Electrochemical Transformation Research Articles

Modulating water hydrogen bonding within a non-aqueous environment controls its reactivity in electrochemical transformations

Modulating water hydrogen bonding within a non-aqueous environment controls its reactivity in electrochemical transformations

Computational and Experimental Research on the Influence of Supplied Gas Fuel Mixture on High-Temperature Fuel Cell Performance Characteristics

Currently, the process of creating industrial installations is associated with digital technologies and must involve the stage of developing digital models. It is also necessary to combine installations with different properties, functions, and operational principles into a single system. Some tasks require the use of predictive modeling and the creation of “digital twins”. The main processes during the fuel cell modeling involve electrochemical transformations as well as the movement of heat and mass flows, including monitoring and control processes. Numerical methods are utilized in addressing various challenges related to fuel cells, such as electrochemical modeling, collector design, performance evaluation, electrode microstructure impact, thermal stress analysis, and the innovation of structural components and materials. A digital model of the membrane-electrode unit for a solid oxide fuel cell (SOFC) is presented in the article, incorporating factors like fluid dynamics, mass transfer, and electrochemical and thermal effects within the cell structure. The mathematical model encompasses equations for momentum, mass, mode, heat and charge transfer, and electrochemical and reforming reactions. Experimental data validates the model, with a computational mesh of 55 million cells ensuring numerical stability and simulation capability. Detailed insights on chemical flow distribution, temperature, current density, and more are unveiled. Through a numerical model, the influence of various fuel types on SOFC efficiency was explored, highlighting the promising performance of petrochemical production waste as a high-efficiency, low-reagent consumption fuel with a superior fuel utilization factor. The recommended voltage range is 0.6–0.7 V, with operating temperatures of 900–1300 K to reduce temperature stresses on the cell when using synthesis gas from petrochemical waste. The molar ratio of supplied air to fuel is 6.74 when operating on synthesis gas. With these parameters, the utilization rate of methane is 0.36, carbon monoxide CO is 0.4, and hydrogen is 0.43, respectively. The molar ratio of water to synthesis gas is 2.0. These results provide an opportunity to achieve electrical efficiency of the fuel cell of 49.8% and a thermal power of 54.6 W when using synthesis gas as fuel. It was demonstrated that a high-temperature fuel cell can provide consumers with heat and electricity using fuel from waste from petrochemical production.

In-situ groundwater remediation of contaminant mixture of As(III), Cr(VI), and sulfanilamide via electrochemical degradation/transformation using pyrite

Electrochemical advanced oxidation processes (EAOPs) are effective in removing persistent contaminants from groundwater. However, their practical applicability depends significantly on various site-specific characteristics. Therefore, the primary objective of this investigation was to study the feasibility of EAOPs and pyrite, which is a sulfide mineral, to effectively remove the mixture of arsenic (As (III)), chromium (Cr (VI)), and sulfanilamide in groundwater. We conducted a comparison of three systems: (1) EAOP alone, (2) pyrite alone, and (3) a combined EAOP and pyrite system. In EAOP alone, sulfanilamide was effectively oxidized (80%), while the electrochemical transformation of As(III)/Cr(VI) into As(V)/Cr(III) was limited. In just the pyrite system, As(III), Cr(VI), and sulfanilamide were adsorbed onto the surface of pyrite (60%, 20%, and 18%). Neither the EAOP nor the pyrite system alone could effectively treat the contaminants mixture. Nonetheless, the combined system completely removed As(III), Cr(VI), and sulfanilamide by the synergistic reaction. This could be attributed to the formation of green rust, a natural adsorbent mineral produced as a reaction of dissolved iron, generated via electrochemical pyrite oxidation, with the groundwater electrolyte (e.g., CO3 or SO4). This system harmonized the combined approach of EAOP and pyrite to effectively eliminate both organic and inorganic contaminants. Environmental implicationA paper proposed electrochemical oxidation (EO) with pyrite to remove both organic and inorganic contaminants from groundwater. The removal performance of the combined system was evaluated, and the synergistic mechanism was revealed. The combination of EO and pyrite with synergistic removal effectively removed the mixture of both contaminants. This could be attributed by the formation of green-rust by electrochemical activation for pyrite. Compared to the single system of EO and pyrite alone, the combined system with EO and pyrite improved removal performance. Results suggested that the combined system could be used for green groundwater remediation.

