Electrochemical Reduction

A new mechanism of O 2 reduction, which follows different principles than those generally accepted for describing ORR reduction on heteroatom-doped carbons, is suggested. It is based on the ability of oxygen to strongly adsorb in narrow hydrophobic pores. In this respect, a cellular vitreous carbon foamgraphene oxide composite was synthesized. The materials were doped with sulfur and nitrogen and/or heat-treated at 950 o C in order to modify their surface chemistry. The resultant samples presented a macro/microporous nature and were tested as ORR catalysts. To understand the reduction process, their surface was extensively characterized from the texture and chemistry points of view. The treatment applied markedly changed the volumes of small micropores and the surface hydrophilicity/polarity character. The results showed that the electron transfer number was between 3.87-3.96 and onset potential reached 0.879 V for the best performing sample. It is noteworthy that the best performing sample has the highest volume of pores smaller than 0.7 nm while no heteroatom doping. The hydrophobicity and the strong adsorption forces provided by these pores to pull oxygen inside are the possible reasons for the observed excellent performance. A decrease in the volume of these pores resulted in a decrease in the catalytic performance. When the surface was modified with heteroatoms, the performances further worsened because of the induced hydrophilicity.

The recently proposed highly efficient route of pyridine‐catalyzed CO2 reduction to methanol was explored on platinum electrodes at high CO2 pressure. At 55 bar (5.5 MPa) of CO2, the bulk electrolysis in both potentiostatic and galvanostatic regimes resulted in methanol production with Faradaic yields of up to 10 % for the first 5–10 C cm−2 of charge passed. For longer electrolysis, the methanol concentration failed to increase proportionally and was limited to sub‐ppm levels irrespective of biasing conditions and pyridine concentration. This limitation cannot be removed by electrode reactivation and/or pre‐electrolysis and appears to be an inherent feature of the reduction process. In agreement with bulk electrolysis findings, the CV analysis supported by simulation indicated that hydrogen evolution is still the dominant electrode reaction in pyridine‐containing electrolyte solution, even with an excess CO2 concentration in the solution. No prominent contribution from either a dire...

Silicon (Si) films were deposited on low-cost graphite substrates by the electrochemical reduction of silicon dioxide nanoparticles (nano-SiO2) in calcium chloride (CaCl2), melted at 855 °C. Cyclic voltammetry (CV) was used to analyze the electrochemical reduction mechanism of SiO2 to form Si deposits on the graphite substrate. X-ray diffraction (XRD) along with Raman and photoluminescence (PL) results show that the crystallinity of the electrodeposited Si-films was improved with an increase of the applied reduction potential during the electrochemical process. Scanning electron microscopy (SEM) reveals that the size, shape, and morphology of the Si-layers can be controlled from Si nanowires to the microcrystalline Si particles by controlling the reduction potentials. In addition, the morphology of the obtained Si-layers seems to be correlated with both the substrate materials and particle size of the feed materials. Thus, the difference in the electron transfer rate at substrate/na...

The faradaic efficiency of CO 2 electroreduction is significantly affected by the thickness of Pd nanoshells on Au cores. The ratio of hydrogen evolution to CO 2 reduction was determined by differential electrochemical mass spectrometry. Decreasing the Pd shell thickness from 10 to 1 nm leads to a twofold increase in faradaic efficiency.

We investigated the electrochemical reduction behavior of folic acid (FA) at multi-walled carbon nanotube-polyvinylsulfonate (MWCNT-PVS) composite film modified glassy carbon electrode (GCE) using cyclic voltammetry (CV). FA undergoes a 2e -/2H + transfer electrochemical reduction process at -0.7 V with respect to Ag/AgCl reference electrode in pH 7. The reduction peak current increased linearly with the increase in concentration of FA. So far no reports are available for the amperometric determination of FA utilizing the reduction process occurring at negative over potential (-0.7 V). We attempted the amperometric studies making use of this reduction process at -0.7 V. MWCNT-PVS modified electrode showed good amperometric response in the wide linear range from 5.3 x 10 -5 M to 1.7 x 10 -3 M with a sensitivity of 0.1737 μA μmol -1 cm -2 . The surface morphology of MWCNT-PVS film was done by scanning electron microscopy (SEM) and the interfacial electron transfer phenomenon at the modified electrode surface was studied using electrochemical impedance spectroscopy (EIS). The studies showed that MWCNT is well dispersed in PVS and the composite film possesses less electron transfer resistance making it a promising material for electrocatalytic and biosensing applications.

