Potential Electrolysis Research Articles

Ab initio molecular dynamics study of hydroxyl positioning in butanediol and its impact on deep eutectic solvent structure

Electrolytes play a crucial role in enhancing the performance of energy storage devices, including batteries and supercapacitors. However, traditional electrolytes, such as aqueous solutions, organic solvents, and ionic liquids, exhibit inherent limitations and challenges. Deep eutectic solvents have recently emerged as promising alternatives due to their environmentally friendly nature and favorable properties. Despite their widespread applications in various domains, their potential as electrolytes remains relatively underexplored. This study investigates three distinct types of deep eutectic solvents derived from different isomers of butanediols combined with choline chloride. Ab initio molecular dynamics simulations are employed to analyze the microstructure of these deep eutectic solvents, focusing on non-covalent electrostatic interactions, hydrogen bonding patterns, and vibrational spectra. The results reveal significant differences in the structural configuration of hydrogen bond acceptors and hydrogen bond donors and their interactions within the deep eutectic solvents. Specifically, the positioning of functional groups in hydrogen bond donors significantly impacts the hydrogen bonding network and the interaction with monoatomic ions. Moreover, the vibrational spectra analysis highlights the existence of hydrogen bonds involving stretching modes of the OH group, as evidenced by redshift deviations. Overall, this study provides valuable insights into the unique features of deep eutectic solvents as potential electrolytes for energy storage applications. The comprehensive analysis of their microstructure and vibrational properties enhances our understanding of deep eutectic solvent utilization and opens avenues for further research in sustainable energy storage.

Rational design of porous vanadium-based alloys modified with a Ni-Cu-Mo coating for alkaline water electrolysis

The development of a hydrogen evolution catalyst with both catalytic activity and stability is critical for hydrogen production from electrolytic water. Herein, a V-based porous alloy was prepared via high-energy ball milling and solid-state sintering. Then, the V-based porous alloy was modified with a Ni-Cu-Mo ternary alloy coating by direct current electrodeposition to obtain a composite hydrogen evolution cathode with high hydrogen evolution activity. The substrate has a certain hydrogen storage capacity combined with a high-activity Ni-Cu-Mo coating. The composite hydrogen evolution cathode exhibited high electrocatalytic activity toward the HER. It can afford a lower overpotential of 93 mV and a smaller Tafel slope of 97.4 mV/dec with a current density of 10 mA/cm2 in 1.0 M KOH. The composite hydrogen evolution cathode demonstrated outstanding stability after 2000 cycles and good durability after intermittent electrolysis for 20 h. Hydrogen protons can protect the components of the cathode composite from dissolution during discontinuous constant potential electrolysis. The composite hydrogen evolution cathode also exhibited a strong catalytic capacity for hydrogen evolution during intermittent electrolysis under alkaline conditions.

Electrocatalytic Properties of meso‐ Perfluorinated Metallo Corroles for the Reduction of CO2

Corrole, a contracted tetrapyrrolic macrocycle has been also used to design molecular for the CO2 reduction. The electrochemical activity towards CO2 reduction can rival those of their porphyrin analogues. However, the catalytic activity of the metallocorrole is initiated at the corresponding MII/I couple. Accordingly, a catalytic current in presence of CO2 with cobalt corrole appears when the CoI species is generated. We have designed an electron deficient A2B corrole holding two ‐CF3 groups and a benzonitrile in the meso positions and its cobalt complex (1). We reasoned that these groups could shuffle the redox potentials to reach the M(I) oxidation states at more positive values thereby lowering the overpotential for the catalytic CO2 reduction. Our results clearly show that catalyst 1 when adsorbed on a carbon electrode, shows the most favourable catalytic performance for CO production, achieving an efficiency of 85% with a current density of ‐1.5 mA cm‐2 at ‐1.0 V vs NHE. The current densities of controlled potential electrolysis with increasing amount of KHCO3, were found to increase more than one order of magnitude with the formation of MeOH.

