Table of contents

Tin was electrodeposited for the first time on copper electrode with different pulse current densities and cycle times. The optimized one (namely CuSn_(30–12C)) has a rougher surface, a smaller electron transport resistance, and a larger electrochemical surface area than others, exhibiting the best catalytic activity, a faster Faraday process, and the highest selectivity for the production of HCOO⁻ in ERCO₂. At −1.6 V vs SCE, a HCOO⁻ Faraday efficiency of 84.5% was achieved and the current density was 45.4 mA cm⁻² at −2.0 V vs SCE. In addition, this optimized electrode also has a catalytic stability of up to 23 h.

Using 1,2-Acenaphthenedione as an example, cyclic voltammetry, chronoamperometry, coulometry, electrolysis and digital simulation were used to show that electroreduction of carbonyl compounds in the presence of nitromethane in 0.1 M Bu₄NClO₄/DMF proceeds via the ECE mechanism gives rise nitromethane anion initiating cyclic nitroaldol (Henry) process leading to β-nitroalcohols.

Electrochemical oxidation of methane in the absence of chemical oxidants offers the potential to directly synthesize high value hydrocarbons at low temperatures. Experimental results demonstrate methane oxidization at oxidized Pt electrodes in liquid superacid electrolytes. Ethane and ethylene are observed as products under chronoamperometric experiments at room temperature. Faradaic efficiencies for C₂ products range from 5% to 25% at anodic potentials between 0.8 to 1.4 V vs RHE. A generalized Lewis-acid Pt²⁺ mechanism including methylidene coupling is proposed.

Reasonable design of electrocatalyst based on abundant earth elements is of great importance for sustainable energy use. Transition metal nitrogen doped carbon (TM-N/C) materials demonstrate excellent catalytic activity. However, there is still a lack of comprehensive understanding of these TM-N/C-systems. Herein, we have developed an effective approach to develop highly active and stable Cu promoted N-doped carbon (Cu-N/C) catalysts. The impacts of copper doping and temperature of pyrolysis on catalytic performance have been studied. The Cu-NC-800 catalysts exhibited excellent catalytic activity and stability with an onset potential (E_o) of 0.99 V and half-wave potential (E_1/2) of 0.85 V. It also shows strong the long-term stability. The synergistic effect between Cu (II)-N ligand and Cu⁰ nanoparticles is high, the active center is small, the transfer of mass is rapid, and the electrocatalytic efficiency is increased. The findings showed that the non-noble metal-based catalyst's bifunctional oxygen electrode activities prepared in this study were as high as those of commercial oxygen-based, noble metal catalysts.

Caucasian whortleberry (Vaccinium Arctostaphylos L.) is rich in anthocyanins, which possesses a wide range of biological and pharmaceutical activities. Electrochemical behavior of V. Arctostaphylos extract of dried fruit was performed by cyclic voltammetry and differential pulse voltammetry in aqueous solution. The results show that the level of delphinidin 3-O-glucoside (D3-OG) compound is higher than petunidin 3-O-glucoside (P3-OG) and malvidin 3-O-glucoside (M3-OG) level. This extract has a high solubility in water, and the potential-pH diagram indicates that the D3-OG capable oxidized to D3-OG_OX with two electron/two proton process. D3-OG compound has a high antioxidant power because of the oxidation peak potential is low. Furthermore, total antioxidant capacity (1.475 C g⁻¹) was determined by charges under of first oxidation peak. The antioxidant activity of three anthocyanins against Xanthine oxidase, Myeloperoxidase, NADPH oxidase, cytochrome P450 3A4 and 2B4 (ROS generation enzymes) has been performed through molecular docking studies. The results indicated that all the anthocyanins (D3-OG, P3-OG and M3-OG) bound exclusively to the binding site of ROS generation enzymes and have a remarkable role in suppressing the destructive effects of oxidative stress in the biological system of the human body. Also, D3-OG as a major anthocyanin of Vaccinium Arctostaphylos L. extract has an inhibition effect against the COVID-19 outbreak. Electrochemical approaches provided a simple, fast, low cost, green, and high sensitivity methods for investigation of electroactive compounds in plant extracts.