We report here on the electrochemical reduction of S-nitrosothiol species (RSNO). Nitric oxide (NO) is the reported common product from electrochemically reduced RSNOs at physiological pH. However, studies here at pH 7.4 show that during the reduction of RSNOs (-0.6 V to -0.9 V, vs. Ag/AgCl), no significant amount of NO is detected. Gas analysis suggests RSNO are reduced to nitrous oxide (N 2 O) at pH 7.4 and can only be converted back to NO at more oxidizing voltages. Interestingly, at pH 4.0, a direct one-electron reduction of RSNOs appears to occur and generates significant amounts of NO from RSNO species.

The electrochemical reduction of the disperse azo dyes Red1, Red13 and Orange1 (Or1) was investigated in the RTILs [C 4 mim][NTf 2 ] and [C 4 mpyrr][NTf 2 ], and in contrast with their behavior in conventional aprotic solvents, was shown to proceed via a reversible one electron step to form stable radical anion, which is further reduced at more negative potentials to the dianion. In [C 4 mpyrr][NTf 2 ], cleavage of the N-H bond on the secondary amine was inferred for Orange1, and the ease at which this cleavage occurred is rationalized in terms of acidity of the amine moiety. The ease of reduction was observed to decrease in the order Or1 > Red13 > Red1, and is related to the electron delocalization within the molecule and the electron withdrawing power of the substituents. The dyes were then oxidized, and Red1 and Red13, bearing an aliphatic amine, were oxidized in a reversible one electron step, to generate the radical cations. The presence of a primary aromatic amine in Or1 provokes a positive shift in the potential of the oxidation peak and shows reversible voltammetry only at scan rates above 200 mV s -1 . The ease of oxidation decreases in the order Red1 > Red13 > Or1, and is thought to relate to the detected mutagenic activity of the dyes.

Now a day graphene is a promising material for the development of high sensitivity sensing system.current status of the intrinsic mechanical properties of graphene along with properties of bulk graphene based nanocomposite is thoroughly examine. Graphene (G) is a two-dimensional material with exceptional sensing properties. In general gas sensor are produced in field effect transistor configuration on several substrate. The role of substrates on the sensor characteristics has not yet been entirely established.Graphene has gather must interest in research in recent years due to its unique mechanical, electrical, chemical & optical properties that can be developed into various applications with noval functionalities. Graphene-based gas sensor has attracted much attention in recent years due to their variety of structure, unique sensing performance, room temperature working conditions & tremendous application prospectus etc.

Hydrogen purity was studied for an EHC in presence of carbon dioxide mixture. • RWGS is the main responsible for the decreasing performance of the EHC. • Electrochemical reduction of CO2 is not influencing the performance of the EHC. • The EHC can be regenerated effectively with air bleeding as for PEM-FCs.

Silicon (Si) films were deposited on low-cost graphite substrates by the electrochemical reduction of silicon dioxide nanoparticles (nano-SiO2) in calcium chloride (CaCl2), melted at 855 °C. Cyclic voltammetry (CV) was used to analyze the electrochemical reduction mechanism of SiO2 to form Si deposits on the graphite substrate. X-ray diffraction (XRD) along with Raman and photoluminescence (PL) results show that the crystallinity of the electrodeposited Si-films was improved with an increase of the applied reduction potential during the electrochemical process. Scanning electron microscopy (SEM) reveals that the size, shape, and morphology of the Si-layers can be controlled from Si nanowires to the microcrystalline Si particles by controlling the reduction potentials. In addition, the morphology of the obtained Si-layers seems to be correlated with both the substrate materials and particle size of the feed materials. Thus, the difference in the electron transfer rate at substrate/na...

Cyclic voltammograms for the reduction of ethyl 2-bromo-3-(3 0 ; 4 0-dimethoxyphenyl)-3-(propargyloxy)propanoate (1) at glassy carbon electrodes in dimethylformamide containing tetraalkylammonium salts exhibit three prominent waves corresponding to cleavage of the carbon-bromine bond and to subsequent reduction of ethyl trans-3-(3 0 ; 4 0-dimethoxyphenyl)-prop-2-enoate (4). Controlled-potential electrolyses of 1 at potentials corresponding to reduction of the carbon-bromine bond afford 4 as the major product with an average yield of 56%. In the presence of a proton donor (1,1,1,3,3,3-hexafluoro-2-propanol), the quantity of 4 decreases slightly, and 2-(3 0 ; 4 0-dimethoxyphenyl)-3-(ethoxycarbonyl)-4-methyl-2,5-dihydrofuran (3) is obtained in moderate amount ($26%). We propose a mechanistic scheme whereby the major products are formed via a combination of one-and twoelectron processes.

