Alkaline Solution Research Articles

Modeling bicarbonate formation in an alkaline solution with multi-level quantum mechanics/molecular dynamics simulations

Understanding carbonate speciation and how it may be modulated is essential for the advancement of carbon dioxide (CO2) capture and storage technologies, which often rely on the transformation of CO2 into carbonate, e.g. via the formation of carbonate minerals. To date, few atomic-level, quantum-mechanics-based simulations have been carried out to characterize how carbonic acid (H2CO3) and bicarbonate ( HCO 3 − ) form in aqueous solution, and how pH affects this process. Recently, Martirez and Carter utilized rare-event sampling density functional theory molecular dynamics simulations in combination with multi-level embedded correlated wavefunction theory, thus accounting for both solvent dynamics and electron correlation accurately, to elucidate the mechanism of H2CO3 formation in neutral solution (J. Am. Chem. Soc., 145, 12561, 2023). Here, we perform a complementary simulation using the same method to map out the energetics of HCO 3 − formation from dissolved CO2 in basic solution. We find that, as in H2CO3 formation, including water dynamics is important to obtain an accurate prediction of the energetics for the aforementioned reaction. Furthermore, only with MD did we identify the correct pathway for the reaction, in which water – not hydroxide – acts as the initial nucleophile and only at the transition state does it lose a proton.

Atomically dispersed Au single sites and nanoengineered structural defects enable a high electrocatalytic activity and durability for hydrogen evolution reaction and overall urea electrolysis

The development of exceptionally active and stable trifunctional electrocatalysts is essential to facilitate industrial applications of proton exchange membrane electrolyzers. Rare earth catalysts have a wide range of applications in alkaline solution oxidation, but limitations in their stability and activity prevent their further application. In this paper, Au doped CeO2 coated porous Aux/CeO2 (x = 1,2,3) was designed as a three-function electrocatalyst with excellent performance and stability. At 1 M KOH conditions, both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) reactions exhibit excess potentials of 159.6 and 320.8 mV at a current density of 10 mA cm-2. In addition, when incorporated into an Au2/CeO2 (0.05 mmol, HAuCl4·4H2O) microparticles, the catalyst exhibits the potential of 1.42 V(10 mA cm-2) containing 0.33 M urea in 1 M KOH. Remarkably, for hydrogen production driven by urea electrolysis, Au2/CeO2 demonstrated exceptional performance by requiring only a voltage input of 1.63 V. The reducing agent that forms the Au/CeO2 heterojunction modulates the electronic structure of the Au active site and optimizes the adsorption of the intermediate. In addition, the interaction of the Au monolayer with the CeO2 nanosphere effectively prevents excessive oxidation and dissolution of Au, and the porous hollow structure provides additional exposed active sites and facilitates mass transfer.

Optimization of Hydrochemical Leaching Process of Kaolinite Fraction of Bauxite with Response Surface Methodology

A technology for the hydrochemical processing of the kaolinite fraction of bauxite has been developed, and it involves preliminary chemical activation in a sodium bicarbonate solution and alkaline leaching in a recycled high-modulus solution with the addition of an active form of calcium oxide. Chemical activation allows for the transformation of the difficult-to-explore kaolinite phase to form easily soluble phases of dawsonite, sodium hydroaluminosilicate and bemite. An active, finely dispersed form of calcium oxide was obtained as a result of CaO quenching in Na2SO4 solution at elevated temperature and pressure. Using a central composite design (CCD) via response surface methodology (RSM), the technological leaching mode was achieved. The influence on the leaching process was studied by adjusting the CaO/SiO2 ratio, temperature, alkaline solution concentration and duration. It was found that the determining factors are the concentration of the leaching solution and the temperature. At a stable CaO/SiO2 ratio, a combination of these two factors determines the duration of the process to achieve the predicted degree of recovery. The results of experiments carried out using the developed model of the leaching process confirmed the validity of the calculated indicators, with an error of 2.01%. In an optimal technological mode at a Na2O leaching solution concentration of 260 g/L, a temperature of 260 °C, a CaO/SiO2 ratio of 1.5 and a leaching time of 5 h, the extraction of Al2O3 into the solution was 89.7%, which is close to the value of 87.9% predicted by the model.

