Shape-tuned, surface-active and support-free silver oxygen reduction electrocatalyst enabled high performance fully non-PGM alkaline fuel cell

• Published in: RSC advances Vol. 11; no. 4; pp. 24872 - 24882
• Main Authors: Anandha Ganesh, P, Prakrthi, A. N, Selva Chandrasekaran, S, Jeyakumar, D
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 16-07-2021; The Royal Society of Chemistry
• Subjects: Anion exchanging; Catalysts; Chemistry; Electrocatalysts; Fuel cells; Islands; Morphology; Oxygen reduction reactions; Platinum metals; Potassium hydroxides; Reducing agents; Silver
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d1ra02718b

Exploring non-platinum group metal (n-PGM) based efficient oxygen reduction reaction (ORR) electro-catalysts is highly important for realizing advancement in sustainable next generation-alkaline anion exchange membrane fuel cells (AAEMFCs). Herein, we demonstrate a new "hierarchical shape tuning approach" for the synthesis of controlled sized and shaped non-PGM based Ag ORR electro-catalysts with surface active nano-islands. Hierarchical shapes ranging from spherical (S-AgNs), worm-in-sphere, sphere-in-worm and vermiform (worm-like) Ag nanostructures (V-AgNs) were obtained by precisely varying the ratios of capping agent to dual reducing agents in water at ambient conditions. Compared to S-AgNs, V-AgNs revealed a higher mass normalized ORR Tafel activity (0.303 A mg
Ag
−1
at 0.9 V), onset (1.06 V) and half wave (0.78 V) potentials and higher retention of limiting current density (>88%) after 5000 cycles in 0.5 M potassium hydroxide (KOH) solution attributable to their unique worm like morphology with surface active nano-islands and support free-nature enabled better catalyst utilization. In a fully "non-PGM AAEMFC" (n-PAAEMFC), V-AgNs exhibited the highest fuel cell activity of 115.6 mW cm
−2
and stable short-term durability (∼240 h) compared to S-AgNs (41.3 mW cm
−2
) and previously reported fully n-PAAEMFCs indicating their potential use in next-generation alkaline fuel cells.
A fully non-PGM alkaline membrane fuel cell with "highest fuel cell activity" was achieved using a hierarchically shape-tuned, small, surface-active, support-free, worm-shaped nano-structured silver oxygen reduction reaction electro-catalyst.