Gas-diffusion electrodes are prepared with commercial Cu 2 O and Cu 2 O-ZnO mixtures deposited onto carbon papers and evaluated for the continuous CO 2 gas phase electroreduction in a filter-press electrochemical cell. The process mainly produced methanol, as well as ethanol and n-propanol. The analysis includes the evaluation of key variables with effect in the electroreduction process: current density (j= 10 to 40 mA•cm-2), electrolyte flow/area ratio (Q e /A= 1 to 3 ml•min-1 •cm-2) and CO 2 gas flow/area ratio (Q g /A= 10 to 40 ml•min-1 •cm-2), using a 0.5 M KHCO 3 aqueous solution. The maximum CO 2 conversion efficiency to liquid-phase products was 54.8% and 31.4% for Cu 2 O and Cu 2 O/ZnO-based electrodes, at an applied potential of-1.39 and-1.16 V vs. Ag/AgCl, respectively. Besides, the Cu 2 O/ZnO electrodes are expected to catalyse the CO 2 electroreduction for over 20 h. These results may provide new insights into the development of powerful electrocatalysts for reduction of CO 2 in gas phase to alcohols.

The electrochemical reduction of carbon dioxide to formic acid was performed for the first time in a pressurized filter-press cell with a continuous recirculation of the electrolytic solution (0.9 L) at a tin cathode. It was shown that the performances of the system are comparable or slightly better than that of a batch system with a smaller volume (0.05 L). The selection of proper values of both current density and CO 2 pressure allowed to achieve quite high values of faradaic efficiencies. Long-time electrolyses have shown that the system is stable and that it can allow to generate quite high concentrations of HCOOH (about 0.4 M).

This study reports new facile approach for gram-scale synthesis of graphene-like nanosheets fine powder, using glucose as precursor. Reduced graphene oxide (RGO) has been prepared in gram-scale via hydrothermal treatment of glucose. Upon increasing the vapor/liquid ratio for aqueous glucose solution within the autoclave system to 3/2, RGO-rich graphitic powder, containing small graphene oxide and amorphous carbon contents and having spherical morphology, is obtained. Then, introducing ammonia into the reaction medium resulted in the formation of pure RGO with reduced O-content and flat nanosheet-like morphology (Amm-RGO 3/2). Interestingly, few-layer graphene-like nanosheets with slight oxygen and amorphous carbon contents and few structural defects are produced when annealing Amm-RGO 3/2 at 600°C under inert atmosphere. In summary, hydrothermal treatment of aqueous solution containing just glucose and ammonia followed by moderate-temperature thermal annealing, lead to few-layer graphene-like nanosheets with good structural characteristics. This new simple and efficient approach can be of great potential in the mass production of graphene-like nanosheets.

The diradical acceptor-donor-acceptor triad 1(••), based on two polychlorotriphenylmethyl (PTM) radicals connected through a tetrathiafulvalene(TTF)-vinylene bridge, has been synthesized. The generation of the mixed-valence radical anion, 1(•-), and triradical cation species, 1(•••+), obtained upon electrochemical reduction and oxidation, respectively, was monitored by optical and ESR spectroscopy. Interestingly, the modification of electron delocalization and magnetic coupling was observed when the charged species were generated and the changes have been rationalized by theoretical calculations.

Carbon dioxide (CO2) is considered as the prime reason for the global warming effect and one of the useful ways to transform it into an array of valuable products is through electrochemical reduction of CO2 (ERC). This process requires an efficient electrocatalyst with high faradaic efficiency at low overpotential and enhanced reaction rate. Herein, we report an innovative way of reducing CO2 using copper-metal supported on titanium oxide nanotubes (TNT) electrocatalysts. The TNT support material was synthesized using alkaline hydrothermal process with Degussa (P-25) as a starting material. Copper nanoparticles were anchored on the TNT by homogeneous deposition-precipitation method (HDP) with urea as precipitating agent. The prepared catalysts were tested in a home-made H-cell with 0.5 M NaHCO3 aqueous solution in order to examine their activity for ERC and the optimum copper loading. Continuous gas-phase ERC was carried out in a solid polymer electrolyte (SPE) reactor. The 10% Cu/T...