Electrochemical C−H deuteration of pyridine derivatives with D2O

Herein, we develop a straightforward, metal-free, and acid-/base-free electrochemical C4-selective C − H deuteration of pyridine derivatives with economic and convenient D2O at room temperature. This strategy features an efficient and environmentally friendly approach with high chemo- and regioselectivity, affording a wide range of D-compounds, such as pyridines, quinolones, N-ligands and biorelevant compounds. Notably, the mechanistic experiments and cyclic voltammetry (CV) studies demonstrate that N-butyl-2-phenylpyridinium iodide is a crucial intermediate during the electrochemical transformation, which provides a general and efficient way for deuteration of pyridine derivatives.

Synergistic impact of dual active sites in Nb-Fe2P nanoparticles on electrocatalytic nitrate reduction with high selectivity

The electrochemical transformation of nitrate into ammonia offers a promising alternative to the traditional Haber-Bosch process. The nitrate reduction reaction (NO3–RR) involves complex multi-electron/proton processes and faces competition from hydrogen evolution reactions, leading to low Faraday efficiency and diminished ammonia production. This study introduces carbon-supported niobium-doped iron phosphide nanoparticles (Nb-Fe2P) electrocatalysts, synthesized using deep eutectic solvent (DES). These electrocatalysts achieved an exceptional ammonia yield of 9.7 mg h−1 cm−2 and a Faraday efficiency of 95.8 % in the NO3–RR. Both experimental and theoretical studies reveal that the dual active sites of Fe and Nb significantly enhance the generation of active hydrogen and expedite the utilization of nitrogen-containing intermediates. This innovative approach, focusing on active hydrogen balance, offers a strategic pathway for developing highly efficient NO3–RR electrocatalysts by promoting the dissociation of H2O.

Effect of Fe and Zn co-doping on LiCoPO4 cathode materials for High-Voltage Lithium-Ion batteries

Lithium cobalt phosphate (LiCoPO4) has great potential to be developed as a cathode material for lithium-ion batteries (LIBs) due to its structural stability and higher voltage platform with a high theoretical energy density. However, the relatively low diffusion of lithium ions still needs to be improved. In this work, Fe and Zn co-doped LiCoPO4: LiCo0.9-xFe0.1ZnxPO4/C is utilized to enhance the battery performance of LiCoPO4. The electrochemical properties of LiCo0.85Fe0.1Zn0.05PO4/C demonstrated an initial capacity of 118 mAh/g, with 93.4 % capacity retention at 1C after 100 cycles, and a good capacity of 87 mAh/g remained under a high current density of 10C. In addition, the diffusion rate of Li ions was investigated, proving the improvement of the materials with doping. The impedance results also showed a smaller resistance of the doped materials. Furthermore, operando X-ray diffraction displayed a good reversibility of the structural transformation, corresponding to cycling stability. This work provided studies of both the electrochemical properties and structural transformation of Fe and Zn co-doped LiCoPO4, which showed that 10 % Fe and 5 % Zn co-doping enhanced the electrochemical performance of LiCoPO4 as a cathode material in LIBs.

Recent Advances in the Electrochemical Defluorinative Transformations of C—F Bonds

Comprehensive SummaryOrganic fluorine compounds are ubiquitous and pivotally important organic molecules, yet their activation and transformation have long been a formidable challenge due to the high energy and low reactivity of C—F bonds. Organic electrosynthesis, an environmentally benign synthetic method in organic chemistry, enables a myriad of chemical transformations without the need for external redox reagents. In recent years, organic electrochemistry has emerged as a powerful tool for achieving the activation and transformation of C—F bonds in fluorine‐containing compounds. This review aims to succinctly recapitulate the latest advancements in the electrochemical defluorinative transformations of C—F bonds and to delve into the reaction design, mechanistic insights, and developmental prospects of these methods. Key ScientistsIn 1959, Lund was the first to pioneer the electroreduction of CF3 to CH3 group. Electrochemistry has lately provided new opportunities for efficient conversion of organic fluorides. In 2020, Zhou and coworkers discovered the electrochemical defluorinative carboxylation of α‐CF3 alkenes. Lambert and colleagues reported electrophotocatalytic defluorinative amination of aryl fluorides. Electrochemical hydrodefluorination of trifluoromethylketones was developed by Lennox and coworkers in 2021. In the same year, Wang and Guo disclosed electrochemical radical defluorinative alkylation of α‐CF3 alkenes with Katritzky salts as the alkyl radical precursors. Subsequently, Wu and Liao described a transition‐metal‐free, site‐selective C—F arylation of polyfluoroarenes with (het)arenes using paired electrophotocatalysis. In 2023, numerous efforts were made to achieve electrochemical C—F bond activation. Xia and Guo developed an organoboron‐controlled method for the chemoselective electrochemical sequential (deutero)hydrodefluorination of trifluoroacetamides.

