MagnéLi-Phase Ti4O7-Supported Irru-Based Catalysts for Reversal Tolerant Anode of Automotive Polymer Electrolyte Membrane Fuel Cell
Authors: Lee Seung Woo , Lee Bong Ho , Baik Chaekyung , You Eunyoung , You Dae Jong , Pak Chanho 
Published: May 2020

During the operation of a polymer electrolyte membrane fuel cell electric vehicle, various transient conditions may trigger hydrogen fuel starvation, which results in fatal degradation of anode caused by the reversal of the cell voltage in the anode. The reversal-tolerant anode (RTA) strategy has been introduced to mitigate the influence of hydrogen starvation. The RTA employs a catalyst for the oxygen evolution reaction (OER), thereby boosting the electrolysis of water and reducing the rate of the carbon oxidation reaction (COR). Many previous studies for fuel starvation phenomena suggest that the COR and MEA deterioration can be suppressed by IrO2 as an RTA catalyst. However, since the surface properties of Pt/C are different from those of IrO2, the uniform dispersion of the IrO2 in the catalyst slurry to obtain a homogeneous electrode remains a challenge. Also, the utilization efficiency of both catalysts (Pt/C and IrO2) may be decreased [1]. In view of this, we have proposed the multifunctional IrRu-based catalysts with hydrogen oxidation reaction (HOR) and OER activity [2, 3]. Ultimately, to realize a durable catalyst layer in MEA, it needs to replace from carbon materials, which is usually used as active materials support, to metal oxide. However, there are challenges to use metal oxide as catalysts support as follows: (1) low specific surface area (SSA) (2) poor electric conductivity.

To resolve these problems, meso-ATO [4], and Ti4O7 [5], which is well-known conductive metal oxide, have been investigated. In this study, commercial Ti4O7 (SSA = ~38 m2 g-1) was utilized as support and Ti4O7-supported IrRu-based catalysts were prepared by using a polyol that acts as both the solvent and reducing agent under acidic conditions.

In the electrochemical test, kinetics current for HOR of 20 wt.% IrRu4/Ti4O7 at 80 mV cm-2 is 23 mA cm-2, which is similar to the that (~ 23.04 mA cm-2) of state-of-art commercial 20 wt.% Pt/C catalyst. To confirm the catalytic effect, MEAs were fabricated by using Ti4O7-supported IrRu-based catalysts as anode catalysts and commercial PtCo/C as a cathode catalyst. Single-cell performance was evaluated at 0.6 V under 338 K and 50% relative humidity (RH), and is showed 0.645 A cm−2 for IrRu4/Ti4O7 and 0.642A cm−2 for Pt/C, respectively. Thus, the performances of MEAs comprising IrRu4/Ti4O7 is similar to the commercial Pt/C anode catalyst. Fuel starvation simulation test [3] to estimate the RTA durability reveals that the MEA with IrRu4/Ti4O7 resulted in excellent RTA durability (~5 h), which was much superior to that of Pt/C (~5 min). The obtained results are expected to promote the application of multifunctional IrRu alloy catalysts for RTA of automotive PEMFC, allowing one to replace the conventional Pt/C catalysts.

This work was supported by the Hyundai Mobis, Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20183010032380), and GRI funded by GIST in 2019.

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