Electrochemical Synthesis Research Articles

Regulating Interfacial Microenvironment in Aqueous Electrolyte via a N2 Filtering Membrane for Efficient Electrochemical Ammonia Synthesis.

Electrochemical synthesis of ammonia (NH3) in aqueous electrolyte has long been suffered from poor nitrogen (N2) supply owing to its low solubility and sluggish diffusion kinetics. Therefore, creating a N2 rich microenvironment around catalyst surface may potentially improve the efficiency of nitrogen reduction reaction (NRR). Herein, a delicately designed N2 filtering membrane consisted of polydimethylsiloxane is covered on catalyst surface via superspreading. Because this membrane let the dissolved N2 molecules be accessible to the catalyst but block excess water, the designed N2 rich microenvironment over catalyst leads to an optimized Faradaic efficiency of 39.4% and an NH3 yield rate of 109.2µgh-1mg-1, which is superior to those of the most report metal-based catalysts for electrochemical NRR. This study offers alternative strategy for enhancing NRR performance.

High yield electrosynthesis of oxygenates from CO using a relay Cu-Ag co-catalyst system

As a sustainable alternative to fossil fuel-based manufacture of bulk oxygenates, electrochemical synthesis using CO and H2O as raw materials at ambient conditions offers immense appeal. However, the upscaling of the electrosynthesis of oxygenates encounters kinetic bottlenecks arising from the competing hydrogen evolution reaction with the selective production of ethylene. Herein, a catalytic relay system that can perform in tandem CO capture, activation, intermediate transfer and enrichment on a Cu-Ag composite catalyst is used for attaining high yield CO-to-oxygenates electrosynthesis at high current densities. The composite catalyst Cu/30Ag (molar ratio of Cu to Ag is 7:3) enables high efficiency CO-to-oxygenates conversion, attaining a maximum partial current density for oxygenates of 800 mA cm−2 at an applied current density of 1200 mA cm−2, and with 67 % selectivity. The ability to finely control the production of ethylene and oxygenates highlights the principle of efficient catalyst design based on the relay mechanism.

Influence of Water Hardness and Complexing Agents on Electrochemical Hydrogen Peroxide Generation.

Recently, many studies have been published regarding electrochemical oxygen reduction reaction for generating hydrogen peroxide (H2O2) using gas diffusion electrodes (GDEs) for various applications. Sodium salts solved in deionized water were usually used as supporting electrolytes. In technical applications, however, tap water-based electrolytes with hardeners are particularly relevant and have only been considered in a few studies to date. In this work, we investigated the influence of hardeners on H2O2-generation at 150mAcm‑2 and were able to show that scaling occurs predominantly on the GDE surface and not in its pore structure. With the novel method in electrochemical synthesis by using complexing agents to bind hardeners, we were able to significantly reduce the scaling. Even after 10h of operation, the reactor still achieves a faradaic efficiency (FE) of above 70% (> 67 mg h-1 cm-2), comparable to the experiments without hardeners and complexing agents in the electrolyte. Furthermore, we demonstrate that the complexing agents are not electrochemically converted at the carbon-based GDE and behave inertly. If the cell is operated with complexing agents and rinsed with acidic liquid (anolyte) between batches, scaling can be completely avoided.

A Review of the Effect of Different Electrolytes on the Synthesis of Graphene Sheets by Electrochemical Exfoliation

Graphene oxide (GO) possess some excellent properties that fulfil various applications. Hummers’ method has been used in GO synthesis for years but some issues such as high-cost GO synthesis, the use of toxic chemicals and low yield of GO are still remains and concerned. In addition, this method spends very long time to be completed and subjected to thorough cleaning process to remove toxic chemicals. On the other hand, the electrochemical method saves time, has no explosion risk, releases no toxic gases, and keep safe environmental. The demand of GO supply is crucial particularly important in applications such as energy storage in automobiles thus, a large scale and cheap production of GO is needed. It is reported that the electrochemical synthesis of GO has more benefits such as rapid synthesis, low cost and environmentally friendly than Hummers’ method, therefore, the impact of different electrolytes is important to be studied. Herein, various research works about the electrochemical synthesis of GO are reviewed, precisely involving the anodic exfoliation of graphite, exfoliation mechanism and effects of exfoliation parameters.

Surface Reconstruction for Selective Oxidation of Tetrahydroisoquinoline.