Electric power can be generated from renewable energy sources such as solar and wind, making electrocatalytic hydrogenation an important technology to reduce carbon dioxide emissions in the organic synthesis industry. In the present work, the electrocatalytic semihydrogenation of diphenylacetylene was carried out in a proton exchange membrane (PEM) reactor with carbon-supported Pt, Pd, and Pt–Pd alloy cathode catalysts. Diphenylacetylene introduced into the PEM reactor at less negative potentials underwent electrocatalytic hydrogenation to provide cis-stilbene as a main stereoisomer, with excellent current efficiencies. Among the investigated catalysts, the Pt–Pd alloy with a composition of 1(Pt):99(Pd) was found to be the most suitable for achieving both high cis-stilbene selectivity and a high production rate (partial current density) for cis-stilbene.

The electrochemical reduction mechanisms of diprotonated tetraphenylporphyrin (H₂TPP) and mono- and diprotonated octaethylporphyrin (H₂OEP) were studied in tetrabutylammonium perchlorate/benzonitrile. The diprotonated forms of both porphyrins undergo two one-electron reversible reduction processes forming isophlorin. Contrastingly, monoprotonated H₂OEP is reduced in a single process involving a two-electron one-proton transfer that yields two types of short-lived intermediates, isophlorin and neutral phlorin. The existence of intermolecular proton transfer reactions, from the parent protonated porphyrin to the isophlorin or neutral phlorin, to form phlorin cation species (isophlorin protonated at the meso-position) was demonstrated. In-situ UV–vis spectroelectrochemical experiments allowed us to identify the absorption of the isophlorin species of H₂TPP but not of H₂OEP. These results show that the lack of phenyl substituents increases the rate of protonation at the meso-position. Finally, it was demonstrated that the protonation of the porphyrin macrocycle not only lowers the reduction potentials but also increases the reactivity of the electrogenerated species.

Corrosion inhibition of mild steel in hydrochloride acid solution was performed by a two pyrazole carboxamides named 5-(4-(dimethylamino)phenyl)-3-phenyl-4,5-dihydro-1H-pyrazole-1-carboxamide DPC-1 and (E)-5-(4-(dimethylamino)phenyl)-3-(4-(dimethylamino)styryl)-4,5-dihydro-1H-pyrazole-1-carboxamide DPC-2 using weight loss measurements, Tafel polarization curves and electrochemical impedance spectroscopies (EIS). The obtained results show that DPC-1 and DPC-2 are effective corrosion inhibitors in 1 mol l⁻¹ HCl solution. The inhibition efficiency η (%) increases with the increase of inhibitors concentration to reach 84.56% at 4 × 10⁻⁴ mol l⁻¹ and 80% at 1.6 × 10⁻⁴ mol l⁻¹ for DPC-1 and DPC-2 at 303 K, respectively. The adsorption of synthesized pyrazoles on MS surface obeys the Langmuir adsorption isotherm. Tafel polarization curves reveal that DPC-1 and DPC-2 acts as a mixed-type inhibitor and EIS spectra show the increase of the transfer resistance with the inhibitors concentration. The SEM surface analysis shows the formation of protective organic film on steel surface. The relationship between the inhibition performance of pyrazoles and their structural parameters was investigated using DFT calculations.

Because of the necessity of carry out electrolysis reactions with considerable quantity of organic molecules, the balance between solubility of starting material, solution conductivity and electrochemical stability of medium and intermediates are key factors in organic electrosynthesis. HFIP has several properties that favor its use in this research area as solvent, among them, its high hydrogen-bond donor has opened the possibility of fine tuning reactivity, mainly in anodic reactions because of the helpful effect on the stability of positive intermediates. The cost of this solvent has limited its broad application in chemistry, including electrosynthesis, but the possibility of using mixtures with other cosolvents has demonstrated to help to expand its use without losing the beneficial effect on the intermediates. In recent years several HFIP mixtures (HFIP/MeOH, HFIP/CH₂Cl₂, HFIP/H₂O, HFIP/ACN, HFIP/MeNO₂) have permitted the control the chemical microstructure of the electrolysis media and have let to adjust the solvent properties to fulfill the necessity of electrosynthesis. In this review will be discussed the general properties of HFIP and the mixtures reported to carry out electrochemical synthetic transformations of organic molecules, as well as the reactions where has been demonstrated the beneficial effect of HFIP solvent mixtures in the control of the electrogenerated intermediates. This approach has succeeded in organic electrosynthesis.

