Escherichia coli hydrogenase activity and H2 production under glycerol fermentation at a low pH

Hydrogenase (Hyd) activity and H₂ production by Escherichia coli were studied at a low pH. H₂ production at pH 5.5 under glycerol fermentation was shown to be ∼1.5-fold higher than that at pH 6.5 or above but less than that under glucose fermentation. It was inhibited by N,N′-dicyclohexylcarbodiimide: H₂ production inhibition was increased with decreasing pH and almost maximal inhibition was observed at pH 5.5. The data on H₂ production by single and double mutants with defects in different Hyd-enzymes and in fhlA gene suggest that under glycerol fermentation at a low pH, Hyd-1, Hyd-2 and Hyd-4 were operating in a reversed, non-H₂ producing mode. Moreover, a role of fhlA gene in Hyd-3 and Hyd-4 activity in H₂ production is proposed under glucose fermentation at a low pH.     

Escherichia coli wild type and hydrogenase mutant cells growth and hydrogen production upon xylose and glycerol co-fermentation in media with different buffer capacities

In this study, the new strategy for long term bio-hydrogen (H₂) production using different substrates and waste materials is presented. Growth characteristics and H₂ production were investigated upon consumption of 0.4% xylose and 1% glycerol alone (which were optimal) or their mixture by Escherichia coli BW25113 wild type parental strain (PS) and ΔhyaB, ΔhybC, ΔhycE, ΔhyfG mutants with genes deletions for key subunits of hydrogenase (Hyd)-1 to Hyd-4, respectively, in high and low buffer capacity peptone (HPM, LPM) mediums, pH 5.5 and 7.5. Overall, pH 5.5 negatively affected bacterial growth and H₂ production. At pH 7.5, apart from Hyd-3 and Hyd-4 mutants, upon growth of PS, Hyd-1 and Hyd-2 mutants drop of Pt redox electrode readings from positive (～+150 mV) to negative (of ?400 to ?550 mV) values was detected during log growth phase mentioning H₂ formation. Xylose and glycerol co-utilization did not affect PS and Hyd-1 and Hyd-2 mutant's biomass and H₂ formation during log growth phase in LPM, but ～1.5 fold stimulated these parameters, especially in HPM, pH 7.5, during prolonged 96 h bacterial growth. Roles of Hyd-3 and Hyd-4 in H₂ production; and Hyd-1 and Hyd-2 in H₂ oxidation during bacterial log growth phase were stated under xylose and glycerol co-fermenting conditions. The results obtained might be valuable for industrial long term H₂ production by bacteria using mixture of carbon sources and combining various organic waste materials.     

A note on fast protonic solid state electrochromic device: NiOx/Ta2O5/WO3−x

In the present investigation, the electrochromic properties of a fast protonic solid state device: NiO_x/Ta₂O₅/WO_3−x prepared at room temperature (300 K) is reported. The non-stoichiometric tungsten oxide thin film is prepared by reactive DC magnetron sputtering technique on ITO coated glass; the oxides of tantalum (300 nm) and nickel (100 nm) are prepared by electron beam evaporation. This proton device has a coloration efficiency of 82.4 cm²/C and coloration and bleaching time of 6 and 5 s, respectively, and a transmittance variation of 60%. The work function of WO_3−x thin films by Kelvin probe in uncolored and colored states are 4.73 and 4.30 eV, respectively.     

Hydrogen production by Escherichia coli during anaerobic utilization of mixture of lactose and glycerol: Enhanced rate and yield,prolonged production

Escherichia coli wild type has the ability to utilize lactose or the mixture of lactose and glycerol producing bio-hydrogen (H₂) at different pH values. At pH 7.5 in hyaB (lacking large subunit of hydrogenase (Hyd)-1) and hybC (lacking large subunit of Hyd-2) single mutants fermenting lactose (1 g L⁻¹) H₂ yield was ∼7- and 5-fold more, respectively, compared to the wild type. During the fermentation of lactose (1 g L⁻¹) and glycerol (10 g L⁻¹) mixture H₂ yield in wild type increased ∼3-fold, compared to fermenting lactose only. H₂ generation in wild type was monitored in batch cultures during 168 h of growth when utilizing the mixture of lactose and glycerol in all combinations of different concentration. In hyaB but not in hybC mutant H₂ evolution was detected till 240 h in the mixture of 5 g L⁻¹ lactose and 10 g L⁻¹ glycerol. The highest H₂ production rate of 21.94 mL L⁻¹ h⁻¹ was detected in hyaB mutant at pH 7.5 when 1 g L⁻¹ lactose was applied. The results showed optimized H₂ production using different mutants, lactose and its mixture with glycerol. They can be applied for renewable energy, especially bio-H₂ production.     

