNFs preparation, surface treatment, graphitization and boron-added graphitization. The interlayer spacing (d002) of the boron-doped graphitized CNFs reached 3.356 Å, similar to that of single-crystal graphite. Special platelet CNFs (PCNFs), for which d002 is less than 3.400 Å, were selected for further heat treatment. The first heat treatment of PCNFs at 2800 °C yielded a d002 between 3.357 and 3.365 Å. Successive nitric acid treatment and a second heat treatment with boric acid reduced d002 to 3.356 Å. The resulting boron-doped PCNFs exhibited a high discharge capacity of 338 mAh g⁻¹ between 0 and 0.5 V versus Li/Li⁺ and 368 mAh g⁻¹ between 0 and 1.5 V versus Li/Li⁺. The first-cycle Coulombic efficiency was also enhanced to 71-80%. Such capacity is comparable to that of natural graphite under the same charge/discharge conditions. The boron-doped PCNFs also exhibited improved rate performance with twice the capacity of boron-doped natural graphite at a discharge rate of 5 C.

Adsorptive behavior of dimethylglyoxime on Au(111).

Dimethylglyoxime (DMG) adsorbed on Au(111) was investigated using electrochemical scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). STM experiments revealed three different structures of adsorbed DMG at open circuit potential (~0.07 V versus Ag/AgCl): (2√3×2√3)R30°-α, (2√3×4√3)R30°-ß, and (2√3×4√3)R30°-γ. The coverage of adsorbed DMG obtained using XPS was 0.33. A combination of structural and quantitative information identified the adsorbed DMG as an anionic tetramer, held together by intermolecular hydrogen bonding and arrayed in three ordered patterns. Domains of adsorbed DMG underwent phase transitions between the observed structures, most likely due to the influence of the STM tip. However, a significant correlation between the observed structures and the imaging conditions was not found. The ordered layers existed only at open circuit potential as evidenced by their disappearance when the potential was shifted to 0.2 or -0.15 V. The ordered layers were also removed by immersion in a solution of Ni(2+), implying that the adsorbed DMG was converted to a soluble dimer complex with the Ni(2+) ion. This particular observation is discussed in terms of the rigidity of the organic network.

Preoxidation of CO on Os-modified Pt(111): a comparison with Ru-modified Pt(111).

The variation in CO adsorption structures during the preoxidation of CO on Os-modified Pt(111) (Pt(111)/Os) was investigated using cyclic voltammetry and electrochemical scanning tunneling microscopy. The spontaneous deposition of Os on Pt(111) resulted in randomly scattered islands with a coverage range of 0.13-0.54. During preoxidation on Pt(111)/Os, a phase transition from (2 × 2)-α to (√19 × âˆš19) via the transient structures of (2 × 2)-ß and (1 × 1) took place as on unmodified Pt(111). As the amount of Os increased, however, the transient structures of (2 × 2)-ß and (1 × 1) appeared at lower potentials with higher populations. When the population of the transient structures was greater than 50%, an oxidative CO stripping process took place to the structure of (√19 × âˆš19), completing the preoxidation. These observations strongly support the idea that the presence of Os increases the mobility of adsorbed CO by electronic modification of the Pt(111) surface (electronic effect). In addition, the results obtained with Pt(111)/Os were compared with those of Pt(111)/Ru.

Selective adsorption of dithiolate-modified multi-wall carbon nanotubes onto alkanethiol self-assembled monolayers on Au(111).

Dithiolate-modified multi-wall carbon nanotubes (MWCNTs) adsorb selectively on the self-assembled monolayers (SAMs) of alkanethiols on a Au surface: the long dithiolates attached to the MWCNTs anchor the massive MWCNTs onto the Au surface by replacing the shorter thiolates of SAMs.

Modification of Au nanoparticles dispersed on carbon support using spontaneous deposition of Pt toward formic acid oxidation.

This work presents formic acid oxidation on Pt deposits on Au nanoparticles dispersed on Vulcan XC-72R. The Pt deposits were produced using spontaneous deposition method contacting the Au nanoparticles with solutions containing Pt complex ions in various concentrations. The Pt deposits were characterized using CO stripping coulometry, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. When the Pt concentration is 10(-5)-10(-4) M, the Pt deposits are nanoislands of monatomic height. In the concentration range of 10(-4)-10(-3) M, the Pt deposits are most likely two-layer-thick nanofeatures. As Pt concentration increases further, the deposits become wider and thicker. Voltammetric behavior of Pt deposits reveals that on Pt deposits, dehydrogenation path is activated at the expense of poison-forming dehydration path. Furthermore, chronoamperometric measurement of the catalytic activity of Pt deposits supports that the two-layer-thick Pt deposits are most efficient in formic acid oxidation among the studied Pt deposits on Au nanoparticles. The enhancement factor of the particular Pt deposits is 2 in terms of turnover frequency, compared with a commercial Pt catalyst. Details are discussed in conjunction with Pt deposits on Au(111).