Pt recovery using Cyphos IL-101 immobilized in biopolymer capsules

Cyphos^® IL-101, a tetraalkylphosphonium chloride salt (ionic liquid, IL) has been immobilized in capsules prepared by ionotropic gelation in calcium chloride solutions. The IL content was varied in the resin between 0.29 and 1.28 mmol IL g⁻¹. These resins have been tested for Pt recovery from HCl solutions. The equilibrium was very slightly affected by the concentration of HCl and chloride ions. The sorption isotherms were modeled using the Langmuir equation: the maximum sorption capacity was influenced by the drying of the resin but remained close to 177 mg Pt g⁻¹ for wet resin (i.e. 0.9 mmol Pt g⁻¹, dry weight basis, or 0.7 mol Pt mol⁻¹ Cyphos) and 142 mg Pt g⁻¹ for dry resin (i.e. 0.73 mmol Pt g⁻¹, or 0.57 mol Pt mol⁻¹ Cyphos). The presence of nitrates, nickel or copper ions (added under the form of chloride salts) did not significantly decrease sorption capacity even at concentrations as high as 5 g L⁻¹. Conversely, zinc at the concentration of 5 g L⁻¹, significantly decreased Pt sorption, probably due to the competition effect of chloro-anionic Zn species. This is another evidence of the ion exchange mechanism involved in the binding of hexachloroplatinate species. The kinetics are weakly affected by the agitation speed (in the range 150–350 rpm) indicating that the resistance to film diffusion is not the limiting step. The kinetics are affected by the IL content, metal concentration and more specifically the drying of the resin: intraparticle diffusion sounds to be the controlling kinetic step: the intraparticle diffusion coefficient varied between 2 × 10⁻¹² and 18 × 10⁻¹¹ m² min⁻¹, depending on experimental conditions. Platinum can be desorbed from loaded resin using either nitric acid (5 M) or thiourea (0.1 M in 0.1 M HCl acid solution). The resin was efficiently used for three sorption/desorption cycles using nitric acid: a decrease in sorption capacity and desorption efficiency was observed beginning with the third cycle, probably due to a progressive degradation of the resin.     

Electrochemical behavior of Ni(II)/Ni in a hydrophobic amide-type room-temperature ionic liquid

Electrochemical reaction of Ni(II)/Ni was investigated in a hydrophobic room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing Ni(TFSA)₂ as a Ni source. The UV–vis spectra showed that Ni(II) in BMPTFSA is octahedrally coordinated with TFSA⁻ anions. The average activation energy for the diffusion coefficients of this Ni(II) complex was 26 kJ mol⁻¹, which was close to that for the viscosity. The diffusion coefficient of Ni(II) was estimated to be 9.3 × 10⁻⁸ cm² s⁻¹. Chronoamperometric measurements showed that the electrodeposition of Ni on a platinum substrate involved three-dimensional instantaneous nucleation under diffusion control at room-temperature. The electrodeposits obtained by galvanostatic electrolysis with the current density of −0.046 mA cm⁻² at 70 and 100 °C were identified as metallic Ni by XRD.     

Thermal and mechanical properties of LaNbO4-based ceramics

Thermal and mechanical properties of polycrystalline La_1−xA_xNbO₄ (x = 0, 0.005, 0.02 and A = Ca, Sr and Ba) are reported. The materials possess a ferroelastic to paraelastic phase transition close to 500 °C, and the linear thermal expansion is significantly lower (8.6 ± 0.5 × 10⁻⁶ °C⁻¹) for the paraelastic phase compared to the ferroelastic phase (15 ± 3 × 10⁻⁶ °C⁻¹). The hardness was significantly higher for acceptor doped materials (6 GPa) compared to pure LaNbO₄ (3 GPa) due to a significantly smaller average grain size. The fracture toughness of La_0.98Sr_0.02NbO₄, measured by single edge V-notched beam method, was 1.7 ± 0.2 MPa m^1/2 independent of temperature up to 600 °C. The ferroelastic properties of the materials were confirmed by non-linear relationships between stress and strain during compression/decompression, a remnant strain after decompression and the presence of ferroelastic domains. The mechanical properties of LaNbO₄-based materials are discussed with focus on ferroelasticity, microcracking due to crystallographic anisotropy and pinning of ferroelastic domain boundaries.     