Ruthenium oxide films for selective coatings

Although commercial selective surfaces are already available, investigation on different deposition methods and materials still goes on at many laboratories. In this work, ruthenium oxide films upon metallic substrates are assessed for this usage. Deposition of the films was made at room temperature by either spraying or dipping method in a ruthenium chloride alcoholic solution. After deposited on titanium substrates, the films were heat-treated at temperatures between 450 and 500 °C. When deposited on no-polished substrates, such films not only exhibit a high solar absorptance (α0.98), but also a high infrared emittance (ε0.8), which yield a low selectivity (S=α/ε=1.2). By deposition of similar films on polished substrates, absorptance decreases (α0.74), but emittance significantly decreases as well (ε0.12), resulting in a net selectivity increase (S6). On the other hand, evaporating a thin (20 nm) gold film upon the surface of a coating on a no-polished substrate also improves noticeably its emittance value (ε0.16) and a lower decrease in absorptance is achieved (α0.91), resulting in a selectivity increase (S5.7). These preliminary promising results indicate the high potential for using these films as solar selective coatings, but in order to optimize such selectivity values, further work to establish a close control on the deposition parameters and the substrate roughness value, should be done.     

Escherichia coli hydrogenase 4 (hyf) and hydrogenase 2 (hyb) contribution in H2 production during mixed carbon (glucose and glycerol) fermentation at pH 7.5 and pH 5.5

Molecular hydrogen (H₂) production by Escherichia coli was studied during mixed carbon sources (glucose and glycerol) fermentation at pH 7.5 and pH 5.5. H₂ production rate (V_H2) by bacterial cells grown on mixed carbon was assayed with either adding glucose (glucose assay) or glycerol (glycerol assay) and compared with the cells grown on sole carbon (glucose or glycerol only) and appropriately assayed. Wild type cells grown on mixed carbon, in the assays with adding glucose, produced H₂ at pH 7.5 with the same level as in the cells grown on glucose only. At pH 7.5 V_H2 in fhlA single and fhlA hyfG double mutants decreased ∼6.5 and ∼7.9 fold, respectively. In wild type cells grown on mixed carbon V_H2 at pH 5.5 was lowered ∼2 fold, compared to the cells grown on glucose only. But in hyfG and hybC single mutants V_H2 was decreased ∼2 and ∼1.6 fold, respectively. However, at pH 7.5, in the assays with glycerol, V_H2 was low, when compared to the cells grown on glycerol only. At pH 5.5 in the assays with glycerol V_H2 was absent. Moreover, V_H2 in wild type cells was inhibited by 0.3 mM N,N^′-dicyclohexylcarbodiimide (DCCD), an inhibitor of the F₀F₁-ATPase, in a pH dependent manner. At pH 7.5 in wild type cells V_H2 was decreased ∼3 fold but at pH 5.5 the inhibition was ∼1.7 fold. At both pHs in fhlA mutant V_H2 was totally inhibited by DCCD. Taken together, the results obtained indicate that at pH 7.5, in the presence of glucose, glycerol can also be fermented. They point out that Hyd-4 mainly and Hyd-2 to some extent contribute in H₂ production by E. coli during mixed carbon fermentation at pH 5.5 whereas Hyd-1 is only responsible for H₂ oxidation.     

Miniaturization limits for single-chamber micro-solid oxide fuel cells with coplanar electrodes

Single-chamber solid oxide fuel cells with coplanar microelectrodes were operated in methane–air mixtures (R_mix = 2) at 700 °C. The performance of cells with one pair of NiO–YSZ (yttria stabilized zirconia) anode and (La_0.8Sr_0.2)_0.98MnO₃–YSZ cathode, arranged parallel on a YSZ electrolyte substrate, was found to be significantly dependent on the electrode width. For an interelectrode gap of 250 μm, cells with average electrode widths exceeding 850 μm could establish a stable open circuit voltage (OCV) of 0.8 V, while those with widths less than 550 μm could not establish any OCV. In the intermediate range, the cells exhibited significant fluctuations in voltage and power under our testing conditions. This behavior suggests that a lower limit to electrode dimensions exists for cells with single electrode pairs, below which neither a stable difference in oxygen partial pressure, nor an OCV, can be established. Conversely, increasing the electrode width imposes a penalty in the form of an increase in the cell resistance. However, both size limits can be circumvented by employing multiple pairs of microscale electrodes in an interdigitated configuration.     

