Despite over a century of study and decades of intensive research, few fuel cell products have appeared on the market. [1] The major inhibitor to mass commercialisation is cost. [2] H 2 /air alkaline fuel cells (AFCs) containing KOH(aq) electrolyte promise the lowest cost devices, [3,4] with the ability to use non-Pt catalysts. The fundamental problem with AFCs is that the KOH(aq) electrolyte reacts with CO 2 (cathode air supply) to form carbonate species, which lowers cell performance and lifetime (formation of carbonate precipitates in electrodes and reduction of OH -concentration in electrolyte). [4,5] However, the carbonate content of a aqueous-electrolyte-free (metal-cation-free) alkaline anion-exchange membrane (AAEM), that was pre-exchanged to the CO 3 2-form, decreased when operated in H 2 /air and methanol/air fuel cells. This remarkable result is contrary to prior wisdom; AAEMs inherently prevent carbonate performance losses when incorporated into AFCs. This experiment was made possible only by the recent breakthrough development of an alkaline interface ionomer, [6] which allows fabrication of membrane electrode assemblies that do not require incorporation of metal hydroxides species to perform well. [7] The widely perceived advantages of alkaline membrane direct alcohol fuel cells (AMDAFC) are the potential use of relatively inexpensive and abundant non-Pt electrocatalysts (as with the H 2 /air AFCs), [8][9][10] reduced alcohol crossover, [11,12] and enhanced electro-oxidation of high energy density alcoholic fuels. [13] However, metal hydroxides have traditionally been used as an additive, either in the electrode architectures [7] or in the aqueous alcohol supplies [11] due to the previous lack of an alkaline analogue to the perfluorosulfonic acid dispersions, [14] required for high-performance membrane electrode assemblies (MEAs) for proton-exchange membrane fuel cells (PEMFCs). Concerns persist about the effect of carbonate formation with such AMDAFCs. [15] The hypothesis that was tested in this study is that the tendency to form CO 3 2-can be reduced on the elimination of M n+ from AAEM-based solid alkaline fuel cells (SAFCs); precipitates of metal carbonates [4] cannot then form (the counter -N + R 3 cations are covalently bound to the polymer electrolyte analogous to the -SO 3 -counter anions in PEMs). The data presented in Table 1 compare the ex situ properties of the AAEM in CO 3 2-and OH -forms; the properties do not vary substantially. Importantly, the through-membrane conductivities at 30°C in a static relative humidity (RH) = 100% atmosphere were similar. The ionic performance of AAEMs would not be seriously compromised even on substantial formation of carbonate.Peak power densities of 37.9 ± 1.4 mW cm -2 were obtained in H 2 /air fuel cell tests with the AAEM MEAs in CO 3 2-form ( Figure 1); this was higher than the 32.9 ± 1.6 mW cm -2 obtained with the OH -benchmarks. The respective in situ cell resistances of 1.5 ± 0.2 Ω cm 2 and 1.7 ± 0.2 Ω cm 2 showed that there was only a small in...

Three tetravalent actinide (An ) hexanuclear clusters with the octahedral core [An (OH) O ] (An =U , Np , Pu ) were structurally characterized in the solid state and in aqueous solution by using single-crystal X-ray diffraction, X-ray absorption, IR, Raman, and UV/Vis spectroscopy. The observed structure, [An (OH) O (H O) (HDOTA) ]⋅HCl/HNO ⋅n H O (An=U(I), Np(II), Pu(III)), consists of a An hexanuclear pseudo-octahedral cluster stabilized by DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) ligands. The six actinide atoms are connected through alternate μ -O and μ -OH groups. Extended X-ray absorption fine structure (EXAFS) investigations combined with UV/Vis spectroscopy provide evidence for the same local structure in moderate acidic and neutral aqueous solutions. The synthesis mechanism was partially elucidated and the main physicochemical properties (pH range stability, solubility, and protonation constant) of the cluster were determined. The results underline the importance of: 1) considering such polynuclear species in thermodynamic models, and 2) competing reactions between hydrolysis and complexation. It is interesting to note that the same synthesis route with thorium(IV) led to the formation of a dimer, Th (H O) (H DOTA) ⋅4 NO ⋅x H O (IV), which contrasts to the structure of the other An hexamers.

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