A novel method to tailor the porous structure of KOH-activated biochar and its application in capacitive deionization and energy storage

This study reveals a novel method to tailor the micro- and meso-porous structures of activated biochar by exploiting the interaction between pre-carbonization drying conditions and carbonization temperature in KOH activation. Biochar samples were mixed with concentrated KOH and then dried under air or nitrogen for various periods of time (0–280 h) followed by carbonization at 475, 675 or 875 °C. It is confirmed that by manipulating drying conditions and carbonization temperatures, the KOH activated biochar can have a predominantly microporous, mesoporous or a combined (micro/meso) porous structure. The surface area, micropore and mesopore volumes tailored between: 488–2670 m² g⁻¹, 0.04–0.72 cm³ g⁻¹, and 0.05–1.70 cm³ g⁻¹, respectively. The mechanism of porosity development was investigated by FTIR analysis suggesting conversion of KOH to K₂CO₃ due to different drying conditions as a major role in tailoring the structure. The application of activated biochar with tailored porosity was investigated for Electric Double Layer adsorption of NaCl/NaOH to be employed in water treatment (capacitive deionization) or energy storage (supercapacitor) processes. The majorly microporous activated biochar (N₂-dried activated at 675 °C) showed promising capacitances between 220 and 245 F g⁻¹. Addition of mesoporous structure resulted in capacitances between 182 and 240 F g⁻¹ with significantly reduced electrode resistance and improved capacitive behavior as evidenced by Impedance Spectroscopy and Galvanostatic Charge/Discharge tests.     

Assessing anodic microbial populations and membrane ageing in a pilot microbial electrolysis cell

First large-scale experiences of bioelectrochemical systems (BES) are underway. However, there is still little knowledge on how the different elements that integrate a BES behave in near real-life conditions. This paper aims at assessing the impact of long-term operation on the cation exchange membrane and on the anodic biofilm of two 16 L Microbial Electrolysis Cells (MEC) designed for hydrogen production and ammonia recovery from pig slurry. Membrane deterioration was examined by physical, chemical and microscopy techniques at different locations, revealing a strong attachment of microorganisms and a significant decay in membrane properties such as ion exchange capacity and thermal stability. Anode microbial communities did not show a dramatic shift in the eubacteria composition at different sampling areas, although the relative abundance of some bacterial groups showed a clear vertical stratification. After 100 days of continuous operation, MEC performance did not declined significantly maintaining ammonium transport rates and H₂ production rates of 15.3 gN d⁻¹ m⁻² and 0.2 LH₂·L⁻¹_reactor·d⁻¹ respectively.     

Biochar and plant growth promoting rhizobacteria effects on switchgrass (Panicum virgatum cv. Cave-in-Rock) for biomass production in southern Québec depend on soil type and location

Switchgrass (Panicum virgatum L.) is a fast growing native C₄ perennial and a lignocellulosic biomass crop for North America. In combination with biochar, an active plant growth promoting rhizobacterial (PGPR) community can contribute to the long-term sequestration of carbon in soil, fix nitrogen, and enhance the availability of other nutrients to plants. Biochar and PGPR have the potential to improve grass biomass production, but they have not been tested together under high-latitude temperate zone field conditions. Therefore, the objective of this three-year field study was to determine whether there were effects on biomass yield and yield components of switchgrass (cv. Cave-in-Rock) due to a rhizobacterium that was able to mobilize soil phosphorus (Pseudomonas rhodesiae), a bacterial consortium that was able to supply nitrogen (Paenibacillus polymyxa, Rahnella sp., and Serrati sp.), and pine wood chip biochar applied as a soil amendment at 20 Mg ha⁻¹. The incorporation of biochar, or inoculation with the N-fixing consortium, and the combined inoculation of the experimental bacteria had positive effects on switchgrass height. At a loam soil site in Sainte-Anne-de-Bellevue, Québec, when nitrogen fertilizer was not applied, the addition of biochar had a positive effect on stand count (tillers m⁻¹ row). On the sandy soil in Sainte-Anne-de-Bellevue, when biochar was applied with 100 kg N ha⁻¹, biomass yield increased over the control but did not provide additional benefits over plots receiving only 50 kg N ha⁻¹. It remains unclear whether or not the increased C sequestration of this management system justifies increased N fertilizer usage.     