Structural, electrical and photovoltaic characterization of Si nanocrystals embedded SiC matrix and Si nanocrystals/c-Si heterojunction devices

Thin films of Si nanocrystals (Si NCs) embedded in a silicon carbide (SiC) matrix (Si-NC:SiC) were prepared by alternating deposition of Si-rich silicon carbide (Si_1−xC_x) and near-stoichiometric SiC mutilayers (Si_1−xC_x/SiC) using magnetron cosputtering followed by a post-deposition anneal. Transmission electron microscopy and Raman spectroscopy revealed that the Si NCs were clearly established, with sizes in the range of 3–5 nm. Optical studies showed an increase in the optical band gap after annealing from 1.4 eV (as-deposited) to 2.0 eV (annealed at 1100 °C). P-type Si-NC:SiC/n-type crystalline silicon (c-Si) heterojunction (HJ) devices were fabricated and their electrical and photovoltaic properties were characterized. The diode showed a good rectification ratio of 1.0×10⁴ at the bias voltage of ±1.0 V at 298 K. The diode ideality factor and junction built-in potential deduced from current–voltage and capacitance–voltage plots are 1.24 and 0.72 V, respectively. Illuminated I–V properties showed that the 1-sun open-circuit voltage, short-circuit current density and fill factor of a typical HJ solar cell were 463 mV, 19 mA/cm² and 53%, respectively. The external quantum efficiency and internal quantum efficiency showed a higher blue response than that of a conventional c-Si homojunction solar cell. Factors limiting the cell's performance are discussed.     

Highly conducting transparent nanocrystalline Cd1−xSnxS thin film synthesized by RF magnetron sputtering and studies on its optical, electrical and field emission properties

Transparent conducting Cd_1−xSn_xS thin films have been synthesized by radio frequency magnetron sputtering technique on glass and Si substrates for various tin concentrations in the films. X-ray diffraction studies showed broadening of peaks due to smaller crystal size of the Cd_1−xSn_xS films, and SEM micrographs showed fine particles with average size of 100 nm. Sn concentration in the films was varied from 0% to 12.6% as determined from energy-dispersive X-ray analysis. The room-temperature electrical conductivity was found to vary from 8.086 to 939.7 S cm⁻¹ and corresponding activation energy varied from 0.226 to 0.076 eV. The optimum Sn concentration for obtaining maximum conductivity was found to be 9.3%. The corresponding electrical conductivity was found to be 939.7 S cm⁻¹, and the mobility 49.7 cm² V⁻¹ s⁻¹. Hall measurement showed very high carrier concentrations in the films lying in the range of 8.0218×10¹⁸–1.7225×10²⁰ cm⁻³. The conducting Cd_1−xSn_xS thin films also showed good field emission properties with a turn on field 4.74–7.86 V μm⁻¹ with variation of electrode distance 60–100 μm. UV–Vis–NIR spectrophotometric studies of the films showed not needed the optical band gap energy increased from 2.62 to 2.80 eV with increase of Sn concentration in the range 0–12.6%. The optical band gap was Burstein–Moss shifted, and the corresponding carrier concentration obtained from the shift also well matched with that obtained from Hall measurement.     

Purification and characterization of [Fe]-hydrogenase from high yielding hydrogen-producing strain, Enterobacter cloacae IIT-BT08 (MTCC 5373)

Fe-hydrogenase from Enterobacter cloacae IIT-BT08 was purified 1284 fold with specific activity of 335 μmol H₂/min/mg protein for hydrogen evolution using reduced methyl viologen as an electron-donor at 25 °C. The molecular weight of the monomeric enzyme was determined to be 51 kDa by MALDI-ToF mass spectrometry. The PI of the enzyme was 5.6 displaying its acidic nature. The optimal temperature and pH for hydrogen evolution was 37 °C and 7–7.2 respectively. The affinity constant, K_m for reduced methyl viologen was 0.57 ± 0.03 mM and that of reduced ferredoxin was 0.72 ± 0.04 μM. The enzyme contained 11.47 gm-atom Fe/mol of Fe-hydrogenase. Electron paramagnetic resonance analysis ascertained the existence of iron molecules as [4Fe–4S] clusters. The internal amino acid sequences of trypsin digested peptides of hydrogenase as determined by ESI MS/MS Q-ToF showed 80-87% identities with the respective sequences of Clostridium sp. and Trichomonas sp. hydrogenase.     