Electrochemically Driven Transformation of Olivine LiFePO4 to Olivine NaFePO4 in Cells with Sodium Anode and Carbonate Electrolyte

AbstractThe direct electrochemical transformation of commercial LiFePO4 to NaxFePO4 olivine in a Na||LiFePO4 electrochemical cell with sodium electrolyte has been studied. Electrolytes containing 1 M of NaClO4 in ethylene carbonate (EC), dimethyl carbonate (DMC) and fluoroethylene carbonate (FEC) have been probed, and in the solvents with the ratio of EC:DMC:FEC=0.4:0.5:0.1 by volume, maximal values of the specific capacity (113 mAh g−1) with good cycling stability and maximal discharge currents are achieved upon sodiation. To determine the composition of the cathode material and utilization factor of LiFePO4, the dependence of open circuit voltage on specific capacity has been investigated. The general formula of the sodiation product can be written as Na0.88FePO4. Its theoretic specific capacity may be estimated as 135 mAh g−1. The composition of the products obtained is supported by XRD analysis, which suggests that in discharged cathodes, Coulombic influence of LiFePO4 crystallites on neighboring NaxFePO4 crystallites may enlarge the unit cell of the former and reduce its size of the latter. Probably, shrinkage in the presence of LiFePO4 stabilizes the olivine structure of NaxFePO4 and prevents its transformation from electrochemically active olivine to inactive maricite.

Sequential Paired Electrochemical Transformation of Styrene Oxide via Anodic Meinwald Rearrangement and Cathodic Nitromethylation in an Electrochemical Flow Reactor with Catalytic Electrical Input

Sequential Paired Electrochemical Transformation of Styrene Oxide via Anodic Meinwald Rearrangement and Cathodic Nitromethylation in an Electrochemical Flow Reactor with Catalytic Electrical Input

Polyoxometalate and ammonium polyphosphate induced bimetallic tungsten-based phosphides for electrocatalytic hydrogen production

Tungsten-based phosphide has gained significant traction in the field of electrocatalytic hydrogen evolution on account of its platinum-like characteristics, cost-effectiveness and exceptional electrical conductivity. In this work, bimetallic phosphide (WP/WCoP2@C) was prepared for hydrogen evolution reaction (HER) via high-temperature annealing and in situ phosphating procedure using the green phosphorus source ammonium polyphosphate (APP) without no toxic substances generated. WP/WCoP2@C exhibits satisfactory catalytic hydrogen evolution activity, with the overpotentials in acidic and alkaline environments of 151 and 138 mV, respectively, at current density reaching 10 mV cm−2. Moreover, WP/WCoP2@C shows favorable stability in the acid-base electrolytes for 36 h. This work provides experimental ideas for the green clean synthesis of tungsten-based phosphides for electrochemical small molecules transformation for sustainable energy generation.

Regulation of Catalyst Immediate Environment Enables Acidic Electrochemical Benzyl Alcohol Oxidation to Benzaldehyde.

Electrocatalytic alcohol oxidation in acid offers a promising alternative to the kinetically sluggish water oxidation reaction toward low-energy H2 generation. However, electrocatalysts driving active and selective acidic alcohol electrochemical transformation are still scarce. In this work, we demonstrate efficient alcohol-to-aldehyde conversion achieved by reticular chemistry-based modification of the catalyst's immediate environment. Specifically, coating a Bi-based electrocatalyst with a thin layer of metal-organic framework (MOF) substantially improves its performance toward benzyl alcohol electro-oxidation to benzaldehyde in a 0.1 M H2SO4 electrolyte. Detailed analysis reveals that the MOF adlayer influences catalysis by increasing the reactivity of surface hydroxides as well as weakening the catalyst-benzaldehyde binding strength. In turn, low-potential (0.65 V) cathodic H2 evolution was obtained through coupling it with anodic benzyl alcohol electro-oxidation. Consequently, the presented approach could be implemented in a wide range of electrocatalytic oxidation reactions for energy-conversion application.

Unraveling the Electrocatalytic Activity in HMF Oxidation to FDCA by Fine-Tuning the Degree of NiOOH Phase Over Ni Nanoparticles Supported on Graphene Oxide.

