Pt-rare earth metal alloy/metal oxide catalysts for oxygen reduction and alcohol oxidation reactions: An Overview
Pt based catalyst represents the best state-of-the-art electrocatalysts for electrochemical cathodic oxygen reduction reaction of proton exchange membrane fuel cells. Among, Pt based electrochemical catalysts, Pt-transition metal catalysts have been the most successful in terms of activity. However, the poor structural and chemical stability of Pt-based alloy catalysts is challenged. Alternatively, alloying Pt with rare earth metals is considered as one of the effective ways to discover the active and durable electrocatalysts for ORR. The advantageous of alloying with rare earth metals bring the substantial change in the electronic properties and their negative alloying energy or enthalpy of formation of alloy provides a special driving force to resist the alloy against dissolution. Challenges of Pt-rare earth alloy lies on the synthesis by a solution phase route. Till date there only physical metallurgical methods enable to synthesis them successfully in the form of alloy, which otherwise the rare earth component, results in oxides/hydroxides phase. This article reviews several studies put forward to synthesize the Pt-rare earth alloy/oxide catalysts by various physical metallurgical methods and solution-based synthesis protocol and their description on the improvement of ORR activity.