Direct oxidation of sodium borohydride on Pt, Ag and alloyed Pt–Ag electrodes in basic media. Part I: Bulk electrodes

We studied the borohydride oxidation reaction (BOR) by voltammetry for BH₄⁻ concentrations between 10⁻³ M and 0.1 M NaBH₄ in 0.1–1 M NaOH for bulk polycrystalline Pt, Ag and alloyed Pt–Ag electrocatalysts. In order to compare the different electrocatalysts, we measured the kinetic parameters and the number of electrons exchanged (faradic efficiency). BOR on bulk Pt is more efficient when the concentration of NaBH₄ increases (3e⁻ in 1 mM and 6e⁻ in 10 mM BH₄⁻/0.1 M NaOH). BOR on Pt can occur both in a direct pathway and in an indirect pathway including hydrogen generation via heterogeneous hydrolysis of BH₄⁻ and subsequent oxidation of its by-products (e.g. BH₃OH⁻ and H₂). BOR on Ag strongly depends on the pH: improved faradic efficiency is monitored for high pH (2e⁻ at pH 12.6 and 6e⁻ at pH 13.9 at 25 °C). The BOR kinetics is faster for Pt than for Ag (i_Pt=0.02 A cm⁻², i_Ag=1.4 10⁻⁷ A cm⁻² at E=−0.65 V vs. NHE in 1 mM NaBH₄/0.1 M NaOH, 25 °C) both as a result from Pt high activity regarding the BH₄⁻ heterogeneous hydrolysis and subsequent HOR, above −0.83 V vs. NHE and following direct oxidation of BH₄⁻ or BH₃OH⁻ below −0.83 V vs. NHE. Both Pt–Ag bulk alloys show unique behaviour: the number of electrons exchanged is rather high whatever the BH₄⁻ concentration and pH, while the kinetic parameters are quite similar to that of platinum, showing possible synergistic alloying effect.     

Synthesis and characterization of a polystyrenic resin functionalized by catechol: Application to retention of metal ions

Chelating solid phase extraction is a preconcentration method adapted for metal ions extraction in water and requires functionalization of a solid sorbent by an organic ligand. A new chelating resin has been prepared by grafting catechol on Amberlite^® XAD-4 with an imine bridge and reducing it to enhance stability of the modified resin. Synthesis was first carried out at molecular level to validate experimental conditions, optimize yields and facilitate characterization of solid sorbent (particularly by FTIR). Each synthesis step of grafting on Amberlite^® XAD-4 was characterized by FTIR, Py-GC–MS and TGA-DSC. BET measurements showed a decrease in specific area after grafting from 865 to 425 m² g⁻¹ and in total pore volume from 1.19 to 0.66 cm³ g⁻¹. The grafting rate of 33% was determined by back titration of –OH (0.31 ± 0.03 mmol g⁻¹ of resin) and –NH-functions (0.93 ± 0.02 mmol g⁻¹ of resin). The increase in the sorbent hydrophilicity was confirmed by evaluating the water regain. Finally the retention properties of Cd(II), Cu(II), Ni(II) and Pb(II) were determined by ICP-AES at a pH range from 2 to 9. Retention rates of 94% and 98% were found at pH 8 for Cu(II) and Pb(II), respectively. Sorption capacities of 25.8 ± 2.5 μmol g⁻¹ for Cd(II), 89.7 ± 8.4 μmol g⁻¹ for Cu(II), 49.0 ± 10.5 μmol g⁻¹ for Ni(II) and 31.5 ± 1.6 μmol g⁻¹ for Pb(II) were measured.     

Impact of supercritical drying and heat treatment on physical properties of titania/silica aerogel monolithic and its applications

TiO₂–SiO₂ monolithic aerogels were homogeneously prepared using sol–gel method. Critical point of drying of TiO₂–SiO₂ gels with ethanol was studied for 30, 60, 90 and 120 min. Subsequently, the gels were dried with supercritical ethanol, resulting in amorphous aerogels that crystallized following heat treatment at 550 °C from 1 to 5 h. The TiO₂–SiO₂ aerogels were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface area measurements. The molar ratio of SiO₂:TiO₂ was 6 and the synthetic strategy revealed that TiO₂–SiO₂ aerogel, had a surface area 868 m²/g, particle size 40 nm, density 0.17 g/cm³ and 80% porosity. The finding indicated that from economic point of view, TiO₂–SiO₂ gel should be supercritical dried for 30 min and heat-treated for 5 h. The TiO₂–SiO₂ aerogel monoliths photocatalyst synthesized using sol–gel method provided insight into the characteristics that make a photocatalyst material well-suited for photodegradation of phenol and cyanide in an industrial waste stream containing Cl⁻, S²⁻ and NH₄⁺. Interestingly, after multiple reuse cycles (i.e. ≥7), photodegradation systems with regenerated photocatalyst showed a slightly decreasing of photoactivity 2–4%. The overall kinetics of photodegradation of either phenol or cyanide using TiO₂–SiO₂ aerogel photocatalyst was found to be of first order.     