The electrochemical reduction of carbon dioxide to formic acid was performed for the first time in a pressurized filter-press cell with a continuous recirculation of the electrolytic solution (0.9 L) at a tin cathode. It was shown that the performances of the system are comparable or slightly better than that of a batch system with a smaller volume (0.05 L). The selection of proper values of both current density and CO 2 pressure allowed to achieve quite high values of faradaic efficiencies. Long-time electrolyses have shown that the system is stable and that it can allow to generate quite high concentrations of HCOOH (about 0.4 M).

Carbon dioxide (CO2) is considered as the prime reason for the global warming effect and one of the useful ways to transform it into an array of valuable products is through electrochemical reduction of CO2 (ERC). This process requires an efficient electrocatalyst with high faradaic efficiency at low overpotential and enhanced reaction rate. Herein, we report an innovative way of reducing CO2 using copper-metal supported on titanium oxide nanotubes (TNT) electrocatalysts. The TNT support material was synthesized using alkaline hydrothermal process with Degussa (P-25) as a starting material. Copper nanoparticles were anchored on the TNT by homogeneous deposition-precipitation method (HDP) with urea as precipitating agent. The prepared catalysts were tested in a home-made H-cell with 0.5 M NaHCO3 aqueous solution in order to examine their activity for ERC and the optimum copper loading. Continuous gas-phase ERC was carried out in a solid polymer electrolyte (SPE) reactor. The 10% Cu/T...

This paper describes the exohedral N-decoration of multi-walled carbon nanotubes (MWCNTs) with NH-aziridine groups via [2+1] cycloaddition of a tert-butyl-oxycarbonyl nitrene followed by controlled thermal decomposition of the cyclization product. The chemical grafting with Ncontaining groups deeply modifies the properties of the starting MWCNTs, generating new surface microenvironments with specific base (Brønsted) and electronic properties. Both these features translate into a highly versatile single-phase heterogeneous catalyst (MW@N Az) with remarkable chemical and electrochemical performance. Its surface base character promotes the Knoevenagel condensation with superior activity to that of related N-doped and N-decorated carbon nanomaterials of the state-of-the-art; the N-induced electronic surface redistribution drives the generation of high energy surface "C" sites suitable for O 2 activation and its subsequent electrochemical reduction (ORR).

The study of the green reductant effects to produce reduced graphene oxide (rGO) has been successfully completed. The reduction of graphene oxide (GO) was carried out chemically using various reductants such as ascorbic acid (rGO-AA), gallic acid (rGO-AG), and trisodium citrate (rGO-NS). The GO was prepared using the Tour method at a temperature of 65℃ for 6 hours with potassium permanganate: graphite weight ratio 1:3.5. The results showed that rGO-AA had the highest electrical conductivity value of 755.70 S/m with a number of characteristics such as a surface area of 255.93 m 2 /g, total pore volume of 0.61 cm 3 /g, average pore diameter of 7.10 nm, ID/IG ratio of 1.93, and three graphene layers in the material nanostructure stack. Therefore, it can be concluded that the reduction of GO with ascorbic acid (rGO-AA) is the most effective in producing rGO.

A facile, postsynthetic treatment of a designed composite of pyrimidine-based porous-organic polymer and graphene (PyPOP@G) with ionic Pt, and the subsequent uniform electrodeposition of Pt metallic within the pores, led to the formation of a composite material (PyPOP-Pt@G). The pyrimidine porous-organic polymer (PyPOP) was selected because of the abundant Lewis-base binding sites within its backbone, to be combined with graphene to produce the PyPOP@G composite that was shown to uptake Pt ions simply upon brief incubation in H 2 PtCl 6 solution in acetonitrile. The XPS analysis of PyPOP@G sample impregnated with Pt ions confirmed the presence of Pt(II/ IV) species and did not show any signs of metallic nanoparticles, as further confirmed by transmission electron microscopy. Immediately upon electrochemical reduction of the Pt(II/IV), metallic Pt (most likely atomistic Pt) was observed. This approach stands out, as compared to Pt monolayer deposition techniques atop metal foams, or a recently reported atomic layer deposition (ALD), as a way of depositing submonolayer coverage of precious catalysts within the 1−10 nm pores found in microporous solids. The prepared catalyst platform demonstrated large current density (100 mA/cm 2) at 122 mV applied overpotential for the hydrogen evolution reaction (HER), with measured Faradaic efficiency of 97(±1)%. Its mass activity (1.13 A/mg Pt) surpasses that of commercial Pt/C (∼0.38 A/mg Pt) at the overpotential of 100 mV. High durability has been assessed by cyclic and linear sweep voltammetry, as well as controlled potential electrolysis techniques. The Tafel plot for the catalyst demonstrated a slope of ∼37 mV/decade, indicating a Heyrovsky-type rate-limiting step in the observed HER.