Reactivity and Durability of Covalent Organic Frameworks Derived Co‐Based Hybrid Bifunctional Electrocatalysts for Zinc‐Air Batteries

AbstractDeveloping bifunctional non‐precious metal electrocatalysts of superior reactivity and durability is essential. Herein, we report a class of phthalocyanine‐based covalent organic frameworks as self‐sacrificial precursors derived Co‐based hybrid electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The fabricated Co‐COFs/CNT‐700 catalysts displayed highly efficient ORR properties with a half‐potential of 0.83 V, while its half‐wave potential in alkaline solution at a current density of 10 mA cm−2 is 1.70 V in the OER test, reflecting exceptional OER activity. Moreover, zinc‐air batteries assembled with Co‐COFs/CNT‐700 catalysts exhibit a marginally higher power density (114 mW cm2) than traditional Pt/C−IrO2 batteries in an air atmosphere, along with an enhanced cycling stability (5.1 % potential loss after 65 h). This work may pave a facile and efficient approach for fabricating electrocatalytic materials with controllably introduced metals and heteroatoms.

Modulating the Bader Charge Transfer in Single p-Block Atoms Doped Pd Metallene for Enhanced Oxygen Reduction Electrocatalysis.

Metallene is considered as an emerging family of electrocatalysts due to its atomically layered structure and unique surface stress. Here we propose a strategy to modulate the Bader charge transfer (BCT) between Pd surface and oxygenated intermediates via p-d electronic interaction by introducing single-atom p-block metal (M=In, Sn, Pb, Bi) into Pd metallene nanosheets towards efficient oxygen reduction reaction (ORR). X-ray absorption and photoelectron spectroscopy suggests that doping p-block metals could facilitate electron transfer to Pd sites and thus downshift the d-band center of Pd and weaken the adsorption energy of O intermediates. Among them, the developed Bi-Pd metallene shows extraordinarily high ORR mass activity of 11.34 A mgPd -1 and 0.86 A mgPd -1 at 0.9 V and 0.95 V in alkaline solution, respectively, representing the best Pd-based ORR electrocatalysts ever reported. In the cathode of a Zinc-air battery, Bi-Pd metallene could achieve an open-circuit voltage of 1.546 V and keep stable for 760 h at 10 mA cm-2. Theoretical calculations suggest that the BCT between Pd surface and *OO intermediates greatly affects the bond length between them (dPd-*OO) and Bi doping could appropriately reduce the amount of BCT and stretch the dPd-*OO, thus enhancing the ORR activity.

The denitrification characteristics of Na2S2O8 solution in a falling film reactor

ABSTRACT Wet scrubbing technology is an effective emission control technology for marine diesel engines. Nitric oxide (NO) is one of the main component of ship emissions, the sodium persulfate (Na2S2O8) can facilitate the NO mass transfer process to a rapid reaction. Falling film reactors are widely used in rapid gas–liquid reactions, however, the reaction characteristics of denitrification using Na2S2O8 solution in a falling film reactor are not clear, which were investigated in this paper. The factors of NO mass transfer flux were tested with the liquid–gas ratio of 15 L/m3. The effects of solution properties and temperatures on the reaction driving force were studied by calculating the chemical reaction equilibrium constants and Gibbs free energy changes. The results showed that the NO mass transfer flux increased with the increase of temperature, Na2S2O8 concentration, O2 concentration and NO concentration. NO mass transfer flux increased by 41.00% and then decreased by 2.12% as the pH value increased from 7 to 10 and then rising to 12. The Gibbs free energy changes of alkaline solutions were 114.22%−130.99% lower than those of acidic solution at 303–343 K, and the chemical reaction equilibrium constants were higher. Na2S2O8/seawater system has great application potential in marine exhaust gas purification.

