resumo
Typical direct liquid fuel cells (DLFCs) use a liquid fuel and O-2 as the oxidant. However, for applications where O-2 is not available (e.g., space and underwater), the gas has been replaced by H2O2 as a liquid oxidant. This work presents a study of various ceramic disc electrodes with K2NiO4 structure and nominal compositions La2NiO4, La2CuO4, La1.9Pr0.1CuO4, La1.9Sr0.1CuO4, La1.8Ce0.2NiO4, La1.9Pr0.1NiO4, La1.8Pr0.2NiO4 and La1.9Sr0.1NiO4 to assess their stability and activity for the hydrogen peroxide reduction reaction (HPRR) in alkaline media. Stability tests conducted in 2 M NaOH show that Ni and Cu are readily dissolved, as occurs for substituting elements such as Sr, in agreement with calculated Pourbaix diagrams. Such degradation affects the surface of the materials, which is depleted of transition metals. This has consequences for the ORR and HPRR activity due to formation of a La-rich passivation layer on the surface. Only La2CuO4 and La1.8Ce0.2NiO4 display HPRR activity at around -0.25 V vs. RHE. An attempt is made to correlate the composition, chemical stability and electrochemical behaviour of these materials based on known molecular-orbital models proposed for the oxygen reduction reaction.
palavras-chave
LANTHANUM COPPER-OXIDE; METAL-AIR BATTERIES; OXYGEN-REDUCTION; ELECTROCATALYTIC ACTIVITY; METHANOL OXIDATION; SODIUM-BOROHYDRIDE; PEROVSKITE STRUCTURE; PRUSSIAN BLUE; SURFACE; EVOLUTION
categoria
Chemistry; Physics
autores
Cardoso, DSP; Sljukic, B; Sousa, N; Sequeira, CAC; Figueiredo, FML; Santos, DMF
nossos autores
Diogo Miguel Franco dos Santos
Bolseiro de pós-Doutoramento
Filipe Miguel H Lebre R Figueiredo
Investigador Principal
Nuno André Carvalho Sousa
Estudante de doutoramentoProjectos
agradecimentos
The authors would like to thank Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) for PhD grant no. SFRH/BD/89670/2012 (N. Sousa), for postdoctoral research grant no. SFRH/BPD/77768/2011 (B. Sljuki) and for Investigador FCT contracts no. IF/01174/2013 (F. M. L. Figueiredo) and IF/01084/2014/CP1214/CT0003 (D. M. F. Santos). FCT is also acknowledged for a grant within project UID/CTM/04540/2013 (D. S. P. Cardoso) and funding through projects UniRCell (SAICTPAC/0032/2015, POCI-01-0145-FEDER-016422), and CICECO-Aveiro Institute of Materials (FCTUID/CTM/50011/2013), financed by national funds through the FCT/MEC, and when applicable, co-financed by FEDER under the PT2020 Partnership Agreement.