In this work, energy storage properties of mixed copper oxide wrapped by reduced graphene oxide and nitrogen-doped reduced graphene oxide were investigated. First, co-electrophoretic deposition technique was used to coat GO@CuO on nickel foam; followed by electrochemical phase transformation to rGO@Cu x O. Electron spectroscopy analyses (XPS, REELS and UPS) confirm the phase transformation and electrochemical reduction. Then, an electrophoretic deposition was carried out for coating nitrogen-doped graphene oxide on nickel foam coupled to its electrochemical reduction to the NrGO. The cathode and anode performances were studied by galvanostatic charge-discharge, cyclic voltammetry and impedance spectroscopy. The rGO@Cu x O and NrGO exhibit a favorable specific capacity of 267.2 and 332.6 C g-1 at 2 A g-1 , respectively. High electrochemical activity and elimination of polymer binders with a maximum potential of 1.6 V are among the advantages of rGO@Cu x O//NrGO electrochemical charge storage device. Furthermore, fabricated device provided a maximum specific power and specific energy of 11917.24 W kg-1 and 14.15 Wh kg-1 , respectively, with 86% capacity retention after 2000 cycles.

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The ability to capture, store, and use CO2 is important for remediating greenhouse‐gas emissions and combatting global warming. Herein, Au nanoparticles (Au‐NPs) are synthesized for effective electrochemical CO2 reduction and syngas production, using polyethylenimine (PEI) as a ligand molecule. The PEI‐assisted synthesis provides uniformly sized 3‐nm Au NPs, whereas larger irregularly shaped NPs are formed in the absence of PEI in the synthesis solution. The Au‐NPs synthesized with PEI (PEI−Au/C, average PEI Mw=2000) exhibit improved CO2 reduction activities compared to Au‐NPs formed in the absence of PEI (bare Au NPs/C). PEI−Au/C displays a 34 % higher activity toward CO2 reduction than bare Au NPs/C; for example, PEI−Au/C exhibits a CO partial current density (jCO) of 28.6 mA cm−2 at −1.13 VRHE, while the value for bare Au NPs/C is 21.7 mA cm−2; the enhanced jCO is mainly due to the larger surface area of PEI−Au/C. Furthermore, the PEI−Au/C electrode exhibits stable performance ov...

Technological advancements are leading to an upsurge in demand for functional materials that satisfy several of humankind's needs. In addition to this, the current global drive is to develop materials with high efficacy in intended applications whilst practising green chemistry principles to ensure sustainability. Carbon-based materials, such as reduced graphene oxide (RGO), in particular, can possibly meet this criterion because they can be derived from waste biomass (a renewable material), possibly synthesised at low temperatures without the use of hazardous chemicals, and are biodegradable (owing to their organic nature), among other characteristics. Additionally, RGO as a carbon-based material is gaining momentum in several applications due to its lightweight, nontoxicity, excellent flexibility, tuneable band gap (from reduction), higher electrical conductivity (relative to graphene oxide, GO), low cost (owing to the natural abundance of carbon), and potentially facile and scalable synthesis protocols. Despite these attributes, the possible structures of RGO are still numerous with notable critical variations and the synthesis procedures have been dynamic. Herein, we summarize the highlights from the historical breakthroughs in understanding the structure of RGO (from the perspective of GO) and the recent stateof-the-art synthesis protocols, covering the period from 2020 to 2023. These are key aspects in the realisation of the full potential of RGO materials through the tailoring of physicochemical properties and reproducibility. The reviewed work highlights the merits and prospects of the physicochemical properties of RGO toward achieving sustainable, environmentally friendly, low-cost, and high-performing materials at a large scale for use in functional devices/processes to pave the way for commercialisation. This can drive the sustainability and commercial viability aspects of RGO as a material.

This paper is devoted to an investigation on the methane sensing properties of graphene (G), decorated with silver nanoparticles (AgNPs), under ambient conditions. To do so, we first present an effective modification in the standard manner of decorating graphene by AgNPs. From Structural analysis of the product (AgNPs/G), it is concluded that graphene is indeed decorated by AgNPs of a mean size, 29.3 nm, aggregation-free with a uniform distribution. The so-produced material is then used, as a resistivity-based sensor, to examine its response to the presence of methane gas. Our measurements are performed at relatively low temperatures, for various silver-to-graphene mass ratios (SGMRs) and methane concentrations. To account for the effects of humidity, we have made the measurements, at room temperature, for different levels of humidity. Our results demonstrate that an increase in the SGMR enhances the response of AgNPs/G to methane with an optimum value of SGMR 12%. It is also illustrated that for ≅ methane concentrations less than 2000 ppm the maximal response increases linearly and rapidly, even at room temperature. Moreover, we demonstrate that AgNPs/G is of low limit of detection, highly stable, selective, reversible, repeatable and sensor-to-sensor reproducible, for methane sensing. The results thus promise a low-cost and simple-to-fabricate methane sensing device.