Integration of hydrogen evolution with the oxidation of organic substances in one electrochemical system is highly desirable. However, achieving selective oxidation of organic substances in the integrated system is still highly challenging. In this study, a phosphorylated NiMoO4 nanoneedle-like array was designed as the catalytic active electrode for the integration of highly selective electrochemical dehydrogenation of tetrahydroisoquinolines (THIQs) with hydrogen production. The leaching of anions, including MoO42- and PO43-, facilitates the reconstruction of the catalyst. As a result, nickel oxyhydroxides with the doping of PO43- and richness of defects are in situ formed. In situ Raman and density functional theory calculations have shown that the high catalytic activity is attributed to the in situ formed PO43- involved NiOOH substance. In the dehydrogenation process, the involved C-H bond but not the N-H bond is first destroyed. A two-electrode system was then fabricated with the optimized electrode that shows a benchmark current density of 10 mA cm-2 at 1.783 V, providing a yield of 70% for dihydroisoquinolines. A robust stability was also shown for this integrated electrochemical system. The understanding of the reconstruction behavior and the achievement of selective dehydrogenation will provide some hints for electrochemical synthesis.

Highly Selective Electrochemical Baeyer-Villiger Oxidation through Oxygen Atom Transfer from Water.

The Baeyer-Villiger oxidation of ketones is a crucial oxygen atom transfer (OAT) process used for ester production. Traditionally, Baeyer-Villiger oxidation is accomplished by thermally oxidizing the OAT from stoichiometric peroxides, which are often difficult to handle. Electrochemical methods hold promise for breaking the limitation of using water as the oxygen atom source. Nevertheless, existing demonstrations of electrochemical Baeyer-Villiger oxidation face the challenges of low selectivity. We report in this study a strategy to overcome this challenge. By employing a well-known water oxidation catalyst, Fe2O3, we achieved nearly perfect selectivity for the electrochemical Baeyer-Villiger oxidation of cyclohexanone. Mechanistic studies suggest that it is essential to produce surface hydroperoxo intermediates (M-OOH, where M represents a metal center) that promote the nucleophilic attack on ketone substrates. By confining the reactions to the catalyst surfaces, competing reactions (e.g., dehydrogenation, carboxylic acid cation rearrangements, and hydroxylation) are greatly limited, thereby offering high selectivity. The surface-initiated nature of the reaction is confirmed by kinetic studies and spectroelectrochemical characterizations. This discovery adds nucleophilic oxidation to the toolbox of electrochemical organic synthesis.

High Potential Electrochemical Synthesis of Thermally Reduced Graphene Nanomaterial

In this study, we provide electrochemical techniques for synthesizing thermally reduced graphene nanomaterial that have high potential, low defects, cost-effectiveness, and ecological sustainability. The electrochemical exfoliation is carried out by employing a 195 W DC (voltage = 60[Formula: see text]V and current = 3.25 A) power source at a maximum electrolyte temperature of about 92.5∘C within the aqueous suspension of 2[Formula: see text]M of sulfuric acid (H2SO[Formula: see text]. Thereafter, the synthesized nanomaterial was treated in the weak piranha [combination of sulfuric acid and hydrogen peroxide (H2O[Formula: see text]] solution using an electrochemical technique inside the water bath sonicator at 80∘C. X-ray diffraction (XRD) analysis shows the peak of diffraction to the (002) plane of the reduced graphene oxide (RGO) samples emerges at around 2[Formula: see text] and 26.56∘ with an interplanar distance of 3.40 Å and 3.54 Å. According to the XRD data, after the high-temperature thermal reduction phase, the structure of the crystals and interplanar separation were recovered. The size of the crystallite of RGO produced under H2SO4 conditions was discovered to be greater than the crystallite size of graphene oxide produced under piranha solution conditions. The Raman analysis results show that the degree of disorder of the graphene synthesized within the H2O2 was higher than in comparison to the graphene synthesized in H2SO4. Field emission scanning electron microscopy (FE-SEM) results show that graphene synthesized in the presence of H2O2 has a thin and porous microstructure in comparison to H2SO4 with no significant effect on the presence of the availability of the C/O ratio. The atomic force microscopy (AFM) analysis indicates that the surface roughness of the graphene synthesized in the H2O2 was higher than that of the H2SO4. The Fourier transform infrared spectroscopy (FT-IR spectroscopy) analytical results show that the majority of the functional groups have been eliminated within the samples.

