| Abstract | Advanced energy storage and conversion systems such as fuel cells and metal air
batteries achieved wide attention. Oxygen reduction reaction (ORR) and Oxygen
evolution reaction (OER) are the prominent reactions that govern the charging and
discharging capability of batteries as well as fuel cells. The bifunctional electrocatalyst
that can be used to activate both the reactions (ORR and OER) are demanding and still
challenging. Platinum (Pt) group metals are found to be the most efficient
electrocatalyst, but their high cost and limited availability restrains large scale
commercialization. Intensive research focused on developing highly active, costeffective and earth abundant materials for bifunctional oxygen electrocatalyst for next
generation energy sources.
In this work, we mainly focused on the solution combustion synthesis (SCS) method
for preparing nanoparticles and studying their bifunctional electrocatalytic performance
in alkaline medium. The structure, physio-chemical nature and composition of the
material can be tuned by the synthesis condition that enables us to correlate them with
the catalytic performance for oxygen reactions.
In SCS technique, the fuel to oxidizer ratio (φ) is identified as a critical parameter
affecting the properties of the synthesized nanoparticles. In the first part of this study,
we prepare cobalt nanoparticles with different fuel ratio (φ = 0.5, 1 and 1.5). Then we synthesized bimetallic Ag-M (Cu and Co) using three different modes of SCS. The
phase distribution of the catalyst after stability shows a clear phase de-alloying and
segregation of elements that reduces the performance.
Thereafter, we focused on perovskite materials LaMO3 (M = Cr, Mn, Fe, Co, Ni) with
stable and homogeneous perovskite phases. LaMnO3 shows the maximum current
density for ORR, whereas LaCoO3 shows best performance for OER. Finally, we
focused on enhancing the surface area of perovskite by incorporating a leachable salt
(e.g. KCl) during combustion that breaks down the three-dimensional crystalline
structure to restrict post combustion agglomeration and sintering, which in-turn
translates into better electrocatalytic performance. Based on these results, we conclude
that the salt assisted SCS has the potential for preparing highly efficient and durable
bifunctional electrocatalyst suitable for fuel cells and metal air batteries. |