Photodegradation of tetrahalobisphenol-A (X = Cl, Br) flame retardants and delineation of factors affecting the process

The photoassisted degradation (HPLC-UV absorption), dehalogenation (HPLC-IC) and mineralization (TOC decay) of the flame retardants tetrabromobisphenol-A (TBBPA) and tetrachlorobisphenol-A (TCBPA) were examined in UV-irradiated alkaline aqueous TiO₂ dispersions (pH 12), and for comparison the parent bisphenol-A (BPA, an endocrine disruptor) in pH 4–12 aqueous media to assess which factor impact most on the photodegradative process. Complete degradation (2.7–2.8 × 10⁻² min⁻¹) and dehalogenation (1.8 × 10⁻² min⁻¹) of TBBPA and TCBPA occurred within 2 h of UV irradiation, whereas only 45–60% mineralization (2.3–2.7 × 10⁻³ min⁻¹) was complete within 5 h for the flame retardants at pH 12 and ca. 80% for the parent BPA. Factors examined in the pH range 4–12 that impact the degradation of BPA were the point of zero charge of TiO₂ particles (pH_pzc; electrophoretic method), particle or aggregate sizes of TiO₂ (light scattering), and the relative number of OH radicals (as DMPO–OH adducts; ESR spectroscopy) produced in the UV-irradiated dispersion. Dynamics of BPA degradation (2.0–2.4 × 10⁻² min⁻¹) were pH-independent and independent of particle/aggregate size, but did correlate with the number of OH radicals, at least at pHs 4 to 8–9, after which the rates decreased somewhat at pH > 9 with decreasing adsorption owing to Coulombic repulsive forces between the very negative TiO₂ surface and the anionic forms of BPA (pK_as ca. 9.6–11.3), even though the number of OH radicals continued to increase at the higher pHs.     

Selective precipitation of cadmium from nickel cadmium sulphate solutions using sodium decanoate

Each year in France, about 1300 tons of spent Ni–Cd batteries are collected. Their treatment consists of crushing, physical separation, acidic leaching of electrode materials, separation and recovery of metals leached with different processes. In this work, the selective precipitation of cadmium in synthetic Ni–Cd mixtures was investigated using sodium decanoate as precipitant. A factorial design of experiments was used to improve the separation using variables such as cadmium concentration, pH, molar ratio between decanoate and cadmium, time of addition of precipitant and rest time of the solution. In the best conditions defined by a 2⁵⁻² fractional factorial design, starting with concentrations of 0.1 mol L⁻¹ of nickel (5.9 g L⁻¹) and 0.05–0.15 mol L⁻¹ of cadmium (5.6–16.8 g L⁻¹) it is possible to recover in only one stage about 99% of cadmium without precipitating more than 5% of nickel. The results of the separation are on one side a pure solution of nickel at 2.39 × 10⁻² mol L⁻¹ (1.4 g L⁻¹) containing 3.44 × 10⁻⁴ mol L⁻¹ of cadmium (about 40 mg L⁻¹) and on the other side a precipitate of cadmium decanoate with a cadmium content equal to 23.6 wt% and nickel content lower than 0.8 wt%. These results demonstrated the viability of this separation.     