Spatial decoupling of bromide-mediated process boosts propylene oxide electrosynthesis

The electrochemical synthesis of propylene oxide is far from practical application due to the limited performance (including activity, stability, and selectivity). In this work, we spatially decouple the bromide-mediated process to avoid direct contact between the anode and propylene, where bromine is generated at the anode and then transferred into an independent reactor to react with propylene. This strategy effectively prevents the side reactions and eliminates the interference to stability caused by massive alkene input and vigorously stirred electrolytes. As expected, the selectivity for propylene oxide reaches above 99.9% with a remarkable Faradaic efficiency of 91% and stability of 750-h (>30 days). When the electrode area is scaled up to 25 cm2, 262 g of pure propylene oxide is obtained after 50-h continuous electrolysis at 6.25 A. These findings demonstrate that the electrochemical bromohydrin route represents a viable alternative for the manufacture of epoxides.

Electrochemical de-alloying synthesis of porous AuTiCeOx/NC cyclohexene hydrogenation SPE membrane electrode by combination method

Electrochemical de-alloying synthesis of porous AuTiCeOx/NC cyclohexene hydrogenation SPE membrane electrode by combination method

Electrochemical Synthesis of Hollow Nanoparticles via Anodic Transformation of Metastable Core-Shell Precursors.

Recent advances in electrosynthesis of nanomaterials expanded structural and compositional variations accessible by the electrochemical method; however, reliably synthesizable morphological variety fall shy of that available by conventional solvothermal synthesis. In this communication, electrochemical preparation of surfactant-free hollow nanoparticles is demonstrated. By anodic conversion of core-shell precursors with metastable cores, hollowed nickel nanoparticles with uniform dimensions were synthesized and characterized. Implementation of TEM grids as the working electrodes, identical location tracking of the morphological evolution of single particles to anodic stimulus has been demonstrated. The synthesized nanoparticles were employed as catalysts for the alkaline hydrogen evolution reaction and exhibited catalytic rates that compare favorably to the Pt/C benchmark. This marks the first pure electrochemical synthesis of hollow nanoparticles and shall contribute to the structural diversification of electrosynthesized nanomaterials.

A highly sensitive electrochemical sensor for the detection of chloramphenicol based on Ni/Co bimetallic metal-organic frameworks/reduced graphene oxide composites

A highly and simply sensitive electrochemical sensor has been developed for the detection of trace chloramphenicol (CAP) in water based on Ni/Co bimetallic metal–organic frameworks-reduced graphene oxide composites [rGO/NiCo-BTC MOFs (BTC = 1,3,5-benzenetricarboxylicacid)] modified glassy carbon electrode (GCE/rGO/NiCo-BTC MOFs). The bare glassy carbon electrode was initially coated with graphene oxide (GO). Subsequently, the GO was electrochemically reduced to obtain reduced graphene oxide (rGO). NiCo-BTC MOFs was grown on the surface of rGO modified electrode by in-situ electrochemical synthesis method to construct GCE/rGO/NiCo-BTC MOFs. The as-made composites films have been characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Further, different electrochemical techniques were utilized for investigating the electrochemical reduction behaviors of CAP at GCE/rGO/NiCo-BTC MOFs. This composites film modified electrode combines the large surface area and excellent electrical properties of rGO with the good catalytic activity of NiCo-BTC MOFs, resulting in a significant enhancement of the electrochemical signal during the electroreduction of CAP. Under the optimized experimental conditions, the sensor exhibits excellent sensing performance for CAP, with a wider linear dynamic range (0.1 − 100 μM), a lower limit of detection (0.235 μM) (S/N = 3) and a ultra-high sensitivity (33.12 μA·μM−1·cm−2). The tap water spiked with different concentrations of CAP were considered. The recoveries range from 97.79 % to 100.07 %, with relative standard deviations ranging from 3.45 % to 5.40 %. The method has been successfully applied for the determination of CAP in real samples, yielding satisfactory results. With further research and development, electrochemical in-situ synthesis of MOFs composites have the potential to revolutionize the design and performance of electrochemical sensors, holding great promise in the field of electrochemical sensing.

