Efficient Electrochemical Systems Research Articles

The Role of Alkali Cations on the Selectivity of 5-Hydroxymethylfurfural Electroreduction on Glassy Carbon.

In the past decade, organic electrosynthesis has emerged as an atom- and energy-efficient strategy for harvesting renewable electricity that provides exceptional control over the reaction parameters. A profound and fundamental understanding of electrochemical interfaces becomes imperative to advance the knowledge-based development of electrochemical processes. The major strategy toward an efficient electrochemical system is based on the advancement in material science for electrocatalysis. Studies on the complex interplay among electrode surface, electrolyte, and transformation intermediates have only recently started to emerge. It involves acquiring atomic-scale insights into the electrochemical double layer, for which the identity and concentration of composing ions play a crucial role. In this study, we present how the identity and concentration of alkali cations impact the selectivity of aldehyde functionality electroreduction. As a case-study transformation, we set the electrochemical conversion of 5-hydroxymethylfurfural (HMF), a promising biomass-derived feedstock for the sustainable production of polymer or fuel precursors. Our findings reveal a consistent trend of the selectivity shift towards 2,5-bis(hydroxymethyl)furan (BHMF) as a function of cation size and concentration, rationalized by specific cation adsorption at the glassy carbon (GC), followed by the increase in the electrode surface charge density.

Electrocatalytic removal of phenol from coking wastewater using coal based electrode materials

An efficient electrochemical system for phenol degradation in coking wastewater was established. Wherein the economic homemade coal electrode materials (CEMs) and titanium electrode were used as the work electrodes. The removal rate of phenol (R) was 70.18% before optimized and 99.91% after optimized by response surface method (RSM) in phenol synthetic wastewater, and the removal rate of TOC was 72.81%. The operating conditions are: current density of 10 mA/cm2, initial phenol concentration of 100 mg/L, pH of 2, processing time of 270 min and electrolyte concentration (NaCl) of 0.7 mol/L. The R was 95.23% in actual coking water experiment with this process conditions, meanwhile the average removal rate of COD and NH3-N was 93.56% and 85.0%. The free radical quenching experiments result by different dose of tert-butanol (TBA) proved the dominant active material of·OH in oxidation process, the R was decreased from 99.91% to 73.24% (TBA: 0.7 mol/L) and 37.53% (TBA: 2.0 mol/L). The intermediates products most likely existed as hydroquinone, benzoquinone and catechol. synergistic effect on adsorption and oxidation of the electrode was certified. The whole process included three consecutive stages as adsorption, oxidation, desorption/oxidation. CEMs provided the active adsorption site and micro-electric field to improve the efficiency of oxidative degradation.

Electrochemical Cycloaddition Reactions of Alkene Radical Cations – a Route Towards Cyclopropanes and Cyclobutanes

New methods to promote single-electron transfer reactions play an increasingly important role in driving modern organic chemistry. Significant advances have been made in the field of photoredox catalysis1 and synthetic organic electrochemistry2 to expand the utility of radicals in organic synthesis.3 While the initial developments in synthetic organic electrochemistry date as far back as the early 19th century, only recently has it undergone an explosive revival and it is now an important part of synthetic organic chemistry.4 Undeniably, it provides a green alternative to known and new reactive intermediates by the promotion of organic reactions under mild conditions without the necessity for excessive amounts of hazardous and wasteful oxidants and reductants, metals4 or catalysts, making chemical synthesis highly atom economical.5 Our work describes mild and efficient electrochemical methods for [2+1] and [2+2] cycloaddition reactions of alkene radical cations. Anodic oxidation of olefins produces electrophilic alkene radical cations, which further react with nucleophilic diazo compounds in a formal [2+1] cycloaddition towards cyclopropane synthesis. This methodology is also applicable for [2+2] cycloadditions with styrene derivatives, validating this efficient electrochemical system for both cyclopropane and cyclobutane ring synthesis. The advantages of this methods include the mild, metal and catalyst free conditions, simple setup, and scalability of the procedure, as well as its potential use for industrial applications since the method requires non-expensive graphite electrodes.

Unravelling Ultrafast Li Ion Transport in Functionalized Metal-Organic Framework-Based Battery Electrolytes.

