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Recent studies have demonstrated the potential of bacterial cellulose (BC) as a substrate for the design of bio-based ion exchange membranes with an excellent combination of conductive and mechanical properties for application in devices entailing functional ion conducting elements. In this context, the present study aims at fabricating polyelectrolyte nanocomposite membranes based on poly(bis[2-(methacryloyloxy)ethyl] phosphate) [P(bisMEP)] and BC via the in-situ free radical polymerization of bis[2-(methacryloyloxy)ethyl] phosphate (bisMEP) inside the BC three-dimensional network under eco-friendly reaction conditions. The resulting polyelectrolyte nanocomposites exhibit thermal stability up to 200 • C, good mechanical performance (Young's modulus > 2 GPa), water-uptake ability (79-155%) and ion exchange capacity ([H + ] = 1.1-3.0 mmol g −1 ). Furthermore, a maximum protonic conductivity of ca. 0.03 S cm −1 was observed for the membrane with P(bisMEP)/BC of 1:1 in weight, at 80 • C and 98% relative humidity. The use of a bifunctional monomer that obviates the need of using a cross-linker to retain the polyelectrolyte inside the BC network is the main contribution of this study, thus opening alternative routes for the development of bio-based polyelectrolyte membranes for application in e.g., fuel cells and other devices based on proton separators.

Green electrolytes composed of kappa‐carrageenan (κ‐Cg), 1‐butyl‐3‐methyl‐1H‐imidazolium chloride ([Bmim]Cl) ionic liquid, and glycerol (Gly) are prepared in aqueous solution using a simple, clean, fast and low‐cost procedure. A flexible membrane incorporating 50% wt [Bmim]Cl and 50% wt Gly with respect to κ‐Cg exhibits the highest ionic conductivity values (8.47 × 10−4/2.45 × 10−3 S cm−1 at 20/66 °C, under anhydrous conditions, and 5.49 × 10−2/0.186 S cm−1 at 30/60 °C, at a relative humidity of 98%). Tests of room temperature air/hydrogen fuel cells incorporating κ‐Cg, κ‐Cg/Gly, and κ‐Cg/Gly/[Bmim]Cl membranes demonstrate that these predominantly protonic conductors electrolytes are particularly well suited for the design and fabrication of eco‐friendly electrochemical devices whose operation does not require the flow of gases and does not lead to water formation. These new materials have excellent application prospects in high performance (flexible) energy storage devices (supercapacitors and batteries) and electrochromic devices.

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This work reports the synthesis of nanostructured Ce1-xNixO2-δ (x = 0.05, 0.1, 0.15 and 0.2) oxides prepared by cation complexation route and with the main objective of studying their redox properties using a combination of electron microscopy, synchrotron radiation X-ray diffraction (SR-XRD) and X-ray absorption near-edge spectroscopy (XANES). The Ce1-xNixO2-δ series of nanopowders maintain the cubic crystal structure (Fm3m space group) of pure ceria, with an average crystallite size of 5-7 nm indicated by XRD patterns and confirmed by transmission electron microscopy. In situ SR-XRD and XANES carried out under reducing (5% H2/He; 5% CO/He) and oxidizing (21%O2/N2) atmospheres at temperatures up to 500 °C show a Ni solubility limit close to 15 at.% in air at room temperature, decreasing to about 10 at.% after exposure to 5% H2/He atmosphere at 500 °C. At room temperature in air, the effect of Ni on the lattice parameter of Ce1-xNixO2-δ is negligible, whereas a marked expansion of the lattice is observed at 500 °C in reducing conditions. This is shown by XANES to be correlated with the reduction of up to 25% of Ce 4+ cations to the much larger Ce , possibly accompanied by the formation of oxygen vacancies. The redox ability of the Ce 4+ /Ce 3+ couple in nanocrystalline Ni-doped ceria is greatly enhanced in comparison to pure ceria or achieved by using other dopants (e.g. Gd, Tb or Pr), where it is limited to less than 5% of Ce cations.