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Nafion membranes were shown to be suitable substrates for atomic layer deposition (ALD) process. ALD utilising trimethyl aluminum as a precursor leads to well reproducible formation of smooth single-sided Al2O3 coating on the membranes. Physicochemical and mechanical properties of the coated membranes were compared to those of the unmodified ones. The coating reduced water uptake and thus also conductivity. Moreover, the Al2O3 coating decreased the oxygen permeability of the membrane by 10 % and the methanol permeability 30-50 %. The mechanical properties of the Nafion® membrane were improved. The resulting membranes were successfully applied in hydrogen fuel cells, direct methanol fuel cells and microbial fuel cells. In the microbial fuel cell, the Al2O3 coated membrane showed stable performance during long-term measurements of more than 100 d and doubled power densities in comparison to a cell equipped with a pristine membrane. The membrane modification strategy has potential for improving the performance of various types of membrane fuel cells and could be used for several types of functional membranes containing active groups for ALD growth.

By using sp group metals as modifiers, the catalytic properties of Pt can be improved toward alcohols oxidation. In this work we report the performance increase of direct alcohol fuel cells (DAFC) fuelled with ethanol or 2-propanol with platinum based anode electrodes modified with Bi and Sb adatoms. For example, by simply adding Sb to the Pt/C based anode ink during membrane electrode assembly fabrication of a direct ethanol fuel cell (DEFC) its performance is improved three-fold, with more than 100 mV increase in the open circuit potential. For the fuel cell fuelled with 2-propanol high power densities are obtained at very high potentials with these catalyst materials suggesting a great improvement for practical applications. Particularly in the case of Pt/C-Bi, the improvement is such that within 0.6 V (from 0.7 to 0.1 V) the power densities are between 7 and 9 mW/cm2. The results obtained with these catalysts are in the same range as those obtained with other bimetallic catalysts comprising of PtRu and PtSn, which are currently considered to be the best for these type of fuel cells and that are obtained by more complicated (and consequently more expensive) methods.

Traditionally electrodes for lithium ion batteries are manufactured using carbon additives to increase the conductivity. However, in case of lithium titanate, Li4Ti5O12 (LTO), carbon free electrodes have gathered some interest lately. Therefore two LTO materials synthesized using the same synthesis but different end milling process resulting in materials with different particle size and surface area are compared here using electrodes manufactured with and without carbon additives. Both LTO samples (LTO-SP with small primary particle size and high surface area, and LTO-LP with larger primary particle size and small surface area) produce similar capacities and voltages with or without carbon additives at low C-rates at the room temperature. However, at high C-rates and/or sub-zero temperatures electrodes with carbon additives produce higher capacities and smaller ohmic losses and this behavior is more pronounced for the LTO electrodes with smaller primary particle size and larger surface area. These results show that the feasibility of carbon free LTO electrodes depends on the properties of LTO affecting the morphology of the electrode and consequently, the transport properties. This is most pronounced under conditions where electron and Liþ ion transfer become limiting (high C-rates and low temperature).

Two different Li4Ti5O12 materials were investigated: smaller primary particle size forming large secondary particle aggregates (LTO-SP, surface area 22 m2/g) and larger primary particle size with less secondary particle aggregates (LTO-LP, surface area 7 m2/g). Both samples were synthesized using the same high temperature solid state synthesis but different end processing, resulting in same crystalline structure but different particle morphology. At 0.1C measured discharge capacities were close to the theoretical capacity of Li4Ti5O12 (175 mAh/g) and similar capacities were obtained at low C-rates and room temperature for both LTO-SP and LTO-LP. However, higher capacities were obtained with LTO-SP at high C-rates and -20 °C indicating beneficial effect of small particle size and large surface area. Shapes of the charge/discharge curves were different for LTO-SP and LTO-LP and this is attributed to the large surface area of LTO-SP which affects the electrochemical performance because of different reaction potentials at surface sites vs. bulk.