Cathode Electrochemical Behavior of Aluminum Electrolysis in NaF-NaCl Based Molten Salt

Selective and efficient electrochemical analytical methods for the depositing process of metal aluminum are significant and necessary. The electrochemical measurement methods are based on the means of cyclic voltammetry, square wave voltammetry and constant potential electrolysis. The above methods are used to analyze the depositing process of metal aluminum in NaF-NaCl-Al2O3 and NaF-NaCl-NaAlO2 molten salt. Cyclic voltammetry analysis showed that Al3+ ions were reduced to metal aluminum through two consecutive steps. From the analysis of square wave voltammetry curve, the main reaction on the electrode was the reduction of metal sodium in the NaF-NaCl system, and the electron transfer number of the reaction was 0.80. With the addition of NaAlO2 and Al2O3 in the electrolyte, the electron transfer numbers of the two reduction steps were about 3.0. The process of reduction of Al3+ ions to aluminum was further proved by the analysis of the electrolysis curve at constant potential. The diffusion rate of Al3+ions and the rate of Al3+ reduction reaction increased with the addition of NaAlO2 and Al2O3 and the change of the potential.

The Use of the Mannich Reaction toward Amino‐Based Anthraquinone Applied in Aqueous Redox Flow Battery

A water‐soluble anthraquinone derived from alizarin, 3HAAQ, is introduced as the redox‐active material in a negative potential electrolyte (anolyte) for aqueous redox flow batteries operating at pH 14. The synthesis of 3HAAQ is carried out using the Mannich reaction, which significantly improves the solubility of the new compound, an important factor for its use in RFB. Pairing with potassium ferri/ferrocyanide positive electrolyte, this flow battery exhibits an open‐circuit voltage of 1.24 V and maintains nearly 80% of the theoretical capacity at 40 mA cm−2 current density.

Avseed Battery: Environmentally Friendly Battery Innovation as Electrolytes in Dry Batteries

Energy is a fundamental force driving transformative processes across various domains. It is perpetual and adheres to the law of energy conservation, remaining indestructible. However, the challenge lies in the finite nature of conventional energy sources, which convert energy for intended purposes and cater to diverse needs, often escalating the overall cost. Among the commonly employed energy sources, batteries play a pivotal role. This study explores the viability of avocado seeds as potential electrolytes in dry batteries. The objectives are to assess the effectiveness of avocado seeds as electrolytes and to investigate the impact of solution concentration and composition on the generated electrical energy. A dry element battery, known for converting chemical energy into electrical energy through Redox (Reduction-Oxidation) electrochemical reactions, serves as the experimental focus. Using a quantitative approach with laboratory experiments, five treatments were administered, featuring different ratios (1:1, 1:2, 1:3), a negative control with avocado seeds, and a positive control with salt. The bio-battery effectiveness assessment revealed that the P4 composition (negative control with avocado seeds) exhibited the highest initial voltage of 3.4 V and an extended runtime of 156 hours. In summary, this research underscores the potential of avocado seeds as electrolytes in dry batteries, supported by observations of voltage levels and ignition times.

Degradation modeling in solid oxide electrolysis systems: A comparative analysis of operation modes

To fully realize the potential of solid oxide electrolysis (SOE) systems, improvements in long-term durability and scalability are required. Investigating and comparing different degradation mechanisms under different conditions is crucial. A multi-scale cell to system level time-dependent simulation framework for SOE systems including various degradation phenomena is presented. Galvanostatic, Potentiostatic, and Potentio-Galvanostatic operation, a combination of the two previous modes, are investigated. The time and space evolution of various performance and degradation parameters are compared. Potentio-Galvanostatic operation consistently maintains stable efficiency throughout its lifetime. Near thermoneutral condition is maintained in Potentiostatic and Potentio-Galvanostatic operations, while degradation eventually leads to exothermic operation in Galvanostatic mode. Cathode overpotential is higher in Galvanostatic operation, while in Potentio-Galvanostatic operation, it drops over time as the temperature increases. After 25,000 h of operation under specified conditions, the area-specific resistance (ASR) experiences a 51% and 62% increase in Galvanostatic and Potentiostatic operations, respectively, while Potentio-Galvanostatic operation results in only a 4% increase compared to the beginning of life. Interconnect oxidation is most pronounced in Potentio-Galvanostatic mode, highlighting the need for high-quality steels and coatings in this operation strategy. Over time, in Galvanostatic operation, the current density shifts from being highest at the inlet towards the outlet.

