Reduced graphene oxide supported ceria as co-catalysts for oxygen reduction in low platinum loading acidic fuel cells

The sluggish kinetics of oxygen reduction reaction (ORR) occurring in the cathode of proton exchange membrane fuel cell is still considered the limiting factor for large-scale commercialization of this device since the necessity of expensive Pt-based catalysts. Here, ceria-reduced graphene oxide (CeO2-rGO) is proposed as a promising additive to commercial Platinum over carbon (Pt/C) catalyst, aimed to reduce the Platinum loading and enhance the catalyst efficiency. The co-catalyst has been synthesized using a simple calcination step to get oxygen vacancies formation and graphene oxide reduction in one step. Graphene oxide, reduced graphene oxide, ceria and the final ceria-reduced graphene oxide have been characterized physico-chemically. Preliminary ex-situ electrochemical tests have been performed on Pt/C, Pt/C: CeO2 (1:1 wt: wt), Pt/C: CeO2-rGO (1:1) and Pt/C: CeO2-rGO (0.5:1). The last composition, showing the best catalytic activity for the ORR, has been also analysed in a single fuel cell prototype. The in-situ tests have demonstrated an enhance of almost 40% in power density in low humidity condition (30% at 80°C) compared to a cathode with doubled Pt-loading, suggesting the boosting role of oxygen vacancies and water retain capacity of this platinum co-catalyst.