There has been a considerable increment in the atmospheric CO₂ concentration, which has majorly contributed to the problem of global warming. This issue can be extenuated by effectively developing microbial electrosynthesis (MES) for the sequestration of CO₂ with the concurrent production of biochemical and biofuels. Though the MES technology is in its infancy, it has exhibited enormous potential for sustainable mitigation of CO₂ and bioelectrosynthesis of multi-carbon organic compounds. The problem of storage of excess renewable electrical energy by conventional means can also be alleviated by employing MES, which stores it in the form of C–C bonds of chemicals. This review focuses on the various aspects of MES and recent developments made in this field to overcome its bottlenecks, such as the lower yield of organic compounds, separation of products of higher chain organic compounds, etc. In particular, the microbial catalysts and cathode materials employed in MES have also been emphasized. Keeping in mind the potential of this innovative technology, researchers should focus on improving the yield of MES by developing novel low-cost cathode materials and discovering efficient and robust micro-organisms, which would be a significant step forward towards the further advancement of this technology.

Electrochemical analyses of phenylthiocyclopropane derivatives and bis(arylthio)cyclopropanes were comparatively studied by cyclic voltammetric measurements. Based on the substituent effects on their oxidation potentials, a cyclopropane ring was confirmed to have a double bond system as reported. Anodic fluorination of phenylthiocyclopropanes resulted in the formation of sulfoxide and/or ring opening fluorinated products while 1,1-bis(arylthio)cyclopropanes afforded mainly desulfurizative monofluorinated cyclopropanes and sulfoxides together with ring opening fluorinated products. This is the first successful electrochemical fluorination of a cyclopropane ring.

Synthesis of zirconium oxide (zirconia) (ZrO₂) nanoparticles (ZNPs) through gel combustion technique as well as their structural and morphological characterization using XRD, SEM and TEM forms the central theme of this work. Along with structural and morphological characterization, an electrochemical detection of Serotonin (5-HT) is described using ZNPs Modified Carbon Paste Electrode (ZMCPE). The XRD results confirms that particles are well crystallized in tetragonal phase with average particle size of 35 nm. From SEM it can be observed that, the materials formed is porous in nature and the particles are seems to be uniform in size. HRTEM reveals that, the particles size in the order of 30–40 nm and the crystallinity was supported by SAED pattern of the ZNPs and these results are in close agreement with the results obtained through XRD. The Electrochemical detection of Serotonin (5-HT) was performed through cyclic voltammetric and differential pulse voltammetric method at different circumstances like concentration of the analyte, applied potentials and pH of the medium. The DPV experiments shows that ZMCPE displays high sensitivity for the quantification of serotonin (5-HT) in the range 10–50 μM and the limit of detection is 0.585 μM. The ZMCPE gives good reproducibility, high catalytic activity and sensitivity for the electrochemical quantification of Serotonin.

A facile electrochemical oxidation of pyridyl carbinol based on Manganese dioxide-Phosphate (MnO₂-Pi) was fabricated by electro-deposition of MnO₂-Pi on Porous carbon nanospheres (PCN) modified carbon fiber paper (CFP) electrode. A simple working electrode was developed initially by coating Monkey Pod (MP) derived PCN on carbon fiber paper (CFP) electrode. Voltammetric deposition of MnO₂-Pi on PCN/CFP electrode was carried out in an electrolyte containing phosphate buffer and KMnO₄. The modified electrodes (PCN/CFP and MnO₂-Pi-PCN/CFP) were characterized by different physicochemical methods and electroanalytical techniques like cyclic voltammetry and AC impedance spectroscopy. Inorganic phosphate (Pi) and MnO₂ centers present on PCN/CFP electrode plays a major role towards oxidation of pyridyl carbinol electrochemically. The proposed MnO₂-Pi-PCN/CFP electrode was effectively applied for the electrochemical oxidation of pyridyl carbinol in TEMPO medium.