Separation of uranium from lanthanides (La, Ce, Nd) and purification of waste salt via aluminum electrodes with different structures in LiCl-KCl eutectic

Aluminum is an ideal cathode material for the pyrochemical reprocessing of spent nuclear fuels. However, there is a lack of large-scale experiments to further assess its performance. Here we designed several Al electrodes with sheet, rod, and porous morphologies, and employed them in separating actinides (An) from lanthanides (Ln) and purifying the waste salts in about 500 g of LiCl-KCl eutectic melt at 773 K. By applying a constant potential of −1.2 V vs. Ag/AgCl, U can be separated from Ln (La, Ce, and Nd) by forming Al-U alloys consisting of Al3U and Al4U with high separation factors and current efficiency. Among all Al electrodes used in our experiments, the porous-shaped ones show the fastest electrochemical reaction rate, and hence only 56 h were required to achieve the separation. Subsequently, the purification of the waste salts from U-Ln separation was conducted via constant potential electrolysis at −1.5 V vs. Ag/AgCl on porous-shaped Al electrodes. About 99.9 % of Ln was extracted via forming Al-Ln alloys, leaving a purified electrolyte that can be reused. In all, about 17 g of U metals and 1 kg of waste salts were successfully reprocessed in our large-scale experiments, which envisions the feasibility of applying Al electrodes in engineering-scale pyrochemical reprocessing.

Uncertainty Assessment of Carbon Monoxide in Exhaust Gas Based on Fixed Potential Electrolysis

Uncertainty Assessment of Carbon Monoxide in Exhaust Gas Based on Fixed Potential Electrolysis

Immune checkpoint inhibitors (ICI): From cancer killers to electrolyte disruptors.

e24146 Background: Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment. Cancer patients, especially lung cancer (LCa), are at an increased risk of developing electrolyte imbalance due to several etiologies such as poor nutrition, paraneoplastic syndromes, etc. It is vital to address electrolyte disturbances with the use of ICIs. Objective: The study aims to understand the relationship between ICIs and electrolyte disturbance in LCa patients. Methods: TrinetX, a global federated research network, provides a dataset of electronic medical records from different healthcare organizations (HCOs), was utilized. Initial query was made to isolate patients with LCa stages 2-4. The 2 groups were based on the presence or absence of IO (atezolizumab, durvalumab, pembrolizumab, nivolumab, ipilimumab). Further, propensity score matching (PSM) was carried out to match age, sex, race, chronic kidney disease, diarrhea. Compare outcome analytic function was utilized to map the co-relation with electrolyte imbalance. Results: 41,818 patients were identified, out of which 12.37% (n = 5172) patients received immunotherapy at some point in their cancer treatment. There was no statistical difference in age (65.9 ± 10.3 vs 65.9 ± 11.3, p = 0.8608) as well as gender in both groups. Caucasians (69% vs 66% for Causians (p < 0.0001)) were the predominant race in both groups and were more likely to receive immunotherapy compared to African Americans (12% vs 14% in AA (p = 0.0004)). Diarrhea (30% vs 9%, p < 0.0001) and Chronic kidney disease (CKD) (18% vs 8%, p < 0.0001) were predominantly seen in IO group. Prior to matching, hypomagnesemia (HypoMg) (10.47% vs 5.85%, p < 0.0001), hypocalcemia(HypoCa) (3.36% vs 2.03%, p < 0.0001), hypokalemia (HypoK) (16.91% vs 11.02%, p < 0.0001), hyperkalemia (HyperK) (7.69% vs 4.88%, p < 0.0001), hyponatremia (HypoNa) (16.82% vs 10.66%, p < 0.0001) and hypercalcemia (HyperCa) (5.26% vs 3.05%, p < 0.0001) were seen higher in IO group while hypermagnesemia (HyperMg) (2.04% vs 2.62%, p = 0.0150) was more seen in the non IO group, with no significant difference in hypernatremia (HyperNa) (2.34% vs 1.95%, p = 0.0634). After PSM, HypoMg (10.48% vs 7.01%, p < 0.0001), HypoK (16.92% vs 12.64%, p < 0.0001), HyperK (7.69% vs 6.26%, p = 0.0060), HypoNa (16.80% vs 11.56%, p < 0.0001) and HyperCa (5.26% vs 3.06%, p < 0.0001) were seen more in IO group, while HyperMg (2.04% vs 2.67%, p = 0.0399) was higher in non IO and there was no significant difference for HypoCa (3.36% vs 2.77, p = 0.0829) and HyperNa (2.34% vs 1.89%, p = 0.1135). Conclusions: Our study demonstrated that there is correlation between ICI use and electrolyte imbalance. Providers should be vigilant about the potential electrolyte abnormalities when treating patients with ICI therapy.