Effect of synthesis methods on magnetic Kans grass biochar for enhanced As(III,V) adsorption from aqueous solutions

Magnetic biochar is increasingly known as a multi-functional material and the appropriate synthesis method further increase its efficient applications. In this study, the effects of synthesis methods on the fabrication of Kans grass straw/biochar (KGS/KGB) with Fe³⁺/Fe²⁺ by chemical co-precipitation and subsequently pyrolyzing at 500 °C for 2 and 4 h were studied in details, and compared their As(III, V) adsorption potentials under different operating conditions. Magnetic biochars (MKGB3 and MKGB4) prepared from KGS revealed of superior Fe₃O₄ loading, higher As(III, V) adsorption efficiency and saturation magnetization (45.7 Am² kg⁻¹) than that of KGB (MKGB1 and MKGB2). Moreover, Thermogravimetric analysis (TGA) demonstrated three stages of decomposition and the MKGB3 and MKGB4 generated higher residual mass (>60%) at stage 3 (1000 °C) due to greater Fe₃O₄ composite in biochar matrix and turned to be thermally more stable. As(III) and As(V) adsorption equilibrium data well fitted in Langmuir model and followed the order: MKGB4 > MKGB3 > MKGB2 > MKGB1. The maximum As(III) and As(V) adsorption capacities were about 2.0 mg g⁻¹ and 3.1 mg g⁻¹, respectively. The data best fitted in pseudo-second-order (R² > 0.99) rather than pseudo-first-order kinetics model indicating of more complex mechanism. The adsorption of As(III) and As(V) was found to decrease with increasing in ionic strength of competing ions and PO₄³⁻ was found to strongly inhibit arsenic adsorption. Highest desorption was achieved at pH 13.5 using NaOH. This study suggests that selective adsorbent synthesis method could be useful to prepare effective adsorbent for toxic metals immobilization.     

Hydrogen bioproduction with anaerobic bacteria consortium from brewery wastewater

Biohydrogen production is a cheap and clean way to obtain hydrogen gas. In subtropical countries such as Brazil the average temperatures of 27 °C can favor the hydrogen producing bacteria growth. A mixed culture was obtained from a subtropical sludge treating brewery wastewater and anaerobic batch reactors were fed with glucose, sucrose, fructose and xylose in low concentrations (2.0, 5.0 and 10.0 g L⁻¹) at 37 °C, initial pH 5.5 and headspace with N₂ (99%) to maintain the anaerobic conditions. The inoculum was a subtropical granulated sludge from UASB (Upflow Anaerobic Sludge Blanket) reactor treating brewery wastewater. The higher H₂ yields were obtained in reactors operated with 2 and 5 g L⁻¹ of fructose and they were 1.5 mol H₂ mol⁻¹ of fructose and 1.3 mol H₂ mol⁻¹ of sucrose, respectively. The volatile fatty acids (VFA) generated at the end of operation were, predominantly, butyric and acetic acid, indicating the favoring of the metabolic route of hydrogen generation by the consortium of anaerobic bacteria from the brewery wastewater. Biomolecular analyses revealed the predominance of hydrogen producing bacteria from Firmicutes phylum distributed in the families Streptococcaceae, Veillonellaceae and uncultured bacteria. These results confirm future applications of subtropical sludges with agroindustrial wastewaters containing low concentrations of sugars on hydrogen generation.     