Influence of hydrogen dilution on structural, electrical and optical properties of hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared by plasma enhanced chemical vapour deposition (PE-CVD)

Hydrogenated nanocrystalline silicon (nc-Si:H) thin films were deposited from pure silane (SiH₄) and hydrogen (H₂) gas mixture by conventional plasma enhanced chemical vapour deposition (PE-CVD) method at low temperature (200 °C) using high rf power. The structural, optical and electrical properties of these films are carefully and systematically investigated as a function of hydrogen dilution of silane (R). Characterization of these films with low angle X-ray diffraction and Raman spectroscopy revealed that the crystallite size in the films tends to decrease and at same time the volume fraction of crystallites increases with increase in R. The Fourier transform infrared (FTIR) spectroscopic analysis showed at low values of R, the hydrogen is predominantly incorporated in the nc-Si:H films in the mono-hydrogen (SiH) bonding configuration. However, with increasing R the hydrogen bonding in nc-Si:H films shifts from mono-hydrogen (SiH) to di-hydrogen (SiH₂) and (SiH₂)_n complexes. The hydrogen content in the nc-Si:H films decreases with increase in R and was found less than 10 at% over the entire studied range of R. On the other hand, the Tauc's optical band gap remains as high as 2 eV or much higher. The quantum size effect may responsible for higher band gap in nc-Si:H films. A correlation between electrical and structural properties has been found. For optimized deposition conditions, nc-Si:H films with crystallite size 7.67 nm having good degree of crystallinity (84% ) and high band gap (2.25 eV) were obtained with a low hydrogen content (6.5 at%). However, for these optimized conditions, the deposition rate was quite small (1.6 Å/s).     

Superprotonic KH(PO3H)–SiO2 composite electrolyte for intermediate temperature fuel cells

Novel thin film composite electrolyte membranes, prepared by dispersion of nano-sized SiO₂ particles in the solid acid compound KH(PO₃H), can be operated under both oxidizing and reducing conditions. Long-term stable proton conductivity is observed at 140 °C, i.e., slightly above the superprotonic phase transition temperature of KH(PO₃H), under conditions of relatively low humidification (pH₂O ≈ 0.02 atm).     

Microcrystallisation in Si:H: the effect of gas pressure in Ar-diluted SiH4 plasma

Using noble gas argon as a diluent of SiH₄ in RF glow discharge, undoped μc-Si:H thin films have been developed at a low power density of 30 mW/cm². It has been found that the gas pressure is a critical factor for the growth of μc-Si:H films. Undoped μc-Si:H films having σ_D10⁻⁶ S/cm and ΔE<0.57 eV have been obtained at and above a critical pressure of 0.8 Torr. When the RF power density is increased to 90 mW/cm², a more crystalline as well as highly conducting (σ_D10⁻⁴ S/cm) μc-Si:H film has been achieved at a deposition rate of 30 Å/min, which is much higher than that attained from H₂-diluted SiH₄ plasma, by conventional approach. The crystallinity of the films has been identified by the sharp Raman peak at 520 cm⁻¹ and a large number of micrograins in the TEM micrographs. The metastable state of Ar, denoted as Ar^*, plays the crucial role in inducing microcrystallisation by transferring its de-excitation energy at the surface of the growing film. A mechanism has been proposed to explain the dependence of the formation of μc-Si:H film on the working gas pressure in the plasma.     