Electrodes composited by bisbenzimidazole silver(I) coordination polymers as electrocatalysts for hydrogen evolution and H2O2-sensing

Two new silver(Ⅰ) coordination polymers (CPs) {[Ag2(p-HMOPhIDC)(BBP)](H2O)}n (1), {[Ag2(m-HMOPhIDC)(BBP)](H2O)}n (2) (BBP = 1,3-[bis(2,2′-benzimidazole)] propane, p-H3MOPHIDC = 2-(4-methoxyphenyl)–2H-imidazole-4,5-dicarboxylic acid, m-H3MOPHIDC = 2-(3-methoxyphenyl)–2H-imidazole-4,5-dicarboxylic acid), were prepared under hydrothermal condition and structurally characterized. The CPs 1–2 both exhibit binuclear 1D “square waveform” chain structures. Structural analysis shows that the two silver ions in CP 1 are crystallographically independent but chemically identical; whereas the two silver ions in CP 2 are crystallographically independent and chemically different. Electrocatalytic hydrogen evolution reaction (HER) of carbon paste composite electrodes (CPCEs 1–2) prepared by mixing graphite powder with coordination polymers was investigated by variable temperature linear sweep voltammetry (VT-LSV), controlled potential electrolysis (CPE) and electrochemical impedance spectroscopy (EIS) in 0.5 M H2SO4 electrolyte. It was found that the overpotential η10293K of CPCEs 1–2 positively shifted 449 and 172 mV compared with sCPCE (−966 mV), and the Tafel slope of sCPCE and CPCE 1–2 were 276, 160 and 226 mV dec-1, respectively. The results proved that CPCEs 1–2 could effectively catalyze and accelerate the HER behavior. The higher HER activity of the CPCE 1 than CPCE 2 can be attributed to the fact that CP 1 contains more three-coordinated silver ions. Moreover, the recognition performance of CPCEs 1–2 for H2O2 was further studied by chronoamperometry in 0.2 M phosphate buffer solution (PBS, pH = 6). The two sensors can detect H2O2 in a linear range from 0.5 μM to 4 mM with a detection limit of 128 µM for CPCE 1 and 27.1 µM for CPCE 2 at a signal-to-noise ratio of 3, and also revealed long-term stability and good selectivity.

Electrocatalytic facets of a newly designed cobalt(III) complex towards sustainable hydrogen evolution

A hybrid cobalt complex (C7H10ON)[Co(L)2].CH3OH (Co-complex) bearing an organic cation and anionic cobalt complex has been designed, synthesized, and structurally characterized. The tridentate chelator, 2-((2-hydroxybenzylidene)amino)-4-methylphenol (H2L), was prepared by the condensation reaction between salicylaldehyde and 4-methyl-2-amino phenol. Crystal structure analysis reveals a slight distortion in the octahedral coordination geometry of the cobalt(III) centre. This complex was evaluated in the hydrogen evolution reaction (HER) using a glassy carbon working electrode in acetonitrile (ACN), using tBu4NClO4 as the supporting electrolyte. The catalyst exhibited heightened catalytic activity when acetic acid was introduced, leading to a significant elevation in the catalytic wave at −1.6 V (V vs. Ag wire). The most pronounced activity was observed by adding 15 mM acetic acid, with a turnover number (TON) of 10.1. The catalyst’s durability was confirmed through controlled potential electrolysis (CPE) at −1.6 V for 2 h, displaying a steady current for the initial 20 min, followed by a gradual increase over the subsequent 2 h. A negligible amount of deposited metallic cobalt on the surface of the glassy carbon electrode through a ligand dissociation was evident during the electrocatalytic studies, as ensured by X-ray Photoelectron Spectroscopy (XPS) analysis. Further, the presence of ligand-centric reduction wave in the complex signifies the synergistic effect of the M−L cooperation and offers a plausible ECEC mechanistic route for the release of molecular hydrogen.