Structural,electrochemical and catalytic activity of Prussian blue analogues embedded with functionalized carbon for solid state battery applications

The nanoparticles of Mn_1.5[Cr(CN)₆]∙mH₂O@Ni_1.5[Cr(CN)₆]∙nH₂O core-shell prussian blue analogues (PBA) embedded with carbon additives (PBA-C) were synthesized and characterized as electrode material for solid state battery application. The impedance spectroscopy and cyclic voltametry were used to study the electrochemical properties by adding functionalized carbon in 1:1 proportion to improve the electrical performance. The value of room temperature electrical conductivity of core-shell PBA and core-shell nanoparticles mixed with vulcan carbon (PBA-C) are found to be 1.574 × 10⁻³ and 1.92 × 10⁻³ Scm⁻¹_, respectively. Using Li₇La₃Zr₂O₁₂ (LZZO) electrolyte, single cell was fabricated with PBA-C material, and studied its charging-discharging cycles, which exhibits higher current density with stable performance for 400 cycles for time slots of 400 min. The study reveals that the PBA core-shell nanoparticles mixed with carbon (PBA-C) may be a potential candidate as an electrode material in the form of a single cell using LZZO electrolyte.     

Transport of hydrogen and deuterium in 316LN stainless steel over a wide temperature range for nuclear hydrogen and nuclear fusion applications

The permeation of hydrogen and deuterium through 316LN stainless steel (316LN SS) was investigated over a wide temperature range of 300–850 °C for nuclear hydrogen and nuclear fusion applications. We presented the first complete datasets of permeability Φ, diffusivity D, and solubility S for both hydrogen (H) and deuterium (D) in 316LN SS. Φ_H and Φ_D were 3.47 × 10⁻⁷exp(−66.6 × 10³/RT) and 2.71 × 10⁻⁷exp(−67.5 × 10³/RT) mol·m⁻¹ s⁻¹ Pa^−0.5, respectively. D_H and D_D were 15.9 × 10⁻⁷exp(−56.5 × 10³/RT) and 13.8 × 10⁻⁷exp(−56.8 × 10³/RT) m²∙s⁻¹, respectively. The estimated isotope effect ratios of Φ_H/Φ_D, D_H/D_D, and S_H/S_D were ~1.4, ~1.2, and ~1.2, respectively. The previously reported results for 316LN SS were extrapolated to the temperature range used herein and were compared with the results of this study. Although some discrepancies were observed between the results of this study and previous studies, they were within the acceptable scattering range.     

Thermodynamic and kinetic properties of calcium hydride

Calcium hydride has shown great potential as a hydrogen storage material and as a thermochemical energy storage material. To date, its high operating temperature (above 800 °C) has not only hindered its opportunity for technological application but also prevented detailed determination of its thermodynamics of hydrogen sorption. In addition, calcium metal suffers from high volatility, high corrosivity from Ca (and CaH₂), slow kinetics of hydrogen sorption, and the solubility of Ca in CaH₂. In this work, a literature review of the wide-ranging thermodynamic properties of CaH₂ is provided along with a detailed experimental investigation into the thermodynamic properties of molten and solid CaH₂. The thermodynamic values of hydrogen release from both molten and solid CaH₂ were determined as ΔH_des (molten CaH₂) = 216 ± 10 kJ mol⁻¹.H₂, ΔS_des (molten CaH₂) = 177 ± 9 J K⁻¹ mol⁻¹.H_2, which equates to a 1 bar hydrogen equilibrium temperature for molten CaH₂ of 947 ± 65 °C. Similarly, in the solid-state: ΔH_des (solid CaH₂) = 172 ± 12 kJ mol⁻¹.H₂, ΔS_des (solid CaH₂) = 144 ± 10 J K⁻¹ mol⁻¹.H₂. Moreover, the activation energy of hydrogen release from CaH₂ was also calculated using DSC analysis as E_a = 203 ± 12 kJ mol⁻¹. This study provides the first thermodynamics for the Ca–H system in over 60 years, providing more accurate data on this emerging energy storage material.     