The development of an efficient electrocatalyst for HMF oxidation to FDCA has been in the early stages. Herein, the NiNPs/GO-Ni-foam is fabricated as an electrocatalyst for FDCA production. However, the electrocatalytic performance of the untreated NiNPs/GO-Ni-foam is observed with moderate Faradaic efficiency (FE) (73.0%) and FDCA yield (80.2%). By electrochemically treating the NiNPs/GO-Ni-foam in an alkaline solution with positive potential at different treatment durations, the degree of NiOOH on metal surfaces is changed. The distinctive electrocatalytic activity obtained when using the different NiOOH degrees allows to understand the crucial impact of NiOOH species in HMF electrooxidation. Enhancing the portion of the NiOOH phase on the electrocatalyst surface improves electrocatalytic activity in terms of FE and FDCA yield up to 94.8±4.8% and 86.9±4.1%, respectively. Interestingly, as long as the NiOOH portion on the electrocatalyst surface is preserved or regenerated, the electrocatalyst performance can be intact even after several catalytic cycles. The theoretical study via density functional theory (DFT) also agrees with the experimental observations and confirms that the NiOOH phase facilitates the electrochemical transformation of HMF to FDCA through the HMFCA pathway, and the potential limiting step of the overall reaction is the oxidation of FFCA to FDCA.

Efficient electroreduction of carbon dioxide to formate enabled by bismuth nanosheets enriched dual [formula omitted] vacancy

The electrocatalytic reduction of carbon dioxide (CO2ER) into formate presents a compelling solution for mitigating dependence on fossil energy and green utilization of CO2. Bismuth (Bi) has been gaining recognition as a promising catalyst material for the CO2ER to formate. The performance of Bi catalysts (named as Bi-V) can be significantly improved when they possess single metal atom vacancy. However, creating larger-sized metal atom vacancies within Bi catalysts remains a significant challenge. In this work, Bi nanosheets with dual VBi0 vacancy (Bi-DV) were synthesized utilizing in situ electrochemical transformation, using BiOBr nanosheets with triple vacancy associates (VBi″′VO···VBi″′, VBi″′ and V•• O denote the Bi3+ and O2− vacancy, respectively) as a template. The obtained Bi-DV achieved higher CO2ER activity than Bi-V, showing Faradaic efficiency for formate production of >92% from -0.9 to -1.2 VRHE in an H-type cell, and the partial current density of formate reached up to 755 mA/cm2 in a flow cell. The comprehensive characterizations coupled with density functional theory calculations demonstrate that the dual VBi0 vacancy on the surface of Bi-DV expedite the reaction kinetics toward CO2ER, by reducing the thermodynamic barrier of *OCHO intermediate formation. This research provides critical insights into the potential of large atom vacancies to enhance electrocatalysis performance.

Iron phosphide nanoparticles anchored on N-doped carbon as efficient electrocatalysts for nitrate reduction reaction

Electrochemical transformation nitrate to ammonia at ambient conditions is a green alternative approach to the conventional Haber-Bosch process, while suffering from a restricted ammonia yield rate owing to the multi-step electron and proton transfer. Herein, we reported a quintessential bubble-like iron phosphides nanoparticles anchored on N-doped carbon framework (FeP@NC) electrocatalyst for nitrate reduction reaction (NO3RR). The FeP@NC catalyst exhibits 93.12 % NH3 faradaic efficiency (FE) at −0.5 V with the yield rate of 626.07 mmol h−1 gcat−1, superior over these for Fe@NC. DFT calculations indicate that the phosphorization promotes the absorption of NO3− and following hydrogenation, beneficial for NO3RR. This study provides a reference of transition metal phosphides for efficient NO3− removal and conversion.

Evolution of α-V2O5 into electrochemically transformed NaV3O8 structure: Structural changes and supercapacitor application

Nowadays, cost-effective and environmentally friendly supercapacitors (SCs) with high energy and power densities are gaining significant research attention since they could broaden the application of capacitors. The present study demonstrates a low-cost green synthesis technique to prepare the α-V2O5 phase using Aloe Vera leaf extract. X-ray diffraction technique confirmed the formation of the orthorhombic α-V2O5 phase. The prepared α-V2O5 was employed as an electrode material for SC application. During an electrochemical cyclic voltammetry test in Na2SO4 electrolyte, Na+ ions intercalation and de-intercalation processes resulted in a phase transformation of α-V2O5 to NaV3O8. Structural transformation (i.e., orthorhombic to monoclinic crystal structure) and morphological changes were also observed during the electrochemical phase conversion process. This electrochemical phase transformation process improved the overall supercapacitive performance of the α-V2O5 material. Such electrochemically converted NaV3O8 displayed a maximum specific capacitance of 640.1 F g−1 at 0.5 A g−1 with a long cyclic stability. Furthermore, the AC // NaV3O8 asymmetric SC coin cell device delivered a maximum energy density of 62.6 Wh kg−1 and a power density of 7.3 kW kg−1 along with an excellent cycling stability of ∼81 % over 5000 GCD cycles.