An oxo‐acetato‐bridged trinuclear cobalt(III) cluster‐persuaded cobalt oxide active electrocatalyst for efficient hydrogen evolution activity

This study presents the synthesis and electrocatalytic performance of the cobalt(III) complex [Co3(μ1,1,1‐O)(μ1,3‐CH3CO2)(L)3]2(DMF)3 (Cotri), featuring a double deprotonated (N,O)‐donor ligand (L2‐), where the protonated form of it (H2L) is 2,2′‐(hydrazine‐1,2‐diylidenebis(ethan‐1‐yl‐1‐ylidene))diphenol. The X‐ray structure reveals a trinuclear cobalt cluster formed with three cobalt(III) centers interlinking through oxido (μ1,1,1‐O) and acetato (μ1,3‐O2CCH3) bridges in coupling with bis‐congregator‐type chelating ligands. Cotri adopts cobalt centers of octahedral and trigonal bipyramidal coordination geometries and bears a dominant Co(2)…H(DMF) agostic interactions appraised by lattice dimethyl formamide (DMF) molecules. Further, Cotri shows promising heterogeneous electrocatalytic hydrogen evolution activity in 1 M KOH, with an overpotential of 441 mV to achieve 10 mA/cm2 current density. Tafel slope analysis suggests the Volmer–Heyrovsky step as the rate‐determining step. The number of active sites and TOF for Cotri were estimated at 4.010 × 10−8 mol and 0.2467 s−1, respectively, ensuring its excellent hydrogen generation activity. Stability assessments through controlled potential electrolysis (CPE) and cyclic voltammetry (CV) for multiple cycles addressed the transformation of Cotri to Co2O3 nanoparticles, which turned out to be a more active Co2O3 electrocatalyst. The morphology and particle size of the in situ developed Co2O3 active catalyst under the electrochemical conditions attributes to the superior hydrogen evolution activity.

Electrodeposition behaviour of samarium in 1,3-dimethyl-2-imidazolidone solvent

Abstract The present study investigates the electrochemistry spectroscopy of Sm(III), and electrodeposition of samarium metal in neutral ligand-based ionic liquid (solvate ionic liquid). Mixture consisted of a samarium precursor (either samarium triflate or samarium nitrate hexahydrate) in the solvate ionic liquid, 1.3-dimethyl-2-imidazolidone (DMI). FT-IR analysis of Sm(III)-DMI electrolytes indicates that Sm3+ ion coordinates with DMI through carbonyl group (C=O); the band splits into two with emergence of new peak at 1630 cm−1 and 1649 cm−1 for the triflate and nitrate solutions, respectively. Raman spectroscopy also confirms the solvation of Sm(III) with DMI through oxygen atom of the carbonyl group. Voltametric behaviour of Sm(III) ion indicates two-step reduction mechanism via Sm(III)/Sm(II) at ca. −2.0 V and Sm(II)/Sm(0) at ca. −3.0 V vs. Ag/Ag+ for both samarium(III)-containing electrolytes. Diffusion coefficient value of Sm(III) was determined to be 2.185 × 10−6 cm2/s and 2.418 × 10−8 cm2/s for triflate and nitrate electrolytes, respectively. Electrodeposition of samarium was achieved through constant potential electrolysis using copper substrate as the working electrode which yielded compact deposits from triflate-DMI and non-uniform granular deposit from nitrate-DMI electrolyte. Ex situ X-ray photoelectron spectroscopy analysis of the as-deposited samples revealed the presence of metallic Sm (1081 eV) co-existing with its oxide form (1083 eV).

Design and synthesis of heteroleptic Ni(II) dipyrrin complexes for electrochemical proton reduction reactions: Cyclic voltammetric and theoretical studies

The effect of nuclearity on electrochemical hydrogen generation using new heteroleptic Ni(II) complexes containing redox-active dipyrrin and dithiocarbamate ligands has been described. Complexes 1–2 have been meticulously characterized by spectroscopic studies (ESI-MS, IR, 1H, 13C NMR, UV–vis) and their structures unambiguously confirmed by X-ray single crystal analyses. Electrocatalytic properties of the complexes toward hydrogen evolution reaction have been investigated by cyclic voltammetric studies in an organic medium in the presence of acetic acid as a weak proton source. Notably, complexes 1 and 2 produce H2 via doubly reduced Ni(II) species i.e. Ni(0) in the presence of acetic acid. Further, these complexes exhibited significant electrocatalytic activity (TOF: 264 (1) and 650 s−1 (2). Controlled potential electrolysis established a minimum Faradaic efficiency of 92 (1) and 96 % (2). Complex 2 exhibited higher turnover frequency relative to 1, while 1 showed lower overpotential (0.35 V) in comparison to 2 (0.45 V). The stability of the complexes and the amount of produced H2 has been investigated by bulk electrolysis study. A tentative mechanism (ECEC; E, electrons and C, chemical steps) and involved intermediate species for the proton reduction reaction for 1 has been established by theoretical studies.