Kinetic study of thermophilic anaerobic digestion of solid wastes from potato processing

Anaerobic treatment of solid wastes from potato processing was studied in completely stirred tank reactors (CSTR) at 55 °C. Special attention was paid to the effect of increased organic loading rate (OLR) on the biogas yield in long-term experiments. Both biogas yield and CH₄ in the biogas decreased with the increase in OLR. For OLR in the range of 0.8 gl⁻¹ d⁻¹–3.4 gl⁻¹ d⁻¹, biogas yield and CH₄ obtained were 0.85 l g⁻¹–0.65 l g⁻¹ and 58%–50%, respectively. Biogas yield y as a function of maximum biogas yield y_m, reaction rate constant k and HRT are described on the basis of a mass balance in a CSTR and a first order kinetic. The value of y_m can be obtained from curve fitting or a simple batch test and k results from plotting y/(y_m−y) against 1/OLR from long-term experiments. In the present study values for y_m and k were obtained as 0.88 l g⁻¹ and 0.089 d⁻¹, respectively. The simple model equations can apply for dimensioning completely stirred tank reactors (CSTR) digesting organic wastes from food processing industries, animal waste slurries or biogas crops.     

Characterization of a β-1,4-glucosidase from a newly isolated strain of Pholiota adiposa and its application to the hydrolysis of biomass

The highly efficient β-1,4-glucosidase (BGL)-secreting strain, Pholiota adiposa SKU0714, was isolated and identified based on its morphological features and sequence analysis of internal transcribed spacer (ITS) rDNA. P. adiposa BGL (PaBGL), which contained a carbohydrate moiety, was purified to homogeneity from P. adiposa culture supernatants by 2-step chromatography on DEAE and Sephacryl gel filtration columns. The relative molecular weight of PaBGL was 60 kDa by SDS-PAGE or 59 kDa by size exclusion chromatography, indicating that the enzyme is a monomer. The pH and temperature optima for hydrolysis were 5.0 and 65 °C, respectively. PaBGL showed the highest activity towards p-nitrophenyl-β-d-glucopyranoside (V_max = 4390 U mg protein⁻¹, K_m = 2.23 mol m⁻³) and cellobiose (V_max = 3460 U mg protein⁻¹, K_m = 5.60 mol m⁻³) ever reported. Its internal amino acid sequences showed homology with hydrolases from the glycoside hydrolase family 3 (GH3), indicating that PaBGL is a member of the GH3 family. The hydrolysis of rice straw using a commercial cellulase, Celluclast^® 1.5L, resulted in a higher saccharification yield with the addition of PaBGL than with Novozyme 188. PaBGL may be a good candidate for applications that convert biomasses to biofuels and chemicals.     

Fabrication,permeation, and corrosion stability measurements of silica membranes for HI decomposition in the thermochemical iodine–sulfur process

In this study, a corrosion-stable silica membrane was developed to be used in H₂ purification during the hydrogen iodide decomposition (2HI → H₂ + I₂), which is a new application of the silica membranes. From a practical perspective, the membrane separation length was enlarged up to 400 mm and one end of the membrane tubes was closed to avoid any thermal variation along the membrane length and sealing issues. The silica membranes consisted of a three-layer structure comprising a porous α-Al₂O₃ ceramic support, an intermediate layer, and a top silica layer. The intermediate layer was composed of γ-Al₂O₃ or silica, and the top silica layer that is H₂ selective was prepared via counter-diffusion chemical vapor deposition of a hexyltrimethoxysilane.To the best of our knowledge, this is the first report of 400-mm-long closed-end silica membranes supported on Si-formed α-Al₂O₃ tubes produced via chemical vapor deposition method. A 400-mm-long closed-end membrane using a Si-formed α-Al₂O₃ tube exhibited a higher H₂/SF₆ selectivity of 1240 but lower H₂ permeance of 1.4 × 10⁻⁷ mol Pa⁻¹ m⁻² s⁻¹ with compared with the membrane using a γ-Al₂O₃-formed α-Al₂O₃ tube (907 and 5.6 × 10⁻⁷ mol Pa⁻¹ m⁻² s⁻¹, respectively). The membrane using the Si-formed α-Al₂O₃ tube was more stable in corrosive HI gas than a membrane with a γ-Al₂O₃-formed α-Al₂O₃ tube after 300 h of stability tests. In conclusion, the developed silica membranes using the Si-formed α-Al₂O₃ tubes seem suitable for membrane reactors that produce H₂ on large scale using HI decomposition in the thermochemical iodine–sulfur process.     