The distribution of oxygen functional groups on the surface of graphene oxide (GO) has been investigated experimentally and theoretically. Atomic layer deposition of TiO x was used to clarify the location of oxygen functional groups. We found that the oxygen functional groups are distributed in the form of islands, which is confirmed using aberration corrected transmission electron microscopy and X-ray photoelectron spectroscopy. The density functional studies further support these findings. The evolution of oxygen functional groups was also investigated with GO treated at 150, 200, 250, and 300 C. In addition, the reduction of epoxide and hydroxyl groups on the GO surface at different temperatures has been discussed in connection with ab initio molecular dynamics simulations.

The bimetallic alloy nanoparticle catalysts composed of Pd and Cu were synthesized for electrochemical reduction of CO 2. The effect of the catalyst composition on the CO 2 reduction activity and the selectivity was investigated, and at the high Pd/Cu ratio CO 2 reduction to formate rather than hydrogen evolution proceeded predominantly. The combination of Pd with Cu also changed the stability of the catalyst. By using the bimetallic catalyst, stable reduction current was obtained in the long-term electrolysis while a monometallic Pd catalyst suffered from deactivation due to poisoning by CO. These improvements are attributable to the electrical interaction between Pd and Cu. The resultant lowering shift of a d-band center reduced binding strength of CO, leading to the achievement of stable reduction of CO 2 with a small overpotential.

The chemical reduction process of graphene oxide combined with a mild and controllable thermal treatment under vacuum at 200 C for 4 hours provided a cost-effective, scalable, and high-yield route for Reduced Graphene Oxide (RGO) industrial production and became a potential candidate for producing electromagnetic interference (EMI) shielding. We investigated graphite, and RGO using Lascorbic acid and Sodium borohydride before and after thermal treatment by carefully evaluating the chemical and morphological structures. The thermally treated L-ascorbic Acid reduction route (TCRGOL) conductivity was 2.14 Â 10 3 S m À1 and total shielding efficiency (SET) based on mass loadings per area of shielding was 94 dB with about one-tenth less graphite weight and surpassing other graphene reduction mechanisms in the frequency range of 8.2-12.4 GHz, i.e., X-band, at room temperature while being tested using the waveguide line technique. The developed treatment represents valuable progress in the path to chemical reduction using a safe reducing agent and offering superior quality RGO rarely achieved with the top-down technique, providing a high EMI shielding performance.

Finding and implementing more sustainable alternatives to the fossil-dependence routes for methanol (MeOH) manufacturing is undoubtedly one of the challenges of our model of society. Some approaches can be used to convert CO 2 into MeOH as direct hydrogenation or electrochemical reduction (ER). These alternatives lead to lower natural resources consumption respect the conventional routes, but they are still found at different technological readiness levels (TRLs) and some remaining challenges need to be overtaken to achieve a carbon neutral cycle respect the conventional route, especially in the case of ER, which is currently found at its infancy. That would indicate their final industrial competitiveness in a sustainable mode. This study uses Life Cycle Assessment as the main tool in order to compare these two CO 2-based manufacture alternatives (found at different TRLs) with the fossil-route. The results allow for evaluating the potential challenges inherited to the alternative based on ER. Utilization of renewable energy is one of the most important key issues to achieve a carbon neutral product using these options. However, its benefit is neglected due to the high requirement of steam in the purification step, particularly in ER. It was demonstrated that a future scenario using ER