Facile Preparation of Stable NiII‐ and CoII‐tetraaminophthalocyanine Electropolymers for Highly Efficient Heterogeneous Carbon Dioxide Reduction

This study focused on preparation of stable polymer films of NiII‐ and CoII‐tetraaminophthalocyanines, p‐NiTAPc and p‐CoTAPc, respectively, for highly efficient heterogeneous electrochemical carbon dioxide (CO2) reduction in a flow electrolysis cell. Major development represented in this work was fabrication of p‐NiTAPc and p‐CoTAPc films via electropolymerization of their corresponding monomers on carbon‐based substrates without using binder or conducting additive materials to obtain efficient gas diffusion electrodes (GDEs) for scalable, productive and selective CO2‐to‐CO conversion. The target polymers were characterized by UV‐visible spectrophotometry, attenuated total reflection‐Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy and cyclic voltammetry. According to controlled potential electrolysis and gas chromatography, p‐NiTAPc‐catalyzed CO2 reduction at –0.99V vs. reversible hydrogen electrode (RHE) gave 953 mL of CO in a period of 16 hours with current density and Faradaic efficiency (FE) of 109±1 mA·cm‐2 and 99±2%, respectively. A p‐CoTAPc‐modified GDE exhibited superior catalytic performance to the case of p‐NiTAPc in terms of catalyst stability and CO productivity by performing the continuous CO2 reduction at the potential of –1.10 V vs. RHE for up to 41 hours and affording almost 3 times higher amount of CO with the current density of 161±5 mA/cm2 and 95±2% FE.

Cation-driven self-assembly of core–shell covalent organic frameworks@Ti3CN MXene nanospheres for high-performance aqueous zinc-ion hybrid supercapacitors

Rechargeable aqueous Zn-ion hybrid supercapacitors (ZISCs) with the superiorities of high theoretical capacity, low redox potential and aqueous electrolytes with superior ionic conductivity (∼1 S cm−1) are promising energy storage systems. However, a primary concern persists due to the absence of cathode materials with both high energy densities and satisfactory cycling stability for robust ZISCs. In this study, we design a spherical core–shell covalent organic frameworks@Ti3CN MXene (CM-P) cathode via a cation-driven electrostatic self-assembly strategy. The CM-P with the constructed heterostructures shows both well-organized pore channels and excellent intrinsic conductivity, facilitating fast accessibility to intrinsic redox-active sites (such as C = O and N), and promoting effective ion diffusion characterized by low energy barriers. Consequently, the CM-P cathodes demonstrate excellent electrochemical performance, featuring an ultrahigh specific capacity of 260 mAh/g at 0.1 A, a high-rate capability with 68 % retention at 1 A/g, and long-term cycling stability. First-principle calculations elucidate that the enhanced charge-storage mechanism relies on the heterostructures of CM-P, accelerating ion adsorption/diffusion and electron transfer. Furthermore, the assembled CM-P//Zn ZISCs devices show a high energy density of 217.1 Wh kg−1 along with power density of 22.3 kW kg−1. This work provides an innovative approach to design COFs-based heterostructures for advanced ZISCs.

Mechanistic Insights into Electrocatalytic Hydrogen Evolution by an Exceptionally Stable Cobalt Complex.

Co(aPPy) is one of the most stable and active molecular first-row transition-metal catalysts for proton reduction reported to date. Understanding the origin of its high performance via mechanistic studies could aid in developing even better catalysts. In this work, the catalytic mechanism of Co(aPPy) was electrochemically probed, in both organic solvents and water. We found that different mechanisms can occur depending on the solvent and the acidity of the medium. In organic solvent with a strong acid as the proton source, catalysis initiates directly after a single-electron reduction of CoII to CoI, whereas in the presence of a weaker acid, the cobalt center needs to be reduced twice before catalysis occurs. In the aqueous phase, we found drastically different electrochemical behavior, where the Co(aPPy) complex was found to be a precatalyst to a different electrocatalytic species. We propose that in this active catalyst, the pyridine ring has dissociated and acts as a proton relay at pH ≤ 5, which opens up a fast protonation pathway of the CoI intermediate and results in a high catalytic activity. Furthermore, we determined with constant potential bulk electrolysis that the catalyst is most stable at pH 3. The catalyst thus functions optimally at low pH in an aqueous environment, where the pyridine acts as a proton shuttle and where the high acidity also prevents catalyst deactivation.