Impact of Different Red Blood Cell Storage Solutions and Conditions on Cell Function and Viability: A Systematic Review.

Red blood cell (RBC) storage solutions have evolved significantly over the past decades to optimize the preservation of cell viability and functionality during hypothermic storage. This comprehensive review provides an in-depth analysis of the effects of various storage solutions and conditions on critical RBC parameters during refrigerated preservation. A wide range of solutions, from basic formulations such as phosphate-buffered saline (PBS), to advanced additive solutions (ASs), like AS-7 and phosphate, adenine, glucose, guanosine, saline, and mannitol (PAGGSM), are systematically compared in terms of their ability to maintain key indicators of RBC integrity, including adenosine triphosphate (ATP) levels, morphology, and hemolysis. Optimal RBC storage requires a delicate balance of pH buffering, metabolic support, oxidative damage prevention, and osmotic regulation. While the latest alkaline solutions enable up to 8 weeks of storage, some degree of metabolic and morphological deterioration remains inevitable. The impacts of critical storage conditions, such as the holding temperature, oxygenation, anticoagulants, irradiation, and processing methods, on the accumulation of storage lesions are also thoroughly investigated. Personalized RBC storage solutions, tailored to individual donor characteristics, represent a promising avenue for minimizing storage lesions and enhancing transfusion outcomes. Further research integrating omics profiling with customized preservation media is necessary to maximize post-transfusion RBC survival and functions. The continued optimization of RBC storage practices will not only enhance transfusion efficacy but also enable blood banking to better meet evolving clinical needs.

Characterization and Enhanced Production of Fungal Melanin from Aspergillus Species Isolated from Soil

This study aimed to isolate and identify fungi from soil samples, focusing on their ability to produce melanin. Eleven different genera of fungi were isolated and identified using lactophenol cotton blue staining and microscopic examination, referencing H.L. Barnett and Barry B. Hunter. Among these, only Aspergillus was found to produce melanin. Optimal melanin production conditions were determined to be a 1.5% tyrosine supplement in the growth medium, under shaking conditions (120 rpm) and dark incubation for three weeks, resulting in a yield of 21.08 mg/100 ml. Physiochemical characterization revealed that the extracted melanin was insoluble in organic solvents but soluble in alkaline solutions (NaOH, KOH), and partially soluble in DMSO. Spectrometric analysis using UV-Visible spectroscopy showed characteristic absorption peaks. FTIR indicated functional groups and Scanning Electron Microscopy (SEM) images displayed a granular and heterogeneous surface topology. The study also assessed the effects of different carbon and nitrogen sources, and trace elements on melanin production. Maltose and sucrose were the most effective carbon sources, while peptone was the most effective nitrogen source. Among trace elements, calcium significantly enhanced melanin yield, while copper and zinc had moderate effects. These findings provide valuable insights into optimizing fungal melanin production and its potential industrial applications. The study highlights the sustainable and scalable production of melanin from Aspergillus, contributing to the broader understanding of fungal metabolites and their commercial exploitation. Future research should focus on genetic and metabolic pathways to further enhance melanin biosynthesis and explore its diverse applications.