Bacterial inactivation and organic oxidation via immobilized photo-Fenton reagent on structured silica surfaces

A woven inorganic silica fabric loaded with Fe-ions (EGF-Fe) was tested under simulated solar light during hydroquinone degradation. The abatement of hydroquinone was observed to attain about 80% within 3 h. The photo-catalyst was also tested to inactive Escherichia coli K12 at “natural” pH and in the presence of a low concentration of H₂O₂. Addition of H₂O₂ (10 mg L⁻¹) did not by itself to bacterial inactivation. Total bacterial inactivation was mediated by EGF-Fe fabrics in the presence of H₂O₂ (10 mg L⁻¹) under solar light irradiation. A sample containing active (culturable) bacteria (10⁵ CFU mL⁻¹) decreased to values <1 CFU mL⁻¹ within 3 h reaction. Fe-mediated homogeneous process decreased the bacterial CFU content by about two orders of magnitude within 4 h. During the degradation of hydroquinone only a small amount of iron ions were found in solution of about 1.2 mg L⁻¹, within 90 min decreasing to values ≤0.5 mg L⁻¹ after 180 min. The leaching of Fe-ions did not affect the photo-catalyst performance since EGF-Fe fabric did not deactivate after five or more cycles. The Fe-ions founds in solution mineralized hydroquinone to levels below 37% of its initial content. The present study presents the first report on the beneficial role of a heterogeneous iron supported catalyst leading to efficient bacterial inactivation in aqueous solution with iron leaching <0.1 mg L⁻¹, the detection limit for Fe-analysis in solution. No bacterial re-growth was observed during a post-irradiation period up to 24 h in the dark.     

The effect of graphitization catalyst on the structure and porosity of SiC derived carbons

A number of carbide-derived carbon (CDC) samples were synthesized through the reaction between α-SiC and gaseous chlorine at temperatures 900, 1000 and 1100 °C and by varying the amount of catalyst. The chlorides of Co(II), Ni(II) and Fe(III) were used as catalytic additives in a range of concentration of 0.1–5 wt%. The structural differences of the obtained carbons were studied by low-temperature nitrogen adsorption, X-ray diffraction and Raman spectroscopy. Results showed that porosity, specific surface area and graphitization degree of the CDC materials is a function of chlorination temperature and catalyst concentration, which agrees with previous results. It was shown that the catalytic graphitization only weakly influences the L_a value of the crystallites, which according to the Raman scattering is 4–5 nm in both the highly disordered SiC derived carbons and in fully graphitic carbons made from SiC containing 15 wt% of surface-contacted Co–Ni–Fe catalyst. The surface area of the CDC materials can be controlled in the range of 300–1350 m² g⁻¹, depending on the amount of catalysts used.     

Fabrication and properties of highly transparent Tm3Al5O12 (TmAG) ceramics

Highly transparent Tm₃Al₅O₁₂ (TmAG) ceramics were fabricated by solid-state reaction and vacuum sintering. Densification, microstructure evolution, mechanical, thermal, and optical properties of the TmAG ceramics were investigated. Fully dense TmAG ceramic with average grain size of 15 μm was obtained by sintering at 1780 °C for 20 h. The in-line transmittance was 80.5% at 2000 nm. The absorption coefficients at 682 nm and 785 nm were 8.03 cm⁻¹ and 8.33 cm⁻¹, respectively. The Vickers hardness, the Young modulus, the bending strength, and the fracture toughness values were 15.14 GPa, 343 GPa, 230 MPa, and 2.35 MPa m^1/2, respectively. The thermal conductivity at room temperature was 3.3 W/m K and the average linear thermal expansion coefficient from 20 °C to 1000 °C was 8.915 × 10⁻⁶ K.     

Electrocatalytic ammonia synthesis: Role of cathode materials and reactor configuration

Ammonia was synthesized by reducing / over several bimetallic surfaces, supported on H⁺ conducting Nafion-117 polymer. When Pd was used alone as a cathode, the cent percent product was ammonia but the process was kinetically unfavorable (2.3 × 10⁻³ min⁻¹) during nitrite reduction. Under the same experimental conditions, Pt–Pd, Ni–Pd, Ag–Pd and Cu–Pd cathodes were mainly selective to (69–82%) but nitrite reduction activity was still low (8.1 × 10⁻³ min⁻¹). The Rh–Pd was only one cathode, which simultaneously enhanced nitrate (21.1 × 10⁻³ min⁻¹) and nitrite (25.6 × 10⁻³ min⁻¹) reduction yielding ca. 75% of . The cyclic voltammetric investigations as well as catalytic hydrogenation experiments indicated that the surface to substrate electron transfer reaction was the main reason of ammonia formation. It was noticed that multi functional roles of the Nafion membrane enhanced the ammonia synthesis performance of the electrolyte reactor.     

