El-Nagar, G.A.; Hassan, M.A.; Fetyan, A.; Kayarkatte, M.K.; Lauermann, I.; Roth, C.: A Promising N-doped Carbon-Metal Oxide Hybrid Electrocatalyst Derived from Crustacean’s Shells: Oxygen Reduction and Oxygen Evolution. Applied Catalysis B: Environmental 214 (2017), p. 137-147
10.1016/j.apcatb.2017.05.030
Abstract:
The development of both efficient and durable Pt-free catalysts for oxygen reduction (ORR) is extremely important to realize the world-wide commercialization of clean energy technologies, such as fuel cells and batteries, which is currently hindered by the exorbitant cost and scarcity of the state-of-the-art Pt-based catalysts. As a potential alternative to such expensive catalysts, this investigation addresses the facile synthesis of an efficient, durable and highly poison-tolerant metal-free N-doped carbon-Nd2O3 hybrid bifunctional electrocatalyst for ORR and water splitting, which has been derived from encapsulated Nd(OH)3 in the chitosan matrix (N-C/Nd2O3). Chitosan, obtained from the crustacean’s shells, assists to form a smaller Nd2O3 particle sizes and at the same time yields an efficiently nitrogen-doped graphitic structure with outstanding activity and durability for ORR in alkaline and acidic media. N-C/Nd2O3 catalyst exhibits ~50 mV positive shift in half-wave potential with a comparable onset potential and limiting current density of ORR to that of Pt/C catalyst (with same loading) in 0.1 M KOH. Additionally, N-C/Nd2O3 shows a high tolerance towards crossover of the various anodic fuels concurrent with outstanding tolerance against poisoning with various hydrocarbon impurities (e.g., acetonitrile, acrylonitrile, etc) in-situ generated during fuel cell operation. N-C/Nd2O3 activity shows only a slight attenuation of 3% after 8 h of continuous ORR and 6% in the presence of 50 ppm of acetonitrile compared with 50% and 80% observed at Pt/C. In a H2-air single cell a membrane electrode assembly (MEA) prepared from N-C/Nd2O3 as a cathode catalyst delivered a maximum power density of ~287 mW cm2 and current density of ~572 mA cm-2 at 0.6 V which is especially outstanding. The superior electrocatalytic activity and durability of the as-prepared catalysts mainly originate from the synergistic effects between Nd2O3 particles and chitosan functional groups, besides the nitrogen-doped nature of the as-prepared catalyst. Furthermore, the as-prepared catalyst shows a high activity and durability in the oxygen evolution reaction (OER) as well, making it an efficient non-precious bifunctional catalyst. The facile preparation method with metal oxide encapsulated N-doped graphitic structures from cheap, nature and ecofriendly chitosan opens up a new horizon for the world-wide commercialization of fuel cells and metal-air batteries.