Atomically dispersed Fe–N4 sites activated 3D-on-2D derived porous carbon structure toward superior oxygen reduction reaction

The oxygen reduction reaction (ORR) is a crucial step in the energy transformation devices, which requires the fabrication of a cost-effective and energy-efficient Fe single-atom catalyst (SAC) to substitute platinum. However, achieving a controllable synthesis of Fe SAC is a formidable challenge. In this study, a Fe SAC with a novel 3D-on-2D architecture was fabricated by coating 3D metal-organic frameworks (MOFs) over the surface of 2D reduced graphene oxide (rGO). In-situ combining MOF and rGO in a composite structure by adjusting their weight proportion is a key to preparing an active 3D-on-2D structured catalyst with FeN4 active sites. Thanks to the favorable conductivity of the 2D rGO-derived carbon structure and the 3D MOF structure exposing an enhanced density of FeN4 sites, FeNC@rGO-2 demonstrates exceptional ORR activity. It performs more effectively than commercial Pt/C, exhibiting excellent half-wave potentials of 0.887, 0.705, and 0.741 V in alkaline, neutral, and acidic solutions respectively. Impressively, FeNC@rGO-2 exhibits excellent stability and methanol tolerance. When FeNC@rGO-2 is assembled as cathode catalyst in Zinc-air batteries (ZAB) and microbial fuel cells (MFC), FeNC@rGO-2-ZAB reveals outstanding power density (393 mW cm−2) and good charge/discharge cycling stability. Amazingly, FeNC@rGO-2-MFC also shows superior power density (2810 ± 19 mW m−2) and efficiency of electron recovery. This study reveals that FeNC@rGO-2 has extremely high application value in energy conversion devices oriented for alkaline and neutral electrolytes.

Synergistic effect of iron tailings, steel slag and red mud cementitious materials on mechanical and microstructure properties

Utilizing industrial solid waste for cementitious materials addresses ecological environmental pollution, and contributes significantly to reducing carbon emission, thus fostering sustainable development. The cementitious materials were prepared using three types of solid waste: red mud (RM), iron tailings (IR) and steel slag (SS) in this study. The impact of the synergistic interaction between RM-IR-SS on the mechanical properties was investigated. Additionally, the hydration products were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetry derivative thermogravimetry (TG) and Scanning Electron Microscopy (SEM). The results showed that the optimum strength reached 11.83 MPa after curing 28 d with a composition of 30 % RM, 40 % IR, 30 % SS a solid-liquid ratio of 0.35 and an alkaline activator module of 1.30. RM was found to be rich in OH−, which formed an alkaline solution upon contact with water. This solution, in interaction with alkaline activators, effectively dissolved large amount of Si and Al substances from RM, IR and SS. The dissolved Na+, Ca2+, [Al(OH)6]3-, [H3SiO4]-, [H3AlO4]2-, and OH− reacted to generate ettringite, C–S–H, and C(N)-A-S-H gels. The diffusion of these gel and ettringite, coupled with the reduction of porosity, formed a dense matrix structure, which improved the mechanical properties. The research establishes a solid foundation for the optimal utilization of alkali, calcareous, and silica-aluminum solid waste, further contributing to a more sustainable industrial ecosystem through their synergistic utilization as building materials.

Electrostatic Surface Charging by Water Dewetting.

Water dewetting generates static electricity. We reviewed historical experiments of this phenomenon, and we studied the charging of polymer slides and metal electrode supported polymer films withdrawn vertically from a pool of aqueous solutions. For pure water, charging was negative and surface charge densities increased with the speed of dewetting, which we explain by the thermally activated entrainment of nanometer-sized water droplets or clusters charged by unbalanced adsorbed electric double-layer ions. Surface charge densities increased for reduced polymer film thickness following a power law, which we explain by reduced discharge of the entrained water volumes. At low salinity c ≲ 10 μM, charging was proportional to electrokinetic interfacial charge densities: the negative charging was increased for alkaline solutions and for most salts at μM concentrations and the charge polarity was inversed to positive for a cationic surfactant, a salt with a highly positively charged cation, and for a strong acid at approximately pH 4. Charging was reduced again for c ≳ 100 μM, especially at high dewetting speeds and for chaotropic ions, which we explain by the entrainment of larger and more discharged droplets. We determined adsorption energies of the charged water clusters on the dewetted surface from thermally stimulated discharge of the charged polymer slides and we show that the surface charge distribution, imaged by charged toner powders and measured microscopically by Kelvin probe force microscopy, is a record of the dewetting process that provides spatial and kinetic information about the three-phase contact line motion.