Poly (acridine orange) film modified electrode for the determination 1-naphthol in the presence of 2-naphthol

The voltammetric behavior of 1-naphthol was studied with a poly (acridine orange) (PAO) film modified glass carbon electrode (GCE). The electrooxidation of 1-naphthol was an irreversible process with its oxidation overpotential at the PAO electrode 180 mV lower than that on the GCE. PAO electrode demonstrated electrocatalytic activity to the electrooxidation of 1-naphthol giving a greatly improved detection limit down to 8 × 10⁻⁸ mol L⁻¹(S/N = 3). At the optimal experimental condition, the oxidation peak current from the PAO electrode was linearly proportional to the concentration of 1-naphthol in the range of 2 × 10⁻⁷ to 3.2 × 10⁻⁶ mol L⁻¹ and 5.2 × 10⁻⁶ to 1.2 × 10⁻⁴ mol L⁻¹. The differences of the oxidation peak potentials between 1-naphthol and the coexisted 2-naphthol was 170 mV allowing the selective detection of 1-naphthol in a mixed solution with 2-naphthol. The detection of 1-naphthol in tap water and river water was carried out with satisfactory results.     

Multi-walled carbon nanotubes (MWCNTs) and room temperature ionic liquids (RTILs) carbon paste Er(III) sensor based on a new derivative of dansyl chloride

Solution studies showed the strong interaction of [5-(dimethylamino) naphthalene-1-sulfonyl 4-phenylsemicarbazide] (NSP) with Er(III) ions. NSP was used as a sensing material during construction of carbon paste Er(III) sensors. The electrodes were modified with 1-n-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF₄, as room temperature ionic liquid (RTIL) and multi-walled carbon nanotube (MWCNT). Potentiometric sensors constructed with [bmim]BF₄ and MWCNTs show better sensitivity, selectivity, response time, and response stability compared to Er(III) carbon paste sensors. The best performance for the modified sensor was obtained with an electrode composition of 20% [bmim]BF₄, 20% NSP, 45% graphite powder and 15% MWCNT. This particular sensor formulation exhibits a Nernstian response (19.8 ± 0.3 mV decade⁻¹) toward Er(III) ions in the range of 1.0 × 10⁻⁷ to 1.0 × 10⁻¹ mol L⁻¹ with a detection limit of 5.0 × 10⁻⁸ mol L⁻¹. The proposed modified Er(III) sensor can be used over the pH range from 3.5 to 9.0.     

The role of DNA in PANI–DNA hybrid: Template and dopant

We exposed a novel method by using DNA as the dopant as well as template at the same time to prepare PANI–DNA hybrid micro/nanowires with conductivity as high as 10⁻² S cm⁻¹. The high conductivity is due to the co-doping function of DNA with HCl produced by FeCl₃. It is found that the morphology and conductivity of the PANI–DNA hybrids are affected by the [DNA]/[AN] ratio due to the co-operation and competition of DAN's dopant and template function, and the role of DNA in PANI–DNA hybrid varies with the changing of [DNA/[AN] ratios.     

A quantitative electron-microscopic investigation of α-phase lamellae in isotactic polypropylene fractions

Lamellar thicknesses and cross-hatching frequencies in α-isotactic polypropylene have been measured for two series of fractions using linear nucleation to provide large arrays of oriented lamellae in row structures for sampling. One series is of high tacticity polymers differing in molecular mass from 6 × 10⁴ to 8 × 10⁵, the other has low and high tacticity materials for 9 × 10⁴ and 2 × 10⁵ masses. These have allowed the differing influences of both molecular mass and tacticity to be evaluated. Lamellar thicknesses increase with molecular mass to 5 × 10⁵ then level off. This is consistent with the fold surface increasing its free energy by 20% for longer molecules as its structure becomes progressively more complex. Except for the lowest fraction, the thickness of cross-hatching lamellae is less than that of its radial neighbours because of differential thickening. The frequency of cross-hatching is greatest for the least tactic fraction but decreases linearly with molecular length. This dependence suggests that chain ends play a key role in initiation probably by laying down the first segment in epitaxial orientation. This suggestion could also account for the reduced thermal stability of spherulite centres and regions of high cross-hatching density where there is competition for chain ends between thickening and cross-hatching. The curvature of lamellae at the very end of a row mirrors the dependence of lamellae thickness with molecular mass and allows cilia pressure, the factor strongly involved in causing the lamellar divergence underlying spherulitic growth, to be estimated as 100 Pa.     

