US EPA

4806270 

Journal Article 

Nanostructured robust cobalt metal alloy based anode electro-catalysts exhibiting remarkably high performance and durability for proton exchange membrane fuel cells 

Pajerowski, DM; Garlea, VO; Knowles, ES; Andrus, MJ; Patel, PP; Datta, K; Velikokhatnyi, SE; Jampani, Xin; Hong, D; Poston, W; Manivannand, A; Kumta, PN 

2015 

3 

26 

14015-14032 

10.1039/c5ta01362c 

WOS:000356865300050 

In recent years, the development of durable and electrochemically active electro-catalyst alloys with reduced noble metal content exhibiting similar or better electrochemical performance than pure noble metal electrocatalysts has gathered considerablemomentumparticularly, for proton exchange membrane fuel cell (PEMFC) application. Engineering such reduced noble metal containing electro-catalyst alloys in nano-scale dimensions with highly active electrochemical surface area (ECSA) will ultimately translate to reduced noble metal loadings to ultra-low levels which will eventually lead to an overall reduction in the capital cost of PEMFCs. Herein we report the development of nanostructured Co-Ir based solid-solution electro-catalyst alloys for the hydrogen oxidation reaction (HOR) further validated by first principles theoretical calculation of the d band center of the transition metal in the solid solution alloys. The theoretical and experimental studies reported herein demonstrate that the nanostructured alloy electro-catalysts comprising 70 at% Co (Co0.7Ir0.3) and 60 at% Co (Co0.6Ir0.4) of crystallite size similar to 4 nm with a high electrochemically active surface area (ECSA) (similar to 56 m(2) g(-1)) exhibit improved electrochemical activity (reduction in overpotential and improved reaction kinetics) for the HOR combined with outstanding durability in contrast to pure Ir nanoparticles (Ir-NPs) as well as state of the art commercial Pt/C system. Moreover, an optimized alloy containing 60 at% Co (Co0.6Ir0.4) showed a remarkable similar to 156% and 92% higher electro-catalytic activity for the HOR than Ir-NPs and commercial 40% Pt/C, respectively, with similar loading and ECSA. The single PEMFC full cell study also shows similar to 85% improved maximum power density for the Co-0.6(Ir-0.4) electrocatalyst compared to 40% Pt/C and excellent electrochemical stability/durability comparable to 40% Pt/C.