High Performance Pd-CeO2-Nanorods/G Catalyst for the ORR and Its Application in a Microbial Fuel Cell

Abstract

Nanostructured Pd-CeO2-NR/G, synthesized with NaBH4 as reducing agent, was evaluated as cathode catalyst for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH and in a Microbial Fuel Cell (MFC) with pH=9.6. Previously, ceria nanorods (CeO2-NR) were synthesized by a hydrothermal method, while graphene (G) was obtained by mechanical milling. Morphological characterization showed agglomerated Pd nanoparticles and CeO2-NR dispersed over graphene. Evaluation of catalytic activity for the ORR in half cell showed a higher mass activity of Pd-CeO2-NR/G relative to Pd/C. The MFC was of the two-chamber type, separated by a Nafion(R) 117 membrane. In the anode, residual water directly from a pharmaceutical company (pH=9.6) was the electrolyte with an anode containing commercial Pt/C. The Bacilus Subtilis microorganism was used to form a biofilm over Pt/C and promote the bioelectrochemical reactions in N2 atmosphere. In the cathode chamber, KOH with pH=9.6 was the electrolyte, which was saturated with O2. The polarization curves from the MFC demonstrated a higher catalytic activity of Pd-CeO2-NR/G than Pd/C. The former delivered an open circuit voltage of 0.26 V and a maximum power density of 12.47 mW m-2.