The contamination with water of the cathodic ACN-Et₄NBF₄ solution gave us the opportunity to investigate alkyl isocyanate reactivity toward electrogenerated anions. The cathodic reduction of a ACN-Et₄NBF₄ solution led to the formation of both hydroxide and cyanomethyl anions. The reaction of the catholyte with cyclohexylisocyanate led to the exclusive formation of acetamidated product, with no traces of cyanomethylated one. On the contrary, when reacting with benzaldehyde only the cyanomethylated was isolated. Considering that the acetamidated product of benzaldehyde is reported to be unstable (thus its formation cannot be excluded), various experiments were carried out in order to understand the anomalous reactivity of cyclohexylisocyanate. Moreover, computational analysis allowed to state the higher stability of acetamidated product with respect to the cyanomethylated one. The possibility of a concerted reaction, instead of acetamide anion formation prior to the reaction, is still an open question.

Functional properties of flexible reflective electrochromic composites comprised of polyaniline-coated metallized textile were investigated in this study. Polyaniline was deposited electrochemically onto metal-plated textile fabric and the resulting composites were investigated by electrochemical means as well as by optical-digital colour analysis. Surface morphology and microstructure were evaluated using scanning electron microscopy. Electrochromic performance of the conducting textile and polyaniline composites was optimized by tuning the applied electrochemical switching parameters. Electrochromic textile composites exhibited reversible colour change with good visual contrast between the coloured and bleached states. Functional stability of electrochromic metal-plated textile/polyaniline composite was evaluated by continuous switching between the colored states for 100 cycles. Herein presented concepts might find future use in the development of flexible, colour changing visual interfaces and/or wearable technology, the Internet of things (IoT) devices and optical sensors.

The electrochemical oxidation of 4-methylcatechol (1a), 4-tert-butylcatechol (1b), and 3-methylcatechol (5) has been studied in the presence of 1,3-cyclopentadiene (3) in an ethanol/water (60:40 v/v) mixture using cyclic voltammetry, controlled-potential coulometry, and preparative electrolysis. The electrochemically generated benzoquinones took part, as dienophiles, in a Diels-Alder reaction with 3 to form methanotetrahydronaphtoquinones through an EC mechanism. The cycloaddition of 3-methyl-o-benzoquinone (5a) to 3 is highly regioselective, affording product 6, a novel regioisomer. It is proposed that the cycloaddition would occur with the benzoquinones adsorbed on the carbon electrode surface. The controlled potential electrolyses were carried out in a one-compartment cell.

Cyclic voltammetry and controlled-potential (bulk) electrolysis have been employed to investigate the direct electrochemical reduction of acetochlor (1) at carbon and silver cathodes in dimethylformamide. Voltammograms of 1 exhibit a single irreversible cathodic peak at both cathode materials. Catalytic properties of silver towards carbon–halogen bond cleavage are evidenced by a positive shift in the reduction of acetochlor as compared to the more inert glassy carbon electrode. Voltammograms in the presence of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), and comparisons of calculated relative interaction energies between acetochlor, possible intermediates, and deschloroacetochlor in the presence of different proton donors, suggest strong hydrogen-bonding interactions between HFIP and a carbanion intermediate. Addition of HFIP to electrolysis conditions promotes complete reduction at both cathode materials, with formation of deschloroacetochlor in high yields. In deuterium labelling studies, the use of DMF-d₇ led to no evidence for deuterium atom incorporation. However, when HFIP-OD or D₂O were employed as a proton source, substantial amounts of deuterated deschloroacetochlor were observed. A mechanism for the reduction of acetochlor is proposed, in which radical intermediates do not play a significant role in reduction, rather a carbanion intermediate pathway is followed.

Cascade processes, including electron transfer (E), chemical reaction (C), and backward electron transfer (E), are known as EC-backward-E mechanisms; however, they are rarely observed directly. Herein, we demonstrate that direct observation of EC-backward-E processes in radical cation Diels-Alder reactions is possible using cyclic voltammetry measurements. Formal expressions for the plausible reaction mechanisms provide a reasonable understanding of the processes, which are also supported by the highest occupied molecular orbitals and spin density distributions plotted from density functional theory calculations.