Regio- and Stereoselective Synthesis of 3-Selenylazaflavanones and 3-Selenylflavanones via Electrochemically Facilitated Selenylation Cascade.

Herein, an oxidant- and metal-free electrochemical selenylation reaction of chalcones with diselenides for the synthesis of 3-selenylazaflavanones and 3-selenylflavanones at room temperature was reported. The method proceeded under mild conditions, exhibited a broad substrate scope, and provided the selenylated products in moderate to excellent yields with high regio- and stereoselectivity. The reaction could also be readily scaled up with high efficiency. Detailed mechanistic studies through control experiments disclosed that a selenium-based radical might participate in this electrochemical transformation.

Electrochemical Ni‐Catalyzed Decarboxylative C(sp3)−N Cross‐Electrophile Coupling

AbstractA new electrochemical transformation is presented that enables chemists to couple simple alkyl carboxylic acid derivatives with an electrophilic amine reagent to construct C(sp3)−N bond. The success of this reaction hinges on the merging of cooperative electrochemical reduction with nickel catalysis. The chemistry exhibits a high degree of practicality, showcasing its wide applicability with 1°, 2°, 3° carboxylic acids and remarkable compatibility with diverse functional groups, even in the realm of late‐stage functionalization. Furthermore, extensive mechanistic studies have unveiled the engagement of alkyl radicals and iminyl radicals; and elucidated the multifaceted roles played by iPr2O, Ni catalyst, and electricity.

Electrochemical Ni-Catalyzed Decarboxylative C(sp3 )-N Cross-Electrophile Coupling.

A new electrochemical transformation is presented that enables chemists to couple simple alkyl carboxylic acid derivatives with an electrophilic amine reagent to construct C(sp3 )-N bond. The success of this reaction hinges on the merging of cooperative electrochemical reduction with nickel catalysis. The chemistry exhibits a high degree of practicality, showcasing its wide applicability with 1°, 2°, 3° carboxylic acids and remarkable compatibility with diverse functional groups, even in the realm of late-stage functionalization. Furthermore, extensive mechanistic studies have unveiled the engagement of alkyl radicals and iminyl radicals; and elucidated the multifaceted roles played by i Pr2 O, Ni catalyst, and electricity.

Effect of Surface Roughness and Chemical Composition of Metastable Austenitic Stainless Steels on Electrochemical Polishing-Induced Martensitic Transformation

Herein, we analyzed the martensitic transformation kinetics during electrochemical polishing (EP) for stainless steel specimens with varying surface roughness and austenite stability. Martensite fraction measurement demonstrated that specimens with higher surface roughness and lower austenite stability exhibited relatively higher levels of martensitic transformation. To understand these phase transformation characteristics, the amount of charge build-up on the specimen surface during EP was calculated using COMSOL Multiphysics simulations for specimens with different surface roughness. The effect of charge build-up-induced stress was analyzed using previously published first-principles calculations. We found that specimens with higher surface roughness accumulated more charge build-up, resulting in greater stress and a martensitic transformation driving force. Furthermore, the critical energy required for the martensitic transformation was calculated using Thermo-Calc for specimens with different austenite stabilities. We demonstrated that the martensitic transformation kinetics during EP could be explained in terms of austenite stability, similar to the stress-induced martensitic transformation.Graphical

Design principles of heterointerfacial redox chemistry for highly reversible lithium metal anode

High electrochemical reversibility is required for the application of high-energy-density lithium (Li) metal batteries; however, inactive Li formation and SEI (solid electrolyte interface)-instability-induced electrolyte consumption cause low Coulombic efficiency (CE). The prior interfacial chemical designs in terms of alloying kinetics have been used to enhance the CE of Li metal anode; however, the role of its redox chemistry at heterointerfaces remains a mystery. Herein, the relationship between heterointerfacial redox chemistry and electrochemical transformation reversibility is investigated. It is demonstrated that the lower redox potential at heterointerface contributes to higher CE, and this enhancement in CE is primarily due to the regulation of redox chemistry to Li deposition behavior rather than the formation of SEI films. Low oxidation potential facilitates the formation of the surface with the highly electrochemical binding feature after Li stripping, and low reduction potential can maintain binding ability well during subsequent Li plating, both of which homogenize Li deposition and thus optimize CE. In particular, Mg hetero-metal with ultra-low redox potential enables Li metal anode with significantly improved CE (99.6%) and stable cycle life for 700 cycles at 3.0 mA cm-2. This work provides insight into the heterointerfacial design principle of next-generation negative electrodes for highly reversible metal batteries.