Template-assisted electrodeposition of freestanding antimony, tin, and antimony-tin nanowire arrays from an ionic liquid

AbstractIn the present study, we show the electrochemical synthesis of Sb, Sn, and Sb-Sn nanowire arrays from the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonate ([Py1,4]TfO) via templated-assisted approaches. Commercially available track etched polycarbonate template with a nominal pore diameter of 400 nm was utilized as a template. The nanowires were electrochemically deposited inside the pores of the template; then, a supporting copper layer was electrodeposited on the back side of the template. Subsequently, the template was dissolved with dichloromethane, and the structural morphology of the nanowire structures was explored by high-resolution scanning electron microscopy (SEM) and energy dispersive x-ray (EDX). Freestanding, mechanically stable nanowire arrays of Sb, Sn, and Sb-Sn with an average pore diameter of 400 nm were obtained. The charge/discharge characteristics of the electrodeposited nanowire films were investigated to explore the Li storage capacity of the fabricated electrodes. The results revealed that the electrodeposited nanowire films are promising anode candidates for the future generation of Li-ion batteries. Graphical abstract

Electrochemical Synthesis of Polyaniline for Enhanced Congo Red Removal Efficiency in Wastewater Treatment

Electrochemical Synthesis of Polyaniline for Enhanced Congo Red Removal Efficiency in Wastewater Treatment

Continuous Flow Electrochemical Synthesis of Olivine-Structured NaFePO4 Cathode Material for Sodium-Ion Batteries from Recycle LiFePO4.

To mitigate the environmental impact of the improper disposal of spent LiFePO4 batteries and reduce resource waste, the development of LiFePO4 recycling technologies is of paramount importance. Meanwhile, olivine-structured NaFePO4 in sodium-ion batteries has received great attention, due to its high theoretical specific capacity of 154 mAh g-1 and excellent stability. However, olivine NaFePO4 only can be synthesized from olivine LiFePO4. Accordingly, in this proposal, developing the continuous flow electrochemical solid-liquid reactor-based metal ion insertion technology is to utilize the olivine FePO4, recycled from LiFePO4, and to synthesize NaFePO4. Additionally, by employing I- as the reducing agent, NaFePO4 is successfully synthesized with a discharge-specific capacity of 134 mAh g-1 at 0.1C and a remarkable capacity retention rate of 86.5% after 100 cycles at 0.2C. And the reasons for sodium deficiency in the synthesized NFP are elucidated through first-principles calculations. Furthermore, the kinetics of the solid-solution reaction 2 (Na2/3+βPO4→ Na1-αFePO4) mechanism improve with cycling and are sensitive to temperature. Utilizing a minimal amount of reducing agent in the electrochemical reactor, NaFePO4 synthesis is successfully achieved. This innovative approach offers a new, cost-effective, and environmentally friendly strategy for preparing NaFePO4 from recycling LiFePO4.

Electrochemical synthesis of 2D-silver nanodendrites functionalized with cyclodextrin for SERS-based detection of herbicide MCPA

Surface enhanced Raman spectroscopy (SERS) is a powerful analytical technique that has found application in the trace detection of a wide range of contaminants. In this paper, we report on the fabrication of 2D silver nanodendrites, on silicon chips, synthesized by electrochemical reduction of AgNO3 at microelectrodes. The formation of nanodendrites is tentatively explained in terms of electromigration and diffusion of silver ions. Electrochemical characterization suggests that the nanodendrites do not stay electrically connected to the microelectrode. The substrates show SERS activity with an enhancement factor on the order of 106. Density functional theory simulations were carried out to investigate the suitability of the fabricated substrate for pesticide monitoring. These substrates can be functionalized with cyclodextrin macro molecules to help with the detection of molecules with low affinity with silver surfaces. A proof of concept is demonstrated with the detection of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA).

Electrochemical synthesis of hierarchical porous PbSe film and its infrared photodetection properties

Lead selenide (PbSe) has been extensively studied as an infrared detection material capable of operating at room temperature. In this research, we proposed a simple cyclic voltammetry (CV) electrodeposition of hierarchical porous PbSe on single-layer graphene film. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy were used to evaluate the physical and surface characteristics of porous PbSe films. The porous structure with large surface to volume ratio will enhance the light absorption ability after effectively sensitized in oxygen atmosphere. Furthermore, oxygen-sensitized processes create electron traps at grain boundaries, extending the lifetime of the hole carrier and improving photoconductive sensitivity. At room temperature, the porous PbSe/graphene photodetector exhibit a responsivity of 12.3 A/W, a detectivity of 5.95 * 108 cm Hz1/2W−1 (@1 kHz) at 1.55 µm, and a responsivity of 15.2 A/W, a detectivity of 1.4 * 109 cm Hz1/2W−1(@1 kHz) at 2.7 µm. This work highlights the low cost and effective electrodeposition strategy for constructing hierarchical porous structure with further application in infrared photodetection.