Graphene oxide (GO), a derivative of graphene, has attracted widespread attention due to its easy functionalization and excellent water solubility. Therefore, a method for efficiently producing GO shoule be developed. Although the traditional chemical oxidation method is broadly employed for GO synthesis, it entails problems, such as long time-consuming, explosive danger and easy to pollute the environmental. Recent research on using electrochemical methods for GO synthesis has achieved a breakthrough, that is, the realization of pollution-free, safe and efficient large-scale preparation of high-quality GO within a few hours. This article introduces the principle of electrochemical GO synthesis and summarizes the progress of research on GO preparation via two-electrode, three-electrode and electrolyte exfoliation with focalize on product quality and quantity. The challenges in high-quality electrochemical GO production and future research directions are also presented.

Radical cation initiated cyclization reactions can be triggered by the one electron oxidation of an electron-rich olefin using either electrochemistry or visible light and a photoredox catalyst. In principle, the two methods can be used to give complimentary products with the electrolysis leading to products derived from a net two electron oxidation and the photoelectron transfer method being compatible with the formation of products from a redox neutral process. However, we are finding an increasing number of oxidative cyclization reactions that require the rapid removal of a second electron in order to form high yields of the desired product. In those cases, the electrochemical method can provide a superior approach to accessing the necessary two electron oxidation pathway. With that said, it is a combination of the two methods that provides the mechanistic insight needed to understand when a reaction has this requirement, and we are finding that the use of photoredox catalysis in combination with electrochemical methods is changing our understanding of even the most successful anodic cyclization reactions run to date.

We present a sacrificial anode-free approach to reductive homocoupling of organohalides that does not require a co-catalyst. In this approach, a divided electrochemical cell with aprotic and aqueous compartments separated by an anion exchange membrane enables coupling of the cathodic homocoupling reaction with anodic oxidation of urea. We show that, in contrast with traditional one-compartment cells relying on sacrificial anodes, the proposed cell configuration maintains stable cell voltage in the course of galvanostatic electrolysis. A synthetic potential of this method was assessed using a series of 13 organic bromides that demonstrated a strong dependence of the reaction outcome on the structure of the organic substrate, more specifically, the dissociation energy of the C–Br bond and the redox properties of formed radicals, which are discussed in detail. While not being suitable for the synthesis of byarylstructures, this method is excellent for C(sp³)-C(sp³) coupling to corresponding dimeric products with up to quantitative yields. Simultaneous electrochemical treatment of nitrogenous waste in the adjacent half-cell provides an additional incentive for wide adaptation of this sustainable synthetic approach.

The interaction of L-cysteine with bismuth compounds bismuth(III) salicylate, bismuth(III) citrate, and bismuth(III) nitrate, was studied at pH 1.0 (0.100 M HNO₃ and 0.100 M HCl) and pH 7.4 MOPS buffer by cyclic voltammetry at glassy carbon and boron-doped diamond electrodes. pH 1.0, at which bismuth (III) exists as the simple Bi³⁺ ion, was chosen to approximate the acid strength of stomach contents. pH 7.4, at which bismuth(III) exists as BiO, was used for its similarity to general physiological conditions. The amino acid L-cysteine was chosen because its sulfhydryl group undergoes intense interaction with many metal cations, serving as a model for cysteine-containing proteins in the digestive system. It was determined that Bi(III) and L-cysteine (Cys) form soluble complexes at both pH 1.0 and pH 7.4. UV–vis spectroscopic investigations support interaction of Bi(III) and L-cysteine to form a 1:2 Bi(III): Cys complex in pH 7.4 MOPS buffer. L-cysteine addition to solutions of the pharmaceutical bismuth(III) salicylate was found to alter the voltammetric behavior of the salicylate complex. These results, especially at pH 1.0, are relevant to understanding the interaction of various cysteine-containing proteins in the human digestive system with bismuth pharmaceuticals and may help guide future explorations of bismuth formulations.