Carbon dioxide (CO 2) utilization alternatives for manufacturing formic acid (FA) such as electrochemical reduction (ER) or homogeneous catalysis of CO 2 and H 2 could be efficient options for developing more environmentally-friendly production alternatives to FA fossil-dependant production. However, these alternatives are currently found at different technological readiness levels (TRLs), and some remaining technical challenges need to be overcome to achieve at least carbon-even FA compared to the commercial process, especially ER of CO 2 , which is still farther from its industrial application. The main technical limitations inherited by FA production by ER are the low FA concentration achieved and the high overpotentials required, which involve high consumptions of energy (ER cell) and steam (distillation). In this study, a comparison in terms of carbon footprints (CF) using the Life Cycle Assessment (LCA) tool was done to evaluate the potential technological challenges assuring the environmental competitiveness of the FA production by ER of CO 2. The CF of the FA conventional production were used as a benchmark, as well as the CF of a simulated plant based on homogeneous catalysts of CO 2 and H 2 (found closer to be commercial). Renewable energy utilization as PV solar for the reaction is essential to achieve a carbon-even product; however, the CF benefits are still negligible due to the enormous contribution of the steam produced by natural gas (purification stage). Some ER reactor configurations, plus a recirculation mode, could achieve an even CF versus commercial process. It was demonstrated that the ER alternatives could lead to lower natural resources consumption (mainly, natural gas and heavy fuel oil) compared to the commercial process, which is a noticeable advantage in environmental sustainability terms.

Few methods are available for the routine reduction of alcohols in synthetic chemistry. These few are dominated by reduction with HI/I 2 , LiAlH 4 or Li/NH 3 and typically involve severe conditions for other functionalities and there is little research into less severe synthetic or electrochemical methods. There is also limited mechanistic or kinetic information available for these reduction methods. This leaves an interesting area for development within fundamental knowledge. The development of an effective process for the reduction of alcohols could have many applications in pharmaceutical and chemical industries along with many environmental and economical benefits. A preliminary study on a range of electrodes established an electrochemical reduction response observed for a number of water-soluble alcohols on rotating disc copper, tin and lead electrodes in 0.1 M phosphate buffers. A response was observed for ethanol, propanol, propan-2-ol and butanol on copper rotating disc electrodes in the 0.1 M phosphate buffer. Reduction of the alcohols at the copper disc electrodes was observed at pH 8.1 with the production of a limiting current plateau. The reduction was found to be continuous and reproducible. The observed limiting current was found to increase with both increasing concentration and increasing electrode rotation rate. A Koutecky-Levich study suggested the reduction of the alcohol occurred through both mass transport and kinetic processes. A discrete, reproducible response was observed for ethanol, propanol and propan-2-ol on tin rotating disc electrodes in the 0.1 M phosphate buffer electrolyte at pH 7.3. A reductive peak was observed at −1.1 V vs Ag/AgCl in cyclic voltammetry. This formation of a reductive peak suggests that the reduction becomes progressively hindered, proposed to be due to a passivating layer forming on the surface of the electrode. The charge associated with the peak is relatively invariant with alcohol concentration (in the range 7−20 mM) and with scan rate (over the range 10−500 mV s −1). In the case of ethanol, the peak charge is typically found to be in the range 2.9−3.6 C m −2 suggesting that a passivating layer of reaction products forms with an area of 8.8−10.8 Ǻ 2 for each adsorbed molecule (assuming a 2-electron process and a surface roughness factor of one). This suggests formation of iii Table of Contents iv List of Tables ix List of Figures xiv List of Symbols xix List of Abbreviations xxi Chapter 1 v 1.5 Organisation of this Thesis Chapter 2 Experimental Methods and Materials 2.1 vi 2.7.2 Phosphate Buffers 2.8 Deoxygenation of Electrolyte 2.9 Data Analysis Chapter 3 Cyclic Voltammetry Results and Discussion 3.1

Organoboron is a class of compounds widely used in organic synthesis, pharmaceuticals, material science, sensors, and so on. Therefore, the development of efficient and selective electrochemical methods to synthesize organoboron has attracted much interest as an emerging sustainable technique of organic synthesis. Here, we summarized research on electrochemical borylations, including the elec-trochemically driven borylation of arenes, alkanes, aryl, or alkyl halides, activated carboxylic acids etc., based on direct electrolysis and metal-free organocatalysis. We focus on the reaction mechanisms involved in single-electron transfer and other radical processes. We believe that this review will inspire electrochemists to discover more efficient transformations to expand this field of borylation.

ABSTRACT: Carbon capture and utilization technologies (CCU) and electrolytic hydrogen production are closely interconnected technologies and necessary for a sustainable energy system. This work describes the development of a process for room temperature co-electrolysis of CO2 and water to produce syngas, at mild pressures. The influence of several parameters in the performance of the process is reported.N/

Oxygen reduction reaction, ORR, is of significant importance for the development of new sources of energy. 1,2 So far, platinum carbon cathodes are considered as the best catalysts for this process. Nevertheless, they exhibit certain drawbacks including the high cost of Pt, a low tolerance to fuel/methanol crossover, and poor operation durability. All of these direct the attention of researchers to the development of non-noble metal or non-metal electrocatalysts, which could have a sufficient performance in ORR and could be used as replacement for Pt/C materials. 3-16 Non-metal electrocatalysts are mainly based on heteroatom-doped carbons. 13-15,17-25 So far, research efforts have focused on nonporous carbonaceous catalysts such as graphene