Electrochemical Synthesis of C(sp3)‐Rich Amines by Aminative Carbofunctionalization of Carbonyl Compounds

Alkylamines form the backbone of countless nitrogen‐containing small molecules possessing desirable biological properties. Despite advances in amine synthesis through transition metal catalysis and photoredox chemistry, multicomponent reactions that leverage inexpensive materials to transform abundant chemical feedstocks into three‐dimensional α‐substituted alkylamines bearing complex substitution patterns remain scarce. Here, we report the design of a catalyst‐free electroreductive manifold that merges amines, carbonyl compounds and carbon‐based radical acceptors under ambient conditions without rigorous exclusion of air and moisture. Key to this aminative carbofunctionalization process is the chemoselective generation of nucleophilic α‐amino radical intermediates that readily couple with electrophilic partners, providing straightforward access to architecturally intricate alkylamines and drug‐like scaffolds which are inaccessible by conventional means.

Single-Atom Iron Catalyst as an Advanced Redox Mediator for Anodic Oxidation of Organic Electrosynthesis.

Homogeneous electrocatalysts can indirect oxidate the high overpotential substrates through single-electron transfer on the electrode surface, enabling efficient operation of organic electrosynthesis catalytic cycles. However, the problems of this chemistry still exist such as high dosage, difficult recovery, and low catalytic efficiency. Single-atom catalysts (SACs) exhibit high atom utilization and excellent catalytic activity, hold great promise in addressing the limitations of homogeneous catalysts. In view of this, we have employed Fe-SA@NC as an advanced redox mediator to try to change this situation. Fe-SA@NC was synthesized using an encapsulation-pyrolysis method, and it demonstrated remarkable performance as a redox mediator in a range of reported organic electrosynthesis reactions, and enabling the construction of various C-C/C-X bonds. What's more, Fe-SA@NC demonstrated a great potential in exploring new synthetic method for organic electrosynthesis. We em-ployed it to develop a new electro-oxidative ring-opening transformation of cyclopropyl amides. In this new reaction system, Fe-SA@NC showed good tolerance to drug molecules with complex structures, as well as enabling flow electrochemical syntheses and gram-scale transformations. This work highlights the great potential of SACs in organic electrosynthesis, thereby opening a new avenue in synthetic chemistry.

Single‐Atom Iron Catalyst as an Advanced Redox Mediator for Anodic Oxidation of Organic Electrosynthesis

Homogeneous electrocatalysts can indirect oxidate the high overpotential substrates through single‐electron transfer on the electrode surface, enabling efficient operation of organic electrosynthesis catalytic cycles. However, the problems of this chemistry still exist such as high dosage, difficult recovery, and low catalytic efficiency. Single‐atom catalysts (SACs) exhibit high atom utilization and excellent catalytic activity, hold great promise in addressing the limitations of homogeneous catalysts. In view of this, we have employed Fe‐SA@NC as an advanced redox mediator to try to change this situation. Fe‐SA@NC was synthesized using an encapsulation‐pyrolysis method, and it demonstrated remarkable performance as a redox mediator in a range of reported organic electrosynthesis reactions, and enabling the construction of various C‐C/C‐X bonds. What's more, Fe‐SA@NC demonstrated a great potential in exploring new synthetic method for organic electrosynthesis. We em‐ployed it to develop a new electro‐oxidative ring‐opening transformation of cyclopropyl amides. In this new reaction system, Fe‐SA@NC showed good tolerance to drug molecules with complex structures, as well as enabling flow electrochemical syntheses and gram‐scale transformations. This work highlights the great potential of SACs in organic electrosynthesis, thereby opening a new avenue in synthetic chemistry.

Electrochemical Synthesis of C(sp3)-Rich Amines by Aminative Carbofunctionalization of Carbonyl Compounds.

Alkylamines form the backbone of countless nitrogen-containing small molecules possessing desirable biological properties. Despite advances in amine synthesis through transition metal catalysis and photoredox chemistry, multicomponent reactions that leverage inexpensive materials to transform abundant chemical feedstocks into three-dimensional α-substituted alkylamines bearing complex substitution patterns remain scarce. Here, we report the design of a catalyst-free electroreductive manifold that merges amines, carbonyl compounds and carbon-based radical acceptors under ambient conditions without rigorous exclusion of air and moisture. Key to this aminative carbofunctionalization process is the chemoselective generation of nucleophilic α-amino radical intermediates that readily couple with electrophilic partners, providing straightforward access to architecturally intricate alkylamines and drug-like scaffolds which are inaccessible by conventional means.