PEM Fuel Cell Electrodes Prepared By Photocatalytically Deposited Pt on TiO2 and Successive Electrospinning

For successful commercialization of low temperature proton exchange membrane (PEM) fuel cells, the system should have a long life and a high performance. Further, to make them cost effective a decrease in Pt loading is also deemed necessary.

Pt supported on titania nanoparticles have shown to possess high stability. Unlike standard carbon, TiO₂ itself doesn’t corrode in fuel cell operation conditions. Also, TiO₂ is shown to form stronger bond with Pt owing to ‘strong metal support interaction’ (SMSI) [1], increasing the stability of the system itself. Due to the oxygen spillover effect, titania also acts as a co-catalyst, enhancing the oxygen reduction reaction [2]. Here, Pt/TiO₂ is prepared by reducing a Pt precursor photocatalytically under UV illumination and directly on the support [3].

Recently in another development, electrospinning was found as an efficient way to prepare porous electrodes with very low Pt loading [4]. Electrospinning facilitates the preparation of a variety of fiber networks and architectures thus enabling to achieve porous structures which are required to enhance the sluggish oxygen reduction reaction and decrease the platinum loading in a PEM fuel cell. The versatility of electrospun materials not only depends on the precursor, but also on modifying the solution and process parameters, giving a considerable control over the morphology.  

In this work, these two things are integrated together. First Nafion containing a small amount of PAA is mixed to form the electrospinning solutions with addition of Pt precursor along with titania in different amounts to obtain various loadings. In the presence of a strong source of UV light the Pt precursor is reduced to Pt and deposits itself on the TiO₂. Fig. 1 shows the scanning electron micrograph of the 20 wt.% Pt/TiO₂ catalyst held on a fibrous PAA/Nafion structure. The catalyst layer is prepared by electrospinning directly onto the GDL. The obtained catalyst layer is hot pressed on Nafion membrane to fabricate membrane electrode assembly, which will be later studied for H₂/O₂ fuel cell system. 

References:

[1]       Tauster SJ. Acc Chem Res., 20,389–94 (1987).

[2]       Diebold U. Surf Sci Rep., 48,53–229 (2003).

[3]       Ma J, Habrioux A, Alonso-Vante N. J Solid State Electrochem., 17,1913–21(2013).

[4]       Cavaliere S, Subianto S, Savych I, Jones DJ, Rozière J. Energy Environ Sci., 4,4761(2011).

Fig. 1 Scanning electron micrograph of electrospun PAA/Nafion fibers containing 20 wt.% Pt/TiO₂