Scaling up self-stratifying supercapacitive microbial fuel cell

Self-stratifying microbial fuel cells with three different electrodes sizes and volumes were operated in supercapacitive mode. As the electrodes size increased, the equivalent series resistance decreased, and the overall power was enhanced (small: ESR = 7.2 Ω and P_max = 13 mW; large: ESR = 4.2 Ω and P_max = 22 mW). Power density referred to cathode geometric surface area and displacement volume of the electrolyte in the reactors. With regards to the electrode wet surface area, the large size electrodes (L-MFC) displayed the lowest power density (460 μW cm⁻²) whilst the small and medium size electrodes (S-MFC, M-MFC) showed higher densities (668 μW cm⁻² and 633 μW cm⁻², respectively). With regard to the volumetric power densities the S-MFC, the M-MFC and the L-MFC had similar values (264 μW mL⁻¹, 265 μW mL⁻¹ and 249 μW cm⁻¹, respectively). Power density normalised in terms of carbon weight utilised for fabricating MFC cathodes-electrodes showed high output for smaller electrode size MFC (5811 μW g⁻¹-C- and 3270 μW g⁻¹-C- for the S-MFC and L-MFC, respectively) due to the fact that electrodes were optimised for MFC operations and not supercapacitive discharges. Apparent capacitance was high at lower current pulses suggesting high faradaic contribution. The electrostatic contribution detected at high current pulses was quite low. The results obtained give rise to important possibilities of performance improvements by optimising the device design and the electrode fabrication.     

Enhancement of bio-hydrogen generation by spirulina via an electrochemical photo-bioreactor (EPBR)

The biological production of hydrogen by microalgae is considered as an advantageous process. However, its yields are sometimes limited. To go beyond this limit, the improvement of the H₂ generation rate by Spirulina was studied via an electrochemical photo-bioreactor (EPBR). This EPBR led to hydrogen evolution rates of up to 27.49 and 13.37 mol of H₂.d⁻¹.m⁻³ for the anode and cathode chambers, respectively, under 0.3 V voltage and ~2.5 mA current. These results represent about a 4-fold increase compared to the H₂ production rate recorded without the application of a voltage. This increase in bio-hydrogen production is correlated with a drop in the concentration of NADPH. The Electrochemical Sequential Batch Reactor (ESRB) provided a more interesting total production rate which was 2.65 m³ m⁻³ d⁻¹, compared to the batch mode, which gave 1.2 m³ m⁻³.d⁻¹. The results show, for the first time, the boosting effect of the voltage on the metabolism of H₂ production by the Spirulina strain.     

Investigation of structural,electrical and electrochemical properties of La0.6Sr0.4Fe0.8Mn0.2O3-δ as an intermediate temperature solid oxide fuel cell cathode