Nonaqueous fluidic transport and ion solvation properties under nanoscale confinement are poorly understood, especially in ion conduction for energy storage and conversion systems. Herein, metal-organic frameworks (MOFs) and aprotic electrolytes are studied as a robust platform for molecular-level insights into electrolyte behaviors in confined spaces. By employing computer simulations, along with spectroscopic and electrochemical measurements, we demonstrate several phenomena that deviate from the bulk, including modulated solvent molecular configurations, aggregated solvation structures, and tunable transport mechanisms from quasi-solid to quasi-liquid in functionalized MOFs. Technologically, taking advantage of confinement effects may prove useful for addressing stability concerns associated with volatile organic electrolytes while simultaneously endowing ultrafast transport of solvates, resulting in improved battery performance, even at extreme temperatures. The molecular-level insights presented here further our understanding of structure-property relationships of complex fluids at the nanoscale, information that can be exploited for the predictive design of more efficient electrochemical systems.

Perylene derivative and persulfate as highly efficient electrochemical system for constructing sensitive amperometric aptasensor

To design highly efficient electrochemistry system was important for construct simple and sensitive biosensors, which was crucial in clinical diagnosis and therapy. In this work, a novel electrochemistry probe N,N′-di (1-hydroxyethyl dimethylaminoethyl) perylene diimide (HDPDI) with positive charges was reported to show two-electron redox behavior in neutral phosphate buffer solution between 0 and -1.0 V. And K2S2O8 in solution could significantly increase the reduction current of HDPDI at −0.29 V, which was interpreted with cyclic catalysis mechanism of K2S2O8. Moreover, HDPDI as electrochemical probe and K2S2O8 as signal enhancer was used to design aptasensors for protein detection. Thrombin was used as target model protein. Thiolate ssDNA with thrombin-binding sequence was immobilized on gold electrode to selectively capture thrombin and adsorb HDPDI. The thiolate ssDNA without binding with thrombin was with random coil structure and could adsorb HDPDI through electrostatic attraction interaction. However, the thiolate ssDNA binding with thrombin became G-quadruplex structure and hardly adsorbed HDPDI. Thus, with increasing the concentration of thrombin, the current signal stepwisely decreased and was taken as detection signal. Compared with other aptasensors based on electrochemistry molecules without signal enhancer, the proposed aptasensors exhibited wider linear response for thrombin between 1 pg mL−1 and 100 ng mL−1 with lower detection limit 0.13 pg mL−1. In addition, the proposed aptasensor showed good feasibility in human serum samples.

A perspective on electrochemical conversion of CO2 to multicarbon chemicals in ionic liquids-based electrolytes

Carbon dioxide electroreduction (CRR) is a promising technology for both intermittent energy storage and emissions mitigation, but it faces challenges such as relatively high overpotential and poor selectivity. Introducing ionic liquids (ILs) into the CRR system has shown impressive activity for CO production, even in electrocatalysts that are primarily active for hydrogen evolution in aqueous electrolytes. However, converting CO2 to high-value C2+ chemicals in IL electrolytes suffers from limitations in *CO coverage, proton accessibility, and specific stabilization effects on *COOH. In this perspective, we emphasize the modification of the steady-state adsorption of *CO and other intermediates and the proton supply to enhance the CO2-to-C2+ conversion. More efforts need to be devoted to electrolyte modulation, involving the functional ILs design, the proton sources, and inorganic additive screening. It is also necessary to develop a descriptor for C2+ selectivity, explore the dynamic evolution of catalyst upon exposure to ILs, and construct novel catalyst/ILs hybrids. Furthermore, developing a molecular understanding of the electrode/ILs interface and the bulk phase of IL-containing electrolytes is essential for designing an efficient electrochemical system for C2+ generation.

Perylene Derivative and K2s2o8 as Highly Efficient Electrochemical System for Constructing Sensitive Amperometric Aptasensor

Perylene Derivative and K2s2o8 as Highly Efficient Electrochemical System for Constructing Sensitive Amperometric Aptasensor

Improvement of microbial extracellular electron transfer via outer membrane cytochromes expression of engineered bacteria

The effective contact between proteins on the electroactive membranes or nanowires determines the efficiency of the electroactive in bioelectrochemical systems (BES) biofilm. However, most electroactive biofilms are multi-layer bacterial aggregates, and the microorganisms in the outer layer cannot directly contact the electrode surface electron transfer. Herein, we construct a genetically engineered bacterium (GEB) that can express outer membrane cytochrome OmcA to improve the microbial extracellular electron transfer in the biofilm. The engineered bacterium improves the maximum power density of the mixed bacteria microbial fuel cell (MFC) by 2.36 times to 3.76 A cm−2, and increases the current density to 1.98 W m−2. This improved behavior was stable for at least three feeds. Adding the engineered bacteria generates a more compact biofilm structure and significantly improves the electrochemical performance of the anode biofilm. The engineered bacteria with the electron transfer function also increase the content of the OmcA gene in the bacterial community, thereby promoting the microbial extracellular electron transfer and increasing the proportion of electrogenic bacteria in the biofilm. With its expression of the conductive protein, the GEB can effectively improve the extracellular electron transfer efficiency of the outer layer bacteria in the biofilm of the MFC. Our study provides a new choice for building an efficient electrochemical system.