Dinuclear Copper Complex for High‐Rate Hydrogen Evolution Under Neutral Aqueous Conditions

AbstractThe development of an efficient and stable electrocatalyst for the hydrogen evolution reaction (HER), based on earth‐abundant components, represents a crucial step toward cost‐effective and environmentally friendly hydrogen production. This study presents the utilization of a dinuclear copper catalyst, denoted as [Cu‐Gly‐SB] (Complex 1), for HER under both aqueous and non‐aqueous conditions. In non‐aqueous settings, the catalyst achieves excellent HER performance, requiring only a 270 mV overpotential when acetic acid is used as the proton donor. Notably, in fully aqueous conditions, complex 1 attains a remarkable current density of 18.8 mA ⋅ cm−2 at −0.7 V vs. RHE in cyclic voltammetry. The kobs value of ≈2.7×104 s−1 in aqueous solution at pH 7.0 further underlines the superior catalytic performance of 1, outperforming most non‐noble‐metal molecular catalysts functioning in fully aqueous solutions. The robust stability of 1 is demonstrated through controlled potential electrolysis (CPE) over a span of 48 hours, achieving an impressive catalytic current of 11.0 mA ⋅ cm−2 at −0.39 V. Moreover, the catalytic current gradually increases with higher reduction potentials, reaching a substantial 100 mA ⋅ cm−2 at an overpotential of 590 mV during CPE >48 hours. Thorough characterizations further confirm the molecular nature of the catalyst.

Comparative analysis of Benchmark and Aeon Blue Technologies for sustainable eFuel production: Integrating Direct Air Capture and Green Hydrogen approaches

Renewable Fuels of Non-Biological Origin (RFNBOs, a.ka. “eFuels”) are drop-in replacements for fossil fuels in the “hard-to-abate” sectors, and utilise existing distribution and storage infrastructure, but suffer from low synthetic efficiency. In particular, the low efficiency and high energy consumption of hydrogen synthesis by freshwater electrolysis remains a problem to be addressed. In the current study, we explore the potential of saltwater electrolysis (chloralkali) for the synthesis of eFuels generally, and specifically eMethanol. The study explores the use of chlorinated water in carbonate-loop pH-swing “cold capture” of carbon dioxide, and the resulting synergetic integration of the chloralkali process in eFuel syntheses. Doing so eliminates the high energy consumption of the calciner and the slaker of the benchmarked carbonate-loop thermal-swing method. It is replaced with a spontaneous chemical process in which chlorine is neutralized in the presence of carbonates. This allows the simultaneous solution of “The Chlorine Problem” of saltwater electrolysis, and a lower overall energy consumption of direct air capture when combined with green hydrogen synthesis. The only limitation on the comparison is that a large amount of carbon dioxide is over-captured when using chloralkali. That is, the ratio of hydrogen generated to carbon dioxide captured is fixed by the stoichiometry of chloralkali and not that of the eFuel. This results in an excess of carbon captured and thus a carbon-negative eFuel. We examine one configuration of secondary revenue and use it to inform the marginal cost of CO2 capture. In the system proposed by Aeon Blue Technologies (ABT), carbon dioxide is absorbed into caustic according to the standard method. Hydrogen gas is produced in a standard chloralkali electrolyzer, along with caustic for the contactor, and chlorine. Water oxidation by chlorine gives the strong acid, hydrochloric acid, and the weak acid, hypochlorous acid, which react directly with wet carbonate to release CO2. H2 and CO2 react in a methanol reactor to produce eFuel. H2 is the limiting reagent for eFuel synthesis, giving an excess of cold captured CO2. Thus, the current study underscores significant advancements in renewable fuel synthesis, particularly eMethanol, and evaluates the carbon capture and energy efficiency of a novel method. The simulation indicates that the marginal energy cost for a tonne of CO2 is ∼ 184kWh. This gives ∼ 76 % theoretical carbon capture efficiency and an overall process efficiency of 79.5 % (approximately a threefold improvement over the benchmark). The authors are unaware of a comparable method. The overall system yields a tonne of carbon-neutral e-methanol (eMeOH) while capturing an additional 3 tonnes of carbon dioxide, which means the modelled process captures over 300 % more carbon dioxide than is released upon combustion of the eFuel. In summary, this research contributes valuable insights into carbon-negative eFuel production, representing a significant scientific step in sustainable fuel production.