La_0.6Sr_0.4Fe_0.8Mn_0.2O₃ (LSFM) compound is synthesized by sol-gel method and evaluated as a cathode material for the intermediate temperature solid oxide fuel cell (IT-SOFC). X-ray diffraction (XRD) indicates that the LSFM has a rhombohedral structure with R-3c space group symmetry. The XRD patterns reveal very small amount of impurity phase in the LSFM and Y₂O₃-stabilized ZrO₂ (YSZ) mixture powders sintered at 600, 700, 800 and 850 °C for a week. The maximum electrical conductivity of LSFM is about 35.35 S cm⁻¹ at 783 °C in the air. The oxygen chemical diffusion coefficients, D_Chem, are increased from 1.39 × 10⁻⁶ up to 1.44 × 10⁻⁵ cm² s⁻¹. Besides, the oxygen surface exchange coefficients, k_Chem, are obtained to lie between 2.9 × 10⁻³ and 1.86 × 10⁻² cm s⁻¹ in a temperature range of 600–800 °C. The area-specific resistances (ASRs) of the LSFM symmetrical cell are 7.53, 1.53, 1.13, 0.46 and 0.31 Ω cm² at 600, 650, 700, 750 and 800 °C respectively, and related activation energy, E_a, is about 1.23 eV.     

A sequential approach to uncapping of theoretical hydrogen production in a sulfate-reducing bacteria-based bio-electrochemical system

The presence of undesired methanogens with Sulfate-reducing bacteria (SRBs) is a serious challenge faced by the bioelectrochemical system (BES). In the present study, we investigate the impact of ammonia pre-treated electrodes on hydrogen production in a 600 ml anaerobic (BES) enriched with sulfate-reducing bacteria (SRBs) to inhibit the CH₄ production for achieving the theoretical H₂ production. The highest hydrogen production of 3.67 ± 0.31 M/M of glucose was recorded in the BES. The BES completely inhibited the growth of methanogens after the 7^th cycle of operation. The higher hydrogen production efficiency of BES can be justified by assuming a higher hydrogen mass transfer from the electrode surface to the biofilm. In presence of sulfate, acetate acid type of the fermentation was dominating in hydrogen production, while limitation of SO₄^2? switch over to the dominance of butyric acid type fermentative hydrogen production. Despite the sign of change in the acetate to butyric acid type metabolism, the BES system was able to uncap the theoretical hydrogen production. The notable change in vector orientation of H₂, butyric acid, and hexanoic acid inferring the significant differences in the microbial community adapted on the electrodes in the R–NH₃ and R-Cont. SEM image clearly showing ammonia-treated electrode harbour more microbial growth on the electrode surface. The ratio obtained for CH₃ and CH₂ for the R–NH₃ and R-CONT of 1.316 and 1.755 respectively by FTIR stretching vibrations showing the difference in the bacterial species adapted on the bioanodes. Cumulative hydrogen production data was computed to confirm its validity of the Gompertz model, Richard model, and Logistic model. The Richard model was found in the best-fitted models for cumulative hydrogen production.     

A non-noble V2O5 nanorods as an alternative cathode catalyst for microbial fuel cell applications

This study assessed the feasibility of vanadium pentoxide (V₂O₅) as a novel cathode catalyst material in air-cathode single chamber microbial fuel cells (SCMFCs). The V₂O₅ nanorod catalyst was synthesized using a hydrothermal method. MFCs with different cathode catalyst loadings were studied. Cyclic voltammetry (CV) was used to examine the electrochemical behavior of the catalysts in the MFCs. The V₂O₅ cathode catalyst constructed with a double loading MFC exhibited the highest maximum power density of 1073 ± 18 mW m⁻² (OCP; 691±4 mV) compared with 447 ± 12 mW m⁻² (OCP; 594 ± 5 mV) and 936 ± 15 mW m⁻² (OCP; 647±5 mV) for the single loading MFC and triple loading MFC, respectively. The power density of MFC with double loaded V₂O₅ is comparable to the traditional Pt/C cathode (2067 ± 25 mW m⁻², OCP; 821 ± 4 mV), which covers up to 55% of the performance of Pt/C. This finding highlights the potential of the V₂O₅ cathode as an inexpensive catalyst material for MFCs that may have commercial applications.     

