Direct borohydride/peroxide fuel cells (DBPFCs) use sodium borohydride (NaBH₄) as an anodic fuel and hydrogen peroxide (H₂O₂) as the oxidant. DBPFCs show higher theoretical cell voltage and energy density than most low temperature fuel cells. Furthermore, the fact that both fuel and oxidant are liquids at room temperature simplifies their storage, handling, thermal management and internal processing [1]. For these reasons, DBPFCs are promising alternatives as power sources for space, underwater, and specific terrestrial applications where oxygen is not available.

To push forward the DBPFC, it is necessary to develop efficient electrocatalytic materials towards hydrogen peroxide reduction reaction (HPRR), at the lowest possible cost. Nickel (Ni) alloys were found to possess good catalytic activities for HPRR [2]. Recently, it was shown that Ni-rare earth (RE) alloys presented improved catalytic activity for hydrogen evolution reaction, at much lower cost [3]. However, nothing is known about the effects of RE elements on the electrocatalytic behavior of Ni towards the HPRR.

In this study, the HPRR is evaluated in six different Ni-RE intermetallic alloy electrodes, namely nickel-cerium (Ni-Ce), nickel dysprosium (Ni-Dy) and nickel-samarium (Ni-Sm) with 5 and 10 at.% of RE metal. The alloys were prepared by arc melting, starting from the stoichiometric amounts of the two parent metals, and analyzed by XRD and SEM coupled with EDS. The results were directly compared with single Ni electrode in the same experimental conditions.

Electrochemical experiments were performed using a standard three-electrode setup, using each of the Ni-RE alloys as a working electrode. The alloys were tested in 2 M NaOH + 0.05 M H₂O₂ aqueous electrolytes, at temperatures ranging from 25 to 45 ºC. Cyclic voltammetry (CV), linear scan voltammetry (LSV), chronoamperometry (CA), and chronopotentiometry (CP), were used to investigate the electrodes activity for HPRR reduction in alkaline media. CVs of the alloys presented a well-defined cathodic peak. Plots of peak currents and peak potentials as a function of the potential scan rate allowed calculation of the number of exchanged electrons and of the charge transfer coefficients for the studied temperature range. CA measurements demonstrated good stability of the tested systems.

References

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

2. A.E. Sanli, A. Aytaç, Electrochemistry of The Nickel Electrode as a Cathode Catalyst In The Media Of Acidic Peroxide For Application of The Peroxide Fuel Cell. ECS Trans. 42 (2012) 3.

3. D.S.P. Cardoso, L. Amaral, D.M.F. Santos, B. Šljukić, C.A.C. Sequeira, D. Macciò, A. Saccone, Int. J. Hydrogen Energy 40 (2015) 4295.