PH-Universal Electrocatalytic CO2 Reduction with Ampere-Level Current Density on Doping-Engineered Bismuth Sulfide.

The practical application of the electrocatalytic CO2 reduction reaction (CO2RR) to form formic acid fuel is hindered by the limited activation of CO2 molecules and the lack of universal feasibility across different pH levels. Herein, we report a doping-engineered bismuth sulfide pre-catalyst (BiS-1) that S is partially retained after electrochemical reconstruction into metallic Bi for CO2RR to formate/formic acid with ultrahigh performance across a wide pH range. The best BiS-1 maintains a Faraday efficiency (FE) of ~95 % at 2000 mA cm-2 in a flow cell under neutral and alkaline solutions. Furthermore, the BiS-1 catalyst shows unprecedentedly high FE (~95 %) with current densities from 100 to 1300 mA cm-2 under acidic solutions. Notably, the current density can reach 700 mA cm-2 while maintaining a FE of above 90 % in a membrane electrode assembly electrolyzer and operate stably for 150 h at 200 mA cm-2. In situ spectra and density functional theory calculations reveals that the S doping modulates the electronic structure of Bi and effectively promotes the formation of the HCOO* intermediate for formate/formic acid generation. This work develops the efficient and stable electrocatalysts for sustainable formate/formic acid production.

Tailoring the composition of a non-noble, Cubic Shaped MnSn(OH)6 Bi-functional electrocatalysts for methanol and urea oxidation reactions in alkaline solutions

A systematic study of the effect of Sn-precursor concentration on the composition of (MnSn(OH)6) is carried out, and the samples' structural, morphological, and electrochemical variations are investigated. Four different SnCl2·5H2O precursor concentrations (5, 10, 20, and 40 mM) are varied to synthesize MnSn(OH)6 electrocatalysts, denoted as MS-1, MS-2, MS-3, and MS-4, respectively, using a hydrothermal method. All four samples' crystal structure and chemical states are identified using X-ray diffraction analysis and X-ray photoelectron microscopy. Morphological studies are carried out using scanning electron and transmission electron microscopy studies. The electrocatalytic performance and the stability of the synthesized samples are evaluated using cyclic voltammetry and chronoamperometry. Among the samples, MS-3, which has an optimized ratio of Mn/Sn, displayed the highest current density values of 80.3 mA g−1 and 84.7 mA g−1 at a higher potential of 0.7 V for the urea oxidation reaction in the presence of 0.33 M urea + 1.0 M KOH and for the methanol oxidation reaction in the presence of 0.5 M methanol + 1.0 M KOH, respectively. This intrinsic activity of MS-3 samples is due to its more significant electrochemically active surface area value of 208 mF cm−2, primarily because of the dominance of Mn3+ on the surface. Furthermore, MS-3 displayed reduced overpotential, as evidenced by the onset potential of 1.45 (V vs RHE) @ 10 mA cm−2, indicating enhanced electrocatalytic performance. These findings highlight the importance of tuning the Mn/Sn metal ratio to design and develop cost-effective non-precious electrocatalysts for urea and methanol oxidation reactions.

PH‐Universal Electrocatalytic CO2 Reduction with Ampere‐Level Current Density on Doping‐Engineered Bismuth Sulfide

