Abstract:
Renewable and clean energy resources are becoming prominent to replace the fossil fuels
which are the primary reason for the climate change. To maximize the usage of
intermittently available clean energy resources such as solar energy and wind energy, there is
an urgent need to develop efficient energy storage and conversion systems. Among the
energy storage and conversion systems hydrogen-based systems have a huge potential
because of the high energy density of fuel cells which is an important part of hydrogen
economy. However, the hindrance to the development of fuel cell technology comes from the
slow kinetics of Oxygen Reduction Reaction (ORR) occurring at the cathode of the fuel cell.
The state-of-the-art platinum electrocatalyst despite the superior electrocatalytic activity has
drawbacks of lack of stability at ORR potential ranges and high costs because of the scarcity
of noble metals. In this prospect transition metal carbides have been reported to have
platinum-like behaviour and have exemplary performance which can replace platinum as
ORR electrocatalyst. However, synthesis of transition metal carbides with combination of
high activity and long-term stability along with high specific surface area is still a challenge.
Hence, in situ crystallized high entropy carbides in a Si-based Polymer Derived Ceramic
(PDC) matrix were synthesized as prospective ORR electrocatalysts. The compositional
complexity of these multi component nanocomposites gives combined properties of
electrocatalytic activity and stability of various elements present in the material system.
Further the PDC route enables the high surface area, making them ideal for catalytic
applications. To study this type of PDC nanocomposites V, Ta, Mo, Nb, and W were chosen as
transition elements owing to its higher entropy-forming-ability (EFA) as reported earlier.
First the effect of staring polymer precursor on the structure of resulting ceramic was studied.
The results indicate that the architectures of the precursors are shown to have a prominent
role in controlling the structural features at various length scales containing these
compositionally complex high entropy carbides in Si containing ceramic matrices. Further,
SiOC based high-entropy carbide nanocomposite was chosen and an extensive study on the
phase stability of this high entropy carbide was performed with respect to synthesis
conditions. In addition, the ORR activity and stability of these nanocomposites were studied
in detail. Finally, to improve the activity and stability of these nanocomposites and extend the
scope of the synthesis route, high entropy carbide nanocomposites consisting of the transition
elements that enhance the activity along with the elements that improves the stability will be synthesized and studied for their electrocatalytic performance