Mechanism and excellent performance of graphite felt as anodes in electrochemical system for Microcystis aeruginosa and microcystin-LR removal with no pH limitation nor chemical addition

• We reported a graphite felt (GF) -Pt electro-chemical system for effective algal removal for the first time. • M. aeruginosa cells and MC-LR were removed by 94% and 50%, respectively, after 30 min. • Chemicals are not needed. The GF-Pt system is available at a wide pH range (3–9). • The removal mechanism acts by direct discharging of anodes with superior electro-adsorption. • After 10 cyclic oxidation experiments, the algal cell removal efficiency was 83%. The outbreak of cyanobacterial blooms has posed a huge threat to drinking water safety and the natural water environment. Among the harmful cyanobacterial bloom types, Microcystis aeruginosa is a force to be recognized with. The purpose of this work was to develop an efficient and eco-friendly technology to curb harmful cyanobacteria blooms and purify bodies of water from polluting algal organic matter. A novel and efficient electrochemical system with a graphite felt (GF) anode and Pt cathode was proposed to treat water containing M. aeruginosa , and its performance and mechanism were investigated. Without chemical consumption, the GF-Pt system with a pH widely ranging from three to nine can inactivate approximately 90% of algal cells in a short time. The ideal GF-Pt system for the removal of algal cells and Microcystin-LR operated under a pH of 7 at 75 mA, achieving removal efficiencies of 94 ± 2% and 50%, respectively. The removal mechanism was determined to be the continuous direct discharging of the anodes, with superior electro-adsorption being the key to anodization efficiency enhancement. After only flushing and drying the GF anodes before reuse, the GF-Pt system was able to maintain an algal cell removal efficiency of 83% after 10 cycles.

Highly efficient removal of total nitrogen and dissolved organic compound in waste reverse osmosis concentrate mediated by chlorine radical on 3D Co3O4 nanowires anode

Reverse osmosis concentrate (ROC) from wastewater reclamation has posed significant disposal challenges due to its highly concentrated NH3-N, chloride ion and bio-refractory organics, and developing technologies for their removal are essential. Herein, we developed an efficient electrochemical system to remove total nitrogen and dissolved organic compound (DOC) simultaneously mediated by chlorine radical (Cl•), which is generated by activation of chloride ion existing in ROC on an inexpensive, three-dimensional Co3O4 nanowires. Results showed that the total nitrogen and total organic carbon removal were 98.2% and 56.9% in 60 min for synthetic ROC with 56 mg/L of NH3-N and 20 mg/L of DOC. The utilization of Co3O4 nanowires enhanced NH3-N degradation by 2.58 times compared with Co3O4 nanoplates, which were 1.69 and 17.5 times these of RuO2 and Pt. We found that structural Co3+/Co2+ acts as cyclic catalysis to produce Cl• via single-electron transfer, which convert NH3-N to N2 and lead to faster DOC degradation. This architecture provides abundant catalytic sites and sufficient accessibility of reactants. Small amount of nitrate generated by oxidation of NH3-N was further reduced to N2 on Pd-Cu/NF cathode. These findings provide new insights for utilization of waste Cl– and development of novel electrochemical system for ROC disposal.

Sustainable and continuous removal of trimethylamine in a bio‐photoelectrochemical reactor using g‐C3N4/TiO2 photocathode with power generation