Direct synthesis of graphitic carbon nanostructures from saccharides and their use as electrocatalytic supports

An easy method is described for fabricating graphitic carbon nanostructures (GCNs) from a variety of saccharides; i.e., a monosaccharide (glucose), a disaccharide (sucrose) and a polysaccharide (starch). The synthesis scheme consists of: (a) impregnation of saccharide with Ni or Fe nitrates, (b) heat treatment under inert atmosphere (N₂) up to 900 °C or 1000 °C and (c) oxidation in liquid phase to selectively recover the graphitic carbon. This procedure leads to GCNs with a variety of morphologies: nanopipes nanocoils and nanocapsules. Such GCNs have a high crystallinity, as shown by TEM/SAED, XRD and Raman analysis. The GCNs were used as supports for platinum nanoparticles, which were well dispersed (Mean Pt size  2–3 nm). Electrocatalysts thus prepared have electrocatalytic surface areas in the 70–95 m² g⁻¹ Pt range and exhibit high catalytic activities towards methanol electrooxidation.     

Electrochemical behaviour of N-acetyl-l-cysteine on gold electrode—A tentative reaction mechanism

The electrochemical behaviour of N-acetyl-l-cysteine (NAC) has been investigated by linear and cyclic voltammetry on gold electrode at room temperature. The results showed two oxidation peaks under acid and neutral conditions and only one in basic medium. For each oxidation, as many electron was exchanged as proton. The influence of both the concentration and the potential scan rate on the peak currents highlighted a diffusion-controlled phenomenon for the first peak and an adsorption-limited reaction rate for the second one. The diffusion coefficient of NAC in solution and the surface concentration of the adsorbed species at pH 3 and 7 were close to 2 × 10⁻⁴ to 2 × 10⁻⁵ cm² s⁻¹ and 6 × 10⁻⁹ to 6 × 10⁻¹⁰ mol cm⁻², respectively. Film transfer experiments resulted in an irreversible adsorption of NAC on gold electrode, and the formation of a self-assembled monolayer (SAM).     

Good temperature stability of K0.5Na0.5NbO3 based lead-free ceramics and their applications in buzzers

(K_0.5−xLi_x)Na_0.5(Nb_1−ySb_y)O₃ (KLNNSx–y, x = 0–4 mol% and y = 0–8 mol%) lead-free piezoelectric ceramics were prepared by the conventional mixed oxide method. The denser microstructure and better electrical properties of the ceramics were obtained as compared to the pure K_0.5Na_0.5NbO₃ ceramic. The temperature stability of the electrical properties of the ceramics was also investigated. The experimental results show that the KLNNS2.5–5 ceramic exhibits good electrical properties (k_p  49%, k₃₁  30% and , tan δ  0.019), and possesses good temperature stability in the temperature range of −40 to 85 °C. The related mechanisms for improved electrical properties and temperature stability were also discussed. Moreover, buzzers based on the KLNNS2.5–5 ceramic have been fabricated and their characterization is presented. These results show that the KLNNS2.5–5 ceramic is a promising lead-free material for practical application in buzzers.     

The role of particle size on the electrochemical properties at 25 and at 55 °C of the LiCr0.2Ni0.4Mn1.4O4 spinel as 5 V-cathode materials for lithium-ion batteries

The role of the particle size on the electrochemical properties at 25 and at 55 °C of the LiCr_0.2Ni_0.4Mn_1.4O₄ spinel synthesized by combustion method has been determined. Samples with different particle size were obtained by heating the raw spinel from 700 to 1100 °C, for 1 h in air. X-ray diffraction patterns revealed that all the prepared materials are single-phase spinels. The main effect of the thermal treatment is the remarkable increase of the particles size from 60 to 3000 nm as determined by transmission electron microscopy. The electrochemical properties were determined at high discharge currents (1C rate) in two-electrode Li-cells. At 25 and at 55 °C, in spite of the great differences in particle size, the discharge capacity drained by all samples is similar (Q_dch ≈ 135 mAh g⁻¹). Instead, the cycling performances strongly change with the particle size. The spinels with Φ > 500 nm show better cycling stability at 25 and at 55 °C than those with Φ < 500 nm. The samples heated at 1000 and 1100 °C, with high potential (E ≈ 4.7 V), elevate capacity (Q ≈ 135 mAh g⁻¹), and remarkable cycling performances (capacity retention after 250 cycles >96%) are very attractive materials as 5V-cathodes for high-energy Li-ion batteries.