Improvement of biohydrogen production from brewery wastewater: Evaluation of inocula,support and reactor

This work explores the production of biohydrogen from brewery wastewater using as inoculum a culture produced by natural fermentation of synthetic wastewater and Klebsiella pneumoniae isolated from the environment. Klebsiella pneumoniae showed good performance as inoculum, as evaluated using assays of between 9 and 16 cycles, with durations of 12 and 24 h, carbohydrate concentrations from 2.79 to 7.22 g L⁻¹, and applied volumetric organic loads from 2.6 to 12.6 g carbohydrate L⁻¹ day⁻¹. The best results were achieved with applied volumetric organic loads of 12.6 g carbohydrate L⁻¹ day⁻¹ and cycle length of 12 h, resulting in mean volumetric productivity of 0.88 L H₂ L⁻¹ day⁻¹, maximum molar flow of 10.80 mmol H₂ h⁻¹, and mean yield of 0.70 mol H₂ mol⁻¹ glucose consumed. The biogas H₂ content was between 18 and 42%, while the mean organic compounds removal and carbohydrate conversion efficiencies were 23 and 81%, respectively. The inoculum produced by natural fermentation was not viable.     

Design of direct solar PV driven air conditioner

Solar air conditioning system directly driven by stand-alone solar PV is studied. The air conditioning system will suffer from loss of power if the solar PV power generation is not high enough. It requires a proper system design to match the power consumption of air conditioning system with a proper PV size. Six solar air conditioners with different sizes of PV panel and air conditioners were built and tested outdoors to experimentally investigate the running probabilities of air conditioning at various solar irradiations. It is shown that the instantaneous operation probability (OPB) and the runtime fraction (R_F) of the air conditioner are mainly affected by the design parameter r_pL (ratio of maximum PV power to load power). The measured OPB is found to be greater than 0.98 at instantaneous solar irradiation I_T > 600 W m⁻² if r_pL > 1.71. R_F approaches 1.0 (the air conditioner is run in 100% with solar power) at daily-total solar radiation higher than 13 MJ m⁻² day⁻¹, if r_pL > 3.     

Tin and tin-based intermetallics as new anode materials for lithium-ion cells

The galvanostatic cycling behaviour of Sn/SnSb composite electrodes has been studied in 1 mol l⁻¹ LiClO₄/propylene carbonate (PC), 1 mol l⁻¹ LiPF₆/ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1), and 1 mol l⁻¹ LiClO₄/PC saturated with trans-decalin (t-Dec). Capacities between 500 and 600 mA h g⁻¹ (with respect to the mass of active material) were obtained. Reasons for the irreversible capacities are given and film formation on lithium storage metals and alloys is discussed. The observed coulombic efficiencies were slightly higher for the EC-containing electrolyte than for the PC-based one. Alternatively, improved efficiencies and stand-time behaviour were obtained when the PC electrolyte was saturated with t-Dec, which acts as a surfactant.     

Modulating the HER-overpotential at the interface of nanostructured MoS2 synthesized via hydrothermal route: An in-situ mass-spectroscopy approach

Hydrogen evolution reaction (HER) using a new exfoliated in-situ and amine-functionalized MoS₂ prepared via a hydrothermal method, assisted with sonication treatment, is reported. Techniques such as XRD, RAMAN, FTIR, XPS, N₂-physisorption and HRTEM, confirmed the production of different MoS₂ samples. Depending on the material, the overpotential for HER was modified; this was also observed for selected samples concerning the acid solution (HNO₃, H₂SO₄, HCl, and HClO₄), as demonstrated using linear sweep voltammetry and Tafel approach. The faradic current observed was in the order I_HCLO4 > I_HCl > I_H2SO4 > I_HNO3; whereas the charge-transfer resistance (ohms) was R_HNO3 (29816) > R_H2SO4 (311.5) > R_HCl (167.7) > R_HCLO4 (167.7). It was found (using DEMS) that protons (m/z = 1) modulated the generation of hydrogen (m/z = 2) at H₂SO₄, HCl, and HClO₄ solutions; conversely, at HNO₃ electrolyte, the reduction of NO₃⁻ to nitrogen was activated, delaying HER-kinetic.