AbstractBACKGROUNDTrimethylamine (TMA), as a harmful nitrogenous gas, is potentially toxic to animals and human beings. In recent years, the emission of TMA has caused huge environmental problems. TMA is strongly toxic and carcinogenic and requires efficient treatment technology. Photocatalysis and photoelectrocatalysis (PEC) have attracted great interest because of their environmental friendliness and high efficiency. The key problem is how to construct high‐efficiency systems and prepare high‐activity catalysts.RESULTSTo eradicate TMA in air, an efficient electrochemical system with bio‐anode and photocathode (g‐C3N4‐TiO2) was designed. It removed TMA in air continuously and efficiently, for both single‐cathode and double‐cathode systems. This is the first report about TMA removal in such integrated g‐C3N4/TiO2 photocathode and bio‐electrochemical system. Effects of reaction conditions were investigated, such as the TMA concentrations and flow rates. The highest efficiency for TMA removal was in an integrated PEC and microbial fuel cell (MFC) system with potassium persulfate (PS) activation. The double‐cathode PEC–MFC–PS system could remove more TMA (1.9 g m−3 h−1 versus 1.3 g m−3 h−1) compared with the double‐cathode PEC–MFC system.CONCLUSIONSA novel TMA treatment system – PEC–MFC system – was constructed, coupling PEC with MFC for continuous removal of TMA from air. Combined with activated PS, a PEC–MFC–PS system was designed and constructed and proved effective in oxidizing gaseous TMA and generating electricity at the same time, which has practical application prospects for the treatment of TMA pollution. © 2021 Society of Chemical Industry (SCI).

Study on the mechanism of tetracycline removal in electrocoagulation coupled with electro-fenton reaction system with Fe anode and carbon nanotube cathode

In this work, an efficient electrochemical system (Fe-CNT system) for the treatment of tetracycline (TC) was constructed using Fe plate anode and carbon nanotube (CNT) roller cathode. Compared with the traditional Fe-Fe electrocoagulation (EC) system, this Fe-CNT system exhibited higher TC removal rate and shorter reaction time. The best removal rate of 97.21% was achieved at pH of 7, the conductivity of 500 μS cm−1, initial TC concentration of 50 mg L-1, the voltage of 5 V, and reaction time of 25 min. The results demonstrated that the removal rate of total organic carbon was 52.79% at 25 min and 82.84% at 60 min, respectively. The excellent performance of the Fe-CNT system was mainly due to the use of CNT cathode slowed down the floatation in the system, which was conducive to the aggregation and growth of flocs. As a result, the flocs with larger size and more loose structure showed stronger adsorption and aggregation to organic molecules. At the same time, the concentration of hydrogen peroxide in-situ produced was in the range of 7.76 mg L-1 and 30.17 mg L-1. Furthermore, hydroxyl radical as the primary active specie was also produced on the cathode surface by electro-Fenton reaction, which could degrade TC rapidly. In addition, the intermediates involved in the degradation process of TC were identified, and the possible degradation paths were proposed. This work provides insights for improving the cathode utilization rate and removal ability of organic matter and adds a feasible option for the practical application of EC technology.

Fast-Charging Lithium-Sulfur Batteries Enabled via Lean Binder Content.

Next-generation energy storage devices such as lithium-sulfur batteries (LSBs) face several challenges including fast charging and high-power delivery. Thus, it is necessary to improve the stability of the electrodes with efficient electrochemical system. In this work, a durable sulfur cathode even at high rates is enabled via lean binder content. The binder consists of a chitosan cross-linked with a carboxylated nitrile-butadiene rubber (XNBR), which exhibits high affinity toward lithium polysulfide along with robust mechanical properties because of the synergistic effect of the polar chitosan and the elastomeric XNBR. Despite using extremely small content of binder (3wt%), the LSB shows a highly stable long-term cycling performance with capacity retention decay values of 0.026% and 0.029% after 500 cycles at 5 and 10 C. Moreover, the cell shows an outstanding specific capacity of 228 mAh g-1 at an ultrahigh charge-discharge rate of 20 C. This approach may significantly improve the design of the sulfur cathode and pave a facile way to fabricate commercially viable next-generation energy storage devices.

Electrochemical diselenylation of indolizines via intermolecular C-Se formation with 2-methylpyridines, α-bromoketones and diselenides.

An efficient electrochemical system for the construction of diselenytlated indolizines from available pyridines, ketones and diselenides under undivided electrolytic conditions was developed. No external oxidants and transition-metal catalysts are needed for achieving this three-component tandem reaction realizing C-C, C-N and C-Se bond formations.

Recent Progress in Graphene-Based Noble-Metal Nanocomposites for Electrocatalytic Applications.

