In the recent five years, the performance of alkaline membrane fuel cells (AMFCs) is greatly enhanced along with the development of alkaline electrolyte membrane and electrode technology including the ionomers and PtRu catalyst [1-3]. By replacing the Pt/C catalyst in the anode to PtRu/C catalyst, the performance of membrane electrode assembly (MEA) is improved significantly, which attributed to the lowering of hydrogen binding energy by PtRu alloy [3,4]. On the contrary, the adoption of non-platinum group metal (PGM) catalysts for hydrogen oxidation reaction (HOR) in the anode showed the very poor performance until now in the MEA level due to the very low HOR activity [1,5]. Thus, the further investigation of HOR catalysts with PGM having high activity and durability under alkaline condition is demanded. Among the PGM, recently, Ir and Ru have been received increasing attention as an alternative for the Pt catalyst for HOR because of their comparable exchange current density to that of Pt [1]. Recently, alloying of Ir and Ru provide the enhancement of HOR activity under alkaline condition in the half-cell evaluation [6,7]. In addition, Ir₁Ru₁ nanowire supported on carbon catalyst displayed the higher performance as an anode catalyst than that of Pt/C catalyst in the MEA level [8].

In this study, the effect of metal loading of Ir₁Ru₄ alloy supported on carbon support on the MEA performance is investigated. The metal loading of Ir₁Ru₄ alloy is increased to 60 wt.% by repeating twice the impregnation and reduction processes for 30 wt.% loading, which applied to mitigate the enlargement of IrRu alloy nanoparticle when the metal loading increase from 30 wt.% to 60 wt.%. The MEA performance of 30 wt.% and 60 wt.% Ir₁Ru₄/C catalyst as a HOR catalyst is investigated by making the anode (0.4mg/cm²) using a spray fabrication method. The current density at 0.6V is increased from the 0.6 to 0.93 A/cm² by increasing the metal loading in the supported Ir₁Ru₄ alloy catalysts, which indicates the thickness of electrode is one factor for enhancing the MEA performance. In addition, the optimum ionomer to catalyst ratio is obtained as 0.3 for the 60 wt.% Ir₁Ru₄/C catalyst, which showed slightly better MEA performance than that of 40 wt.% Pt.

This work was also supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science and ICT (Grant NRF-2018M1A2A2063172 and NRF-2018M1A2A2063174).

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