Noble Design for Highly Active and Stable PEM Electrocatalyst Using Synergistic Interaction between Pt, TiO2 and Carbons

Abstract

As interest in climate change has increased in recent years, research on alternative energy sources is becoming more active. Fuel cells are one of the most promising electrochemical energy conversion devices that hold many advantages. In particular, polymer electrolyte fuel cells (PEMFCs) are attracting much attention due to their high power density and relatively good portability. In PEMFC systems, the main cost is due to the catalyst in terms of high cost of platinum group metals. This derives the need to understand the way how to get a highly active and stable electrocatalysts. In general, Pt/C is most widely used catalyst because it has a large surface area for platinum anchoring, high electrical conductivity, and suitable pore structure for transferring reactant and product. However, carbon support undergoes carbon corrosion which is happened thermodynamically favored in fuel cell operation conditions. This phenomenon occurs at the surface of the carbon and it makes void places under the Pt nanoparticles. This mechanism causes losing electrochemical active sites. And there are also agglomeration and sintering of Pt particles on the carbon surface. Consequentially, carbon corrosion and platinum dissolution result in reduced electrochemical surface area (ECSA) and interferes long-term operations. Thus, electrochemically stable support materials need to be developed. In various alternative material candidates, our group selected the TiO2 based support because it exhibits excellent chemical stability under severe acidic condition and offers the opportunity to modifying electronic structure of platinum particles. However, hindrances such as low electrical conductivity, catalytic activity, and surface area limit the direct use of TiO2 as a catalyst support. To remedy these drawbacks, we have designed carbon-titania composite support based electrocatalysts. These noble TiO2 – carbon hybrid support was synthesized from electrospun nanofibers and platinum nanoparticles are deposited on a support by microwave-assisted polyol process. Through our new approaches, we can obtain the electrocatalysts which have a unique 3D pore structure with higher surface area, modified electronic structure with increased intrinsic activity and extended cyclic durability.