La₂NiO₄ Ceramic Electrodes for Hydrogen Peroxide Electroreduction

Direct borohydride/peroxide fuel cells (DBPFCs) use sodium borohydride (NaBH₄) as an anodic fuel and hydrogen peroxide (H₂O₂) as the oxidant. DBPFCs are superior to similar types of fuel cells in terms of their theoretical cell voltage and energy density. Additionally, the fact that both fuel and oxidant reactants are liquid at ambient temperature simplifies their storage, thermal management and internal processing [1]. For these reasons, DBPFCs can be promising alternatives as power sources for space, underwater, and specific terrestrial applications where oxygen is not available.

To develop the DBPFC, we are focused on finding low-cost, stable, durable, and efficient electrocatalytic materials for H₂O₂ reduction that can simultaneously inhibit its decomposition. H₂O₂ decomposition is known to proceed even on platinum, which is the most commonly used electrocatalyst. Recently, some perovskite-type oxides were found to have reasonable activity for H₂O₂ electroreduction in DBPFCs [2].

Here, La₂NiO₄ ceramic disks are prepared by mechanosynthesis and characterized by scanning electron microscopy and X-ray diffraction. The use of ceramic pellets as electrodes allows avoiding cross-contributions of carbon or nickel foam catalyst supports, thus preventing the influence of such effects in the evaluation of La₂NiO₄ activity.

Several electrochemical methods, namely cyclic voltammetry, chronoamperometry and chronopotentiometry, were used to investigate the electrodes activity for H₂O₂ reduction in alkaline media. These studies made possible determination of the reaction kinetic parameters as well as its coulombic efficiency. The effect of temperature on the calculated number of exchanged electrons and on the charge transfer coefficients was analyzed. Stability tests were also performed.

Then, a test laboratory DBPFC was assembled using a La₂NiO₄ cathode and main cell parameters (e.g., open circuit voltage, peak power density, cell voltage and current density at the peak) were evaluated for temperatures ranging from 25 to 65 ºC.

References

• D.M.F. Santos, C.A.C. Sequeira, Sodium borohydride as a fuel for the future, Renew. Sustain. Energy Rev. 15 (2011) 3980.

• D.M.F. Santos, T.F.B. Gomes, B. Sljukic, C.A.C. Sequeira, F.M.L. Figueiredo, Electrochemical study of perovskite cathodes for H₂O₂ reduction in direct borohydride fuel cells (in preparation).