Glucose is a desirable source of energy for fuel cell applications. However, its slow oxidation rate on nonprecious metal electrodes has been a challenge. Viologens can potentially mitigate this challenge as they homogeneously oxidize glucose and then transfer electrons to inert electrodes with fast kinetics. This study aims to better understand the factors that determine the effectiveness of viologen as a mediator for glucose oxidation. The relative significance of the key physical processes including homogeneous reaction, mass transfer, and electrochemical reaction was evaluated by dimensional analysis and detailed simulations. While all processes were important under certain conditions, mass transfer was the principal limiting step. Mass transfer was initially improved by flow; however, this impact was counterbalanced by the decreased concentration of the reduced mediator at high flow rates. The maximum obtainable current density was close to 200 mA cm⁻², which corresponded to a predicted anode polarization of 300 mV. This current density is noticeably higher than rates available from biological cells and comparable to values for precious-metal-based cells. Thus, viologen-mediated fuel cells offer high rates without the additional cost associated with precious metal electrodes. Finally, the approach presented can be used for process development and optimization of any mediated system.

Land application of manure can be a sustainable supply chain practice that improves soil quality by recycling important nutrients contained in animal waste. Yet, runoff of phosphorus and nitrogen nutrients contained in the animal waste has contributed to significant watershed eutrophication. Recovery of the dissolved nutrient species as a condensed solid fertilizer product would increase sustainability of the agricultural supply chain, while reducing watershed pollution. This study was conducted to evaluate the recovery of phosphorus (primarily) as struvite using an electrochemical process while varying temperature, applied cathodic potential, turbulence and Ca²⁺ concentration. High phosphorus recovery with high current efficiency and low specific energy consumption was possible at 20 °C, −1.1 V vs Ag/AgCl at the cathode, and a Reynolds number of 9150 in the absence of Ca²⁺ when the Mg:N:P ratio was 1.37:1:1. Further, a thermodynamic model of the waste solution indicated an increase in Ca²⁺ concentration, which impedes struvite recovery, can be negated by increasing dissolved Mg²⁺ concentration and operating at a pH below NH₃ volatilization.

A critical review of classical and improved electrodes, electrocatalysts and reactors is provided. The principles governing the selection of electrochemical flow reactor or progression of a particular design for laboratory or pilot scale are reviewed integrating the principles of electrochemistry and electrochemical engineering with practical aspects. The required performance, ease of assembly, maintenance schedule and scale-up plans must be incorporated. Reactor designs can be enhanced by decorating their surfaces with nanostructured electrocatalysts. The simple parallel plate geometry design, often in modular, filter-press format, occupies a prominent position, both in the laboratory and in industry and may incorporates porous, 3D or structured electrode surfaces and bipolar electrical connections considering the reaction environment, especially potential- and current-distributions, uniformity of flow, mass transport rates, electrode activity, side reactions and current leakage. Specialised electrode geometries include capillary gap and thin film cells, rotating cylinder electrodes, 3-D porous electrodes, fluidised bed electrodes and bipolar trickle tower reactors. Applications span inorganic, organic electrosynthesis and environmental remediation. Recent developments in cell design: 3D printing, nanostructured, templating 3D porous electrodes, microchannel flow, combinatorial electrocatalyst studies, bioelectrodes and computational modelling. Figures of merit describing electrochemical reactor performance and their use are illustrated. Future research and development needs are suggested.

Electrolyte ions have a profound impact on the reaction environment of electrochemical systems and can be key drivers in determining the reaction rate and selectivity of electro-organic reactions. We combine experimental and computational approaches to understand the individual effect of the size and concentration of supporting alkali cations, as well as their synergies with other electrolyte ions on the electrosynthesis of adiponitrile (ADN). The size of supporting alkali cations influences the surface charge density, availability of water molecules, and stability of reaction intermediates. Larger alkali cations can help limit hydrogen evolution and the early protonation of intermediates by lowering the availability of water molecules in the near electrode region. A selectivity of 93% towards ADN was achieved at −20 mA cm⁻² in electrolytes containing cesium phosphate salts, ethylenediaminetetraacetic acid, and tetraalkylammonium ions (TAA ions). Electrolytes containing only supporting phosphate salts promote the early hydrogenation of intermediate species leading to low ADN selectivities (i.e., <10%). However, the combined effect of alkali cations and selectivity-directing ions (i.e., TAA ions) is essential in the enhancement of ADN synthesis. The insights gained in this study provide guidelines for the design of aqueous electrolytes that improve selectivity and limit hydrogen evolution in organic electrosynthesis.