AbstractThe practical application of the electrocatalytic CO2 reduction reaction (CO2RR) to form formic acid fuel is hindered by the limited activation of CO2 molecules and the lack of universal feasibility across different pH levels. Herein, we report a doping‐engineered bismuth sulfide pre‐catalyst (BiS‐1) that S is partially retained after electrochemical reconstruction into metallic Bi for CO2RR to formate/formic acid with ultrahigh performance across a wide pH range. The best BiS‐1 maintains a Faraday efficiency (FE) of ~95 % at 2000 mA cm−2 in a flow cell under neutral and alkaline solutions. Furthermore, the BiS‐1 catalyst shows unprecedentedly high FE (~95 %) with current densities from 100 to 1300 mA cm−2 under acidic solutions. Notably, the current density can reach 700 mA cm−2 while maintaining a FE of above 90 % in a membrane electrode assembly electrolyzer and operate stably for 150 h at 200 mA cm−2. In situ spectra and density functional theory calculations reveals that the S doping modulates the electronic structure of Bi and effectively promotes the formation of the HCOO* intermediate for formate/formic acid generation. This work develops the efficient and stable electrocatalysts for sustainable formate/formic acid production.

The flexural mechanical properties and mesoscopic mechanisms of fracture failure of HPC with ASR inhibition measures under prolonged alkaline solution immersion

The flexural mechanical properties and mesoscopic mechanisms of fracture failure of HPC with ASR inhibition measures under prolonged alkaline solution immersion

Facile Lignin Extraction and Application as Natural UV Blockers in Cosmetic Formulations

Natural compounds are becoming increasingly popular in the fields of pharmaceuticals and cosmetics. One such compound is lignin, a plant-derived aromatic polymer that serves as a natural anti-ultraviolet agent. Conventional methods for extracting lignin from plant materials typically involve performing procedures in harsh environments, such as dissolving it in highly alkaline solutions or subjecting it to treatment in acidic conditions. In this study, lignin was extracted from coconut husk under milder conditions, using neutral solvents and ultrasonic treatment, which allowed us to obtain lignin with significantly improved properties. The developed method facilitated the creation of light-colored lignin, which was employed as a natural ingredient in sunblock cream. Furthermore, for the sake of comparison, lignin was extracted under more rigorous conditions using the traditional method. The research findings confirm that the light-colored lignin sample exhibits a higher level of UV absorption. Furthermore, light-colored lignin demonstrates a synergistic effect when combined with commercial moisturizing creams and sunscreens, leading to a significant enhancement in their SPF performance against both UVA and direct sunlight exposure. This study highlights the potential value of incorporating lignin as a valuable natural ingredient in sunblock and cosmetic products.

In situ growth of NiMoO4-C nanocomposite and electrodeposition of multi-metal selenide to enhance oxygen evolution efficiency in alkaline solution

This study primarily centers on the fabrication of NiMoO4-C@Ni(FeMo)-Se composite electrocatalysts directly onto nickel foam substrates through a hydrothermal followed by electrodeposition technique. Through this method, the carbon submicron sphere structure, interlinked by NiMoO4 nanorods, undergoes further optimization, resulting in a more refined NiMoO4-C@Ni(FeMo)-Se core-shell structure. The NiMoO4-C@ Ni(FeMo)-Se /NF composite electrode exhibited exceptional OER catalytic activity in a 1 M KOH solution, with an overpotential of merely 228 mV at a current density of 50 mA·cm−2 and a Tafel slope of 35.9 mV·dec−1, significantly superior to that of the blank NF. Additionally, a 40-hour stability test at a current density of 50 mA·cm−2 demonstrated that the potential remained nearly constant, highlighting the exceptional OER activity and long-term stability of the synthesized catalyst. Moreover, in the overall water splitting process, the utilization of a dual-electrode NiMoO4‐C@Ni(FeMo)‐Se/NF||Pt‐C/NF electrolytic cell demands a remarkably low potential of 1.48 V to achieve a current density of 10 mA·cm−2, demonstrating exceptional electrocatalytic activity and long-term stability. Therefore, this study provides a promising route for the application of hydrogen production from alkaline aqueous solutions.