The fast industrialization process has led to global challenges in the energy crisis and environmental pollution, which might be solved with clean and renewable energy. Highly efficient electrochemical systems for clean-energy collection require high-performance electrocatalysts, including Au, Pt, Pd, Ru, etc. Graphene, a single-layer 2D carbon nanosheet, possesses many intriguing properties, and has attracted tremendous research attention. Specifically, graphene and graphene derivatives have been utilized as templates for the synthesis of various noble-metal nanocomposites, showing excellent performance in electrocatalytic-energy-conversion applications, such as the hydrogen evolution reaction and CO2 reduction. Herein, the recent progress in graphene-based noble-metal nanocomposites is summarized, focusing on their synthetic methods and electrocatalytic applications. Furthermore, some personal insights on the challenges and possible future work in this research field are proposed.

Metal–Air Batteries: From Static to Flow System

AbstractAs an emerging battery technology, metal–air flow batteries inherit the advantageous features of the unique structural design of conventional redox flow batteries and the high energy density of metal–air batteries, thus showing great potential as efficient electrochemical systems for large‐scale electrical energy storage. This review summarizes the operating principles and recent progress of metal–air flow batteries from a materials and chemistry perspective, with particular emphasis on the latest advanced materials design and cell configuration engineering, which the authors divide into three categories based on the anode species: vanadium–air, zinc–air, and lithium–air flow batteries. Since some of the capabilities developed for metal–air static batteries can be leveraged for next‐generation flow systems, classical works on conventional metal–air batteries are selected and compared with the metal–air flow systems, highlighting the prominent advantages of the latter in achieving high energy capacity and long cycle performance. At the end, a general perspective on current challenges/opportunities and future research directions to promote the commercial application of the metal–air flow battery technology is provided. The aim is to provide a comprehensive overview and to set up a road map for guiding development from conventional static to advanced flow technologies of metal–air batteries.

High-Energy-Density Metal-Oxygen Batteries: Lithium-Oxygen Batteries vs Sodium-Oxygen Batteries.

The development of next-generation energy-storage devices with high power, high energy density, and safety is critical for the success of large-scale energy-storage systems (ESSs), such as electric vehicles. Rechargeable sodium-oxygen (Na-O2 ) batteries offer a new and promising opportunity for low-cost, high-energy-density, and relatively efficient electrochemical systems. Although the specific energy density of the Na-O2 battery is lower than that of the lithium-oxygen (Li-O2 ) battery, the abundance and low cost of sodium resources offer major advantages for its practical application in the near future. However, little has so far been reported regarding the cell chemistry, to explain the rate-limiting parameters and the corresponding low round-trip efficiency and cycle degradation. Consequently, an elucidation of the reaction mechanism is needed for both lithium-oxygen and sodium-oxygen cells. An in-depth understanding of the differences and similarities between Li-O2 and Na-O2 battery systems, in terms of thermodynamics and a structural viewpoint, will be meaningful to promote the development of advanced metal-oxygen batteries. State-of-the-art battery design principles for high-energy-density lithium-oxygen and sodium-oxygen batteries are thus reviewed in depth here. Major drawbacks, reaction mechanisms, and recent strategies to improve performance are also summarized.

Core-shell hyperbranched chitosan nanostructure as a novel electrode modifier

The present study reports, for the first time, the development and use of core-shell amino-terminated chitosan (Cs) hyperbranched nanoparticles (HBCs-NH2 NPs) as a novel natural polymer-based electrode modifier for efficient electrochemical systems. The electrochemical activity of the developed HBCs-NH2 NPs as compared to Cs NPs was identified by standard oxidation-reduction reactions of ferricyanide. The oxidation-reduction peaks height was about twofold higher than the response of Cs-modified electrode. On the other hand, NADH oxidation at the nanostructured surfaces confirmed the electrocatalytic activity where the oxidation of NADH appeared at a lower overpotential (from 805mV to 635mV vs Ag/AgCl). Eventually, a diffusion-controlled process was confirmed from the scan rate effect.

Electro-Fenton method for the removal of methyl red in an efficient electrochemical system

To promote treatment efficiency, an efficient undivided electrochemical system using a graphite-polytetrafluoroethylene (PTFE) cathode with high production rate of hydrogen peroxide and current efficiency under wider pH ranges was applied to the electro-Fenton oxidation of a model azo dye, methyl red. The influences of operating parameters including electrolyte Na 2SO 4 concentration, cathodic potential, pH, Fe 2+ concentration and initial methyl red concentration were investigated. At the conditions of cathodic potential of −0.55 V versus SCE, pH 3, Fe 2+ concentration of 0.2 M, methyl red of initial concentration of 100 mg/L could be removed 80% in 20 min. Due to the consumption of ferrous ion and formation of hard-to-treat intermediates during treatment, the removal of methyl red was found degraded at two different stages, and the second stage was much slower than the first one.