Hydrogen production by Escherichia coli growing in different nutrient media with glycerol: Effects of formate,pH, production kinetics and hydrogenases involved

The Escherichia coli BW25113 or MC4100 wild type parental strains growth and H₂ production kinetics was studied in batch cultures of minimal salt medium (MSM) and peptone medium (PM) at pH of 5.5–7.5 upon glycerol (10 g L^?1) fermentation and formate (0.68 g L^?1) supplementation. The role of formate alone or with glycerol on growth and H₂ production via hydrogenases (Hyd) was investigated in double hyaB hybC (lacking large subunits of Hyd 1 and 2), triple hyaB hybC hycE (lacking large subunits of Hyds 1-3) and sole selC (lacking formate dehydrogenase H) mutants during 24 h bacterial growth. H₂ production was delayed and observed after 24 h bacterial wild type strains growth on MSM. Moreover, it reached the maximal values after 72 h growth at the pH 6.5 and pH 7.5. Biomass formation of the mutants used was inhibited ～3.5 fold compared with wild type, and H₂ production was absent in hyaB hybC hycE and selC mutants upon glycerol utilization on MSM at pHs of 5.5–7.5. Formate inhibited bacterial growth on MSM with glycerol, but enhanced and recovered H₂ production by hybC mutant at pH 7.5. H₂ evolution was delayed at pH 7.5 in PM, but observed and stimulated at pH 6.5 upon glycerol and formate utilization in hyaB hybC mutant. H₂ production was absent in hyaB hybC hycE and selC mutants upon glycerol, formate alone or with glycerol fermentation at pH 6.5 and pH 7.5; formate supplementation had no effect. The results point out E. coli ability to grow and utilize glycerol in MSM with comparably high H₂ yield: as well as they suggest the key role of Hyd-3 at both pH 6.5 and pH 7.5 and the role of Hyd-2 and Hyd-4 at pH 7.5 in H₂ production by E. coli during glycerol fermentation with formate supplementation. The results obtained are novel and might be useful in H₂ production biotechnology development using different nutrient media and glycerol and formate as feedstock.     

Hydrogen energy in changing environmental scenario: Indian context

This paper deals with how the Hydrogen Energy may play a crucial role in taking care of the environmental scenario/climate change. The R&D efforts, at the Hydrogen Energy Center, Banaras Hindu University have been described and discussed to elucidate that hydrogen is the best option for taking care of the environmental/climate changes. All three important ingredients for hydrogen economy, i.e., production, storage and application of hydrogen have been dealt with. As regards hydrogen production, solar routes consisting of photoelectrochemical electrolysis of water have been described and discussed. Nanostructured TiO₂ films used as photoanodes have been synthesized through hydrolysis of Ti[OCH(CH₃)₂]₄. Modular designs of TiO₂ photoelectrode-based PEC cells have been fabricated to get high hydrogen production rate (10.35 lh⁻¹ m⁻²). However, hydrogen storage is a key issue in the success and realization of hydrogen technology and economy. Metal hydrides are the promising candidates due to their safety advantage with high volume efficient storage capacity for on-board applications. As regards storage, we have discussed the storage of hydrogen in intermetallics as well as lightweight complex hydride systems. For intermetallic systems, we have dealt with material tailoring of LaNi₅ through Fe substitution. The La(Ni_l − xFe_x)₅ (x = 0.16) has been found to yield a high storage capacity of 2.40 wt%. We have also discussed how CNT admixing helps to improve the hydrogen desorption rate of NaAlH₄. CNT (8 mol%) admixed NaAlH₄ is found to be optimum for faster desorption (3.3 wt% H₂ within 2 h). From an applications point of view, we have focused on the use of hydrogen (stored in intermetallic La–Ni–Fe system) as fuel for Internal Combustion (IC) engine-based vehicular transport, particularly two and three-wheelers. It is shown that hydrogen used as a fuel is the most effective alternative fuel for circumventing climate change.     

Evidence for hydrogenase-4 catalyzed biohydrogen production in Escherichia coli

Biohydrogen production by Escherichia coli during fermentation of the mixture of glycerol, glucose and formate at different pH values was studied. Employing mutants lacking large subunits of different hydrogenases (Hyd), it was reported that, at pH 7.5, H₂ production was produced except in a hyaB hybC hycE triple mutant, thus suggesting compensatory H₂-producing functions of the Hyd enzymes. Activity of Hyd-4 was revealed in glucose assays at pH 7.5 in the triple mutant whereby 62% of the wild type level of H₂ production was derived from Hyd-4. In formate assays, it was shown, that, first, the hyaB hybC double mutant had a H₂ production ～3 fold higher than wild type, indicating that Hyd-1 and Hyd-2 oxidize H₂, and second, that at pH 5.5, Hyd-4 and Hyd-3 were responsible for H₂ production. These findings are significant when applying various carbon sources such as sugars, alcohol and organic acids for biohydrogen production.     

