An Effective Route to Enhance Pt/C Electrocatalyst Durability through Addition of Ceramic Nanoparticles to Facilitate Pt Redeposition.

Abstract

Platinum particle growth during long-term operations is one of the well-known bottlenecks offsetting the performance and stability of Pt-based electrocatalysts in polymer electrolyte membrane (PEM) fuel cells and PEM water electrolyzers. In this research, the addition of certain ceramic nanoparticulate additives to the catalyst ink was evaluated as a means of improving the electrochemical stability of a carbon-supported platinum (Pt/C) electrocatalyst in gas diffusion electrodes (GDEs) during an accelerated stress test (AST). GDEs prepared using three nanoparticulate ceramic additives (TiN, ATO, and TiO2) with three loadings (replacing 5, 10, and 15 wt % of the catalyst) were studied for their electrochemical performance, i.e., the initial electrochemical surface area (ECSA) and stability during AST in a liquid cell. TiN appeared to be an optimal additive among the three to (i) improve the stability by ∼40% during 1600 cycles, (ii) prohibit Pt nanoparticle agglomeration due to coalescence and Ostwald ripening, and (iii) reduce Pt dissolution during the AST, without compromising a high initial ECSA. The fundamental mechanism lies in the fact that the ceramic nanoparticles can act as additional nucleation sites for redeposition of the dissolved Pt during AST; X-ray photoelectron spectroscopy (XPS) indicates strong interactions between platinum and ceramic nanoparticles. Eventually, the superior sample was used as the cathode catalyst in an electrolyzer to compare the electrochemical performance with that of a commercial Pt/C sample. As confirmed by single-cell tests in this research, the method studied and the associated concept here to enhance the durability of Pt-based electrocatalysts are facile and scalable and hence may be readily adopted by relevant stakeholders.