Metal-organic frameworks, a class of highly crystalline porous materials, have gained intense research interest in material science in the last decade due to its intriguing chemistry and unique properties which lead to diverse applications. There are different methods for the development of MOF thin film in lab scale and its fabrication in electronic devices. However, the harsh reaction conditions, prolonged synthesis time, complex experimental setup etc. limit its application. Here, the electrochemical synthesis offers the advantages of mild reaction conditions, real time tuning of applied potential, short reaction time etc. which make the selective deposition of MOF on various conducting substrates facile. In this review, we focus on the direct electrochemical synthesis of MOF with emphasis on anodic and cathodic electrodeposition. The two different synthetic methods are explained in detail with a detailed review on its progress since its development. The electrosynthesis of MOF is still in its infancy stage and therefore the challenges and future perspectives associated with it are also discussed.

In this work, a carboxylic acid-functionalized graphene (Gr-COOH)-modified glassy carbon electrode (GCE) (Gr-COOH/GCE) was developed and applied for the sensitive determination of hydroquinone in pharmaceutical products. Gr-COOH on a GCE was used as an adsorbent in adsorptive anodic stripping voltammetry (AdASV). Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV) and AdASV were employed to characterize the surface morphology and electrochemical behavior of the Gr-COOH/GCE. The sensitivity of the Gr-COOH/GCE was 3, 7, and 10 times higher than those of a Gr/GCE, GCE-COOH and bare GCE, respectively. Several operational parameters, including the amount of Gr-COOH, preconcentration potential and preconcentration time, were optimized. Under optimum conditions, the peak current response linearly increased with the hydroquinone concentration in the range of 0.1–40.0 μmol l⁻¹ (r = 0.999) with a high sensitivity of 19.86 μA (μmol l⁻¹)⁻¹ cm⁻² and a limit of detection of 0.04 μmol l⁻¹. This proposed modified electrode exhibited good repeatability, accuracy and precision. It also showed good anti-interference properties. This method was successfully applied to detect hydroquinone in skin-lightening products.

In addition to electrochemical and photochemical approaches, the photoelectrochemical method using semiconductors as photoelectrodes is a third type of approach in the field of synthetic organic chemistry that enables precise control of single electron transfer (SET) reactions. Herein, we report mechanistic studies on TiO₂ photoelectrochemical redox neutral reactions, where both reductive and oxidative SET are involved, using radical cation [2 + 2] cycloadditions as models. In the presence of platinum nanoparticles or molecular oxygen as electron sink or electron acceptor, respectively, the mechanistic details for the photoelectrochemical reactions can be investigated because the excited electron at the conduction band of TiO₂ is removed.

Herein, we report the synthesis of titania supported Rh(0) nanoparticles (Rh⁰/TiO₂) as electrocatalyst for hydrogen evolution reaction (HER) in acidic medium. Rhodium nanoparticles with an average particle size of 2.54 nm are found to be well-dispersed on TiO₂ surface. Rh⁰/TiO₂ with very low loading density (3.79 μg cm⁻²) was attached on the glassy carbon electrode (GCE) by drop-casting method. Electrocatalytic performance of modified GCE was investigated via linear sweep voltammetry (LSV) in 0.5 M aqueous H₂SO₄ solution after 2000 cycle treatment (Rh⁰/TiO₂-2000) and it was found that Rh⁰/TiO₂-2000 on GCE exhibits superior electrocatalytic activity (TOF: 11.45 s⁻¹ at η = 100 mV, η₀:−28 mV, η_{10 mA cm}⁻²: −37 mV, j₀: 0.686 mA cm⁻² and Tafel slope: 32 Mv dec⁻¹). More importantly, it provides outstanding long-term stability (10000 cycles) at room temperature for HER, which makes Rh⁰/TiO₂-2000 a promising electrocatalyst for hydrogen generation.