TiO2 thin films as protective material for transparent-conducting oxides used in Si thin film solar cells

Nb-doped TiO₂ films have been fabricated by RF magnetron sputtering as protective material for transparent-conducting oxide (TCO) films used in Si thin film solar cells. It is found that TiO₂ has higher resistance against hydrogen radical exposure, utilizing the hot-wire CVD (catalytic CVD) apparatus, compared with SnO₂ and ZnO. Further, the minimum thickness of TiO₂ film as protective material for TCO was experimentally investigated. Electrical conductivity of TiO₂ in the as-deposited film is found to be 10⁻⁶ S/cm due to the Nb doping. Higher conductivity of 10⁻² S/cm is achieved in thermally annealed films. Nitrogen treatments of Nb-doped TiO₂ film have been also performed for improvements of optical and electric properties of the film. The electrical conductivity becomes 4.5×10⁻² S/cm by N₂ annealing of TiO₂ films at 500 °C for 30 min. It is found that the refractive index n of Nb-doped TiO₂ films can be controlled by nitrogen doping (from n=2.2 to 2.5 at λ = 550 nm) using N₂ as a reactive gas. The controllability of n implies a better optical matching at the TCO/p-layer interface in Si thin film solar cells.     

Investigations of the reverse current-voltage characteristics of ITO-p CdTe heterojunction solar cells

In this paper the reverse current–voltage characteristics of a heterojunction based on spray deposited indium tin oxide (ITO) -p CdTe is presented. Particular reference is made to the study of the characteristics within the temperature intervals 120–370 K. It is established that, the reverse current–voltage characteristics have two distinct regions along the curves with the applied voltage having a strong power dependence on the reverse current at lower temperatures (I_rev U^m) . At higher temperatures however, the reverse current is directly proportional to the applied voltage (I_rev U ). Also, a possible energy band diagram to explain the current flow mechanism suggested for the reverse current in the structure is presented.     

Effect of humidity on structure and electrochromic properties of sol–gel-derived tungsten oxide films

The influence of varying relative humidity (RH55 and 75%) during thin film deposition from an oxalato-acetylated peroxotungstic acid sol by dip coating, on the microstructure and electrochromic properties of pristine tungsten oxide (WO₃) films obtained upon annealing is presented. The films fabricated under a relative humidity of 55% are amorphous whereas the ones cast under a substantially humid atmosphere (RH75%) are characterized by interconnected nanocrystallites with a triclinic phase and a nanoporous surface morphology as well. Upon lithium insertion, larger integrated values of transmission modulation and coloration efficiency are observed over the photopic and solar regions, for the films prepared under a RH75% as compared to that observed for the films deposited under a RH of 55%. Functional improvements are due to the larger surface area of nanocrystallites and a porous microstructure, a consequence of a higher degree of hydration and hydroxylation in the former films in contrast to the non-porous and a rather featureless structure of the latter films. Faster switching kinetics between the clear and blue states, a greater current density for lithium intercalation, a higher diffusion coefficient for lithium and a superior cycling stability, again shown by the film fabricated under a 75% RH confirm that the WO₃ film microstructure is most conducive for a more facile ion insertion–extraction process, which hints at its potential for electrochromic window applications.     

Magnesium ion-conducting gel polymer electrolytes dispersed with nanosized magnesium oxide

Experimental investigations are performed on novel magnesium ion-conducting gel polymer electrolyte nanocomposites based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP), dispersed with nanosized magnesium oxide (MgO) particles. The nanocomposite materials are in the form of free-standing films. Various physical and electrochemical analyses demonstrate promising characteristics of these films, suitable as electrolytes in rechargeable magnesium batteries. The optimized material with 3 wt.% MgO offers a maximum electrical conductivity of 8 × 10⁻³ S cm⁻¹ at room temperature (25 °C) with good thermal and electrochemical stabilities. The ion/filler–polymer interactions and possible conformational changes in host polymer PVdF-HFP due to the liquid electrolyte entrapment and dispersion of nanosized MgO are examined by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscopic (SEM) methods. The Mg²⁺ ion conduction in the gel film is confirmed from the cyclic voltammetry, impedance spectroscopy and transport number measurements. The Mg²⁺ ion transport number (t₊) is enhanced substantially and found to have a maximum of 0.44 for the addition of 10 wt.% MgO nanoparticles. The enhancement in t₊ is explained on the basis of the formation of space-charge regions due to the presence of MgO:Mg²⁺-like species, that supports Mg²⁺ ion motion.