Proposta di ricerca Dr. Bhat:
Within the project the activity will be addressed to the development and characterisation of composite membranes
based on sulphonated perfluorinated polymers containing ceramic oxides, such as yttria doped zirconia with different
molar ratios, silica in form of MCM-41, SBA-15 and various forms of alluminosilicate for PEFC applications in the
operative conditions of high cell temperature (Tcell>100°C) and low relative humidification levels (RH<100%).
The aim of the project consists into the development of composite membranes based on Nafion ionomer able to work
without suffering the mechanical degradation phenomena typical of high temperature operative conditions.
Generally, in these conditions, the mechanical degradation occurs due to the softening of polymeric matrix and the
swelling process. In particular, this last one is due to the water presence that causes a deformation of the protonic
conduction channels with a reduction of the electrochemical performance. With the aim of limiting these problems,
the composite membranes development plays a key role because the introduction and a good distribution of
inorganic materials in the polymeric matrix produces a mechanical improvement, due to the increase of the polymer
glass transition temperature and a reduction of the swelling phenomenon, due to the a reduced water retention.
The first step will consist in the synthesis of inorganic oxides such as yttria stabilised zirconia (YSZ) in order to
investigate the optimal molar percentage of yttria to be introduced as a function of the enhanced chemical and
thermal stability of the doped material. Moreover, other inorganic materials will be procured in the class of silica or
alluminosilicates to be studied.
After a screening of the inorganic oxides to be introduced into the membranes, successively to the basic
characterisations (XRD, TEM and SEM-EDX analyses) that will define the properties of chemical stability in an
electrochemical environment, composite membranes will be prepared with a standardised casting procedure. The
obtained membranes will be characterised in terms of chemical-physical and electrochemical properties. In particular
it will be determined: the ion exchange capacity (IEC) by an acid-base titration in order to quantify the number of
exchangeable protons in the membrane; the water retention capacity through water uptake measurements in the
temperature range between 25°C-95°C; the dimensional variation in three spatial directions in the same
temperature range of water uptake measurements; the morphology of the oxides, pristine and composite
membranes by scanning electron microscopy (SEM-EDX); the proton conduction through a four-electrode method
and in a DC current by using a commercial conductivity cell in a hydrogen atmosphere.
Moreover, it will be defined a procedure for MEAs preparation including the development of novel Pt based
electrocatalysts supported on different porous carbon materials. In particular, from durability point of view, the PEFC
(single cell) will be subjected to a potential step electrochemical stressing method focusing on the carbon support
corrosion. The potential step cycling will be recorded between 1.4 V and 0.85 V vs. RHE for specific intervals of time
and potential cycles will be repeated for at least 500 cycles, so to understand the degradation mechanism of the
carbon supports.
MEAs prepared using the above mentioned materials will be characterised in a single cell configuration in order to
investigate the performance in such drastic conditions, the degradation and durability. In particular, I-V curves in the
temperature range 80-120°C at RH<100% with humidified hydrogen/air will be carried out in order to investigate
the produced power density; accelerated degradation tests at 120°C with humidified H2/air (75%RH) at 1.5 abs. bar
will be carried out by cycling electrical load and monitoring the voltage response to simulate a dynamic membrane
swelling/de-swelling behaviour during a long term test; hydrogen cross-over measurement in the above mentioned
operative conditions will be performed in order to investigate the degradation effect on tested MEAs.
Obiettivi:
This project envisages design and customization of Nafion based composite membranes for elevated temperature
and low humidity fuel cell application, establishing new types of catalyst support for enhancement of catalytic
activity towards oxygen reduction reaction. The investigation revolves around configuring above mentioned
functional materials with superior performance and better durability than the state of art components to evolve an
effective polymer electrolyte membrane fuel cell (PEMFC).
Pianificazione del lavoro
Piano di lavoro primo anno:
 Development of new Nafion-composite membrane with varying inorganic fillers such as YSZ, MCM-41, SBA-15
and various forms of aluminosilicate for low humidity PEFC applications.
 Synthesis of Pt based catalyst with porous carbon as efficient and durable support materials.
Piano di lavoro secondo anno:
 Physical, structural and electrochemical characterisation of membrane and catalyst materials and relative
screening.
 Fabrication of membrane electrode assemblies for the above said materials and performance evaluation in
fuel cell (single cell) configuration.
Piano di lavoro terzo anno:
 Durability test for the membranes, such as hydrogen cross-over, membrane thinning and delamination,
platinum sintering, platinum dissolution and deposition in the membrane, carbon-support corrosion, in the
MEAs.
 Data analysis and recommendation of materials as durable and high performance materials for fuel cell
applications.