The tuneability of oxygen containing groups in graphene oxide (GO) that controls physicochemical properties is highly desirable for device applications. In this context, the thermally reduced graphene oxide (r-GO) powders and spin coated thin films with varying sp2/sp3 carbon network have been prepared using highly exfoliated GO (synthesized using modified Hummer's method with an innovative conjunction of lyophilisation). The additional step of lyophilisation results in the formation of highly exfoliated and monodispersed GO nanosheets as evidenced from FESEM, TEM, XRD, and Raman, FT-IR and UV-Vis spectroscopy. Spectroscopic analysis revealed the systematic evolution of r-GO with tuneable structural, optical and electrical properties as results of varying annealing temperatures (100-400 °C), due to restoration of sp2 conducting carbon network i.e., the formation of new -C═C- network and Stones-Wales defect. The tuneability of physical properties is further corroborated by change...

The foibles in extant wastewater treatment technologies release untreated nitrate and ammonia containing compounds into different potable water sources. The toxicity and fatal effects of entrained nitrate and ammonia produce lethal health consequences upon being consumed. Novel methods obtained by combining light, electrical, and chemical energy have opened new frontiers of pronounced efficiency and reduced demerits. These methods lead to the destruction of nitrate instead of just removing it by adsorption on the surface of another material. Photochemical (PC) and electrochemical (EC) reactions offer a vast scope for degrading harmful ammonia and nitrates from wastewater. The catalyzed form of these processes has been found to be meritorious over non-catalyzed techniques due to several advantages like improved efficiency, lower energy input, lower reaction time, and product selectivity towards N2 gas over nitrate and nitrite. This paper presents a review of significant research that has been performed using PC, EC, and photoelectrochemical (PEC) to remove ammonia and nitrate from wastewater. Not much research is available on the combined and simultaneous use of PC and EC oxidation and reduction processes which have immense potential as future methodologies for treating municipal and industrial wastewater to remove these toxic inorganic nitrogenous compounds. High ammonia and nitrate removal efficiencies at the laboratory scale have been reported using specific combinations of catalysts, pH, cell composition, electrodes, electrical input, and reaction time by electrochemical denitrification. However, they lack practical viability. Catalyzed photochemical processes are successful in removing ammonia and nitrate to a large extent and are practically viable if carried out using natural sunlight. Combined PC and EC, i.e., PEC oxidation and reduction processes, eliminate the occurrence of toxic intermediates and give about 90 % to 98 % conversion of ammonia and nitrate in the form of nitrogen gas.

Palladium nanoparticles (Pd NPs) were formed by electrochemical reduction of Pd(NH3)4(3+) ions entrapped by ion exchange in poly(acrylic acid) (PAA) multilayer films grown by the Sharpless "click reaction." The alkyne (PAAalk) and azide (PAAaz) groups were covalently bound to the PAA, and the catalyzed buildup of the multilayer film was performed by electrochemical reduction of Cu(2+) to Cu(+). The size of the Pd NPs formed in Au/(PAAalk)3(PAAaz)2 multilayer films by the click reaction, that is, 50 nm, is larger than that of similar Pd NPs formed in electrostatically bound Au/(PAA)3(PAH)2 nanoreactors, that is, 6-9 nm, under similar conditions. A combination of electrochemical methods and electrochemical quartz crystal microbalance, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), ellipsometry, and scanning electron microscopy has been used to follow these processes. Cyclic voltammetry of the resulting Pd NPs in a 0.1 M H2SO4 solution at 0.1 ...

Reduction graphene oxide (r-GO) lines on graphene oxide (GO) films can be prepared by a photocatalytic reduction and photothermal reduction method. A mechanism of partial GO reduction by pulsed photon energy is identified for preparing patterned rGO-GO films. The photocatalytic reduction method efficiently reduces GO at low photon energies. The successful production of a patterned rGO-GO film without damage by the photo thermal reduction method is possible when an energy density of 6.0 or 6.5 J/m2 per pulse is applied to a thin GO film (thickness: 0.45 μm). The lowest resistance obtained for a photo-reduced rGO line is 0.9 kΩ sq−1. The GO-TiO2 pattern fabricated on the 0.23 μm GO-TiO2 composite sheet through the energy density of each pulse is 5.5 J/m2 for three pulses.