Analysis of silicon surfaces etched in aqueous HF-(HBr)–Br2-mixtures

Solutions containing hydrofluoric acid (HF), hydrobromic acid (HBr) and bromine (Br2) were investigated as novel acidic, NOx-free mixtures for wet-chemical etching of silicon wafers. HF–Br2-mixtures exhibit isotropic etching behaviour towards silicon, etch rates up to 4.0 ​μm ​min−1 were observed at room temperature, which are higher than the etch rates of commercially used alkaline solutions. HF–HBr–Br2-mixtures show anisotropic etching behaviour, texturing the surface of monocrystalline silicon wafers with random upright or random inverted pyramidal structures. Etch rates up to 2.4 ​μm ​min−1 were observed, the etch rate increases linearly with the concentration of Br2 in the etching solution. Silicon surfaces were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The light trapping efficiency of wafers etched by HF–HBr–Br2 solutions was compared to commercially available textured wafers by UV/Vis-reflectivity measurements indicating lower reflectivities for the HF–HBr–Br2-treated samples. A reaction scheme for the anisotropic dissolution of silicon in bromine-containing aqueous HF-solutions is proposed, which involves bromine as oxidizing agent.

FeNC@nitrogen doped porous carbon leaf-carbon nanotube hybrids for oxygen reduction reaction

A series of nitrogen doped porous carbon leaf-carbon nanotubes incorporated FeNx electrocatalysts (FeNC@NCL-CNT) are prepared by pyrolysis of Fe doped leaf-like Zn-zeolitic imidazolate framework (FeZn-ZIF-L) with different Fe contents. Among the catalysts, FeNC@NCL-CNT-3 exhibits the highest ORR activity in alkaline solution with onset potential (Eonset) of 0.95 V, half-wave potential (E1/2) of 0.81 V, and limiting diffusion current density of 6.14 mA cm−2. The Eonset and E1/2 of FeNC@NCL-CNT-3 are positively shifted by ca. 20 and 6 mV, respectively compared with Pt/C. The self-generated CNT caused by Fe catalysis improves the electronic conductivity and enlarges the average pore size of the catalyst from 1.77 to 8.12 nm. The highest density of pyridine-N and Fe-Nx active sites (50.7 %) and the largest electrochemically active surface area (ECSA, 1075 cm2) also contribute to its superior activity. The Tafel slope of FeNC@NCL-CNT-3 is 75.4 mV dec-1, which is close to that of Pt/C. Fe-NCL/CNT-3 shows excellent long-term stability (99.4 % retention) and superior methanol tolerance. It catalyzes ORR through 4e- path.

Effect of alkali metal cations in alkaline iron battery electrodes

Abstract Rechargeable alkaline iron batteries (e.g. Ni-Fe and Fe-air) have been extensively studied recently as viable energy storage systems for renewable energy sources. However, inherent issues such as passivation of the iron and parasitic hydrogen evolution reaction (HER) on the electrode surface limit their full capability. Multiple approaches to improving iron electrode performance have been conducted, few of which focused on electrolyte composition. While alkali metal (AM) cations on the electrolyte do not directly participate in the electrochemical reactions, their intrinsic characteristics can dictate the performance of the electrode. Investigating the interface interactions and electrical double layer (EDL) structure can provide a deeper insight into the operation of iron electrodes in an alkaline solution. In this work, we investigated the effect of alkali metal cations (Li+, Na+, K+, Cs+) in the electrolyte solution in inhibiting passivation and HER on electrodeposited iron on carbon paper (Fe/CP) electrodes. The electrochemical measurements show that the iron redox and HER activities of the electrode increased with increasing cation size in the electrolyte. The non-covalent interactions between hydrated alkali metal cations and adsorbed OH species resulted to the formation of quasi-adsorbed clusters which can block active sites on the electrode surface. Furthermore, the concentration of these clusters decreases with increasing cation size which resulted to higher EDL capacitance and ECSA values of the electrode. The results of this work provide a better understanding of the surface reactions on iron electrodes and can help in developing novel techniques for suppressing passivation and parasitic HER on rechargeable alkaline iron batteries.