Highly Reversal Tolerant Anodes Using Ti4O7-Supported Platinum with a Very Small Amount of Water Splitting Catalyst

Abstract

Gross fuel starvation (cell reversal) event are known to damage the anode of PEFC seriously due to exceptionally high anodic potential (> 2 V vs RHE) when the anode gas channel or manifolds are clogged with water or ice. This high potential is due to oxygen evolution and/or carbon corrosion reactions (OER & COR) at anode to generate protons, instead of hydrogen oxidation reaction. Especially, COR may lead to rapid destruction of the anode structure so that promotion of OER instead of COR would be better way to mitigate serious damages by the fuel starvation. Thus, reversal tolerant anode (RTA), which includes water splitting catalyst to promote OER is one of the solution from material side to mitigate these serious damages. So far, water splitting catalyst (iridium and/or ruthenium) mixed Pt/C has been proposed as RTA, however a significant amount of iridium is indispensable to mitigate the damages. Here we will present oxidation-resistant and electro-conductive titanium oxide (Ti4O7) supported Pt (Pt/Ti4O7) catalyst-based RTA with very small amount of Ir without compromising RTA properties. For example, MEAs using a conventional Pt/C RTA including 0.04 mgIr cm-2 showed significant voltage loss after severe cell reversal test (0.2 A cm-2 load @H2-starved anode for 7,200 seconds), however, almost no performance loss was observed for the Pt/Ti4O7 RTA including the same amount of Ir. Moreover this superior reversal tolerant property of Pt/Ti4O7 RTA was found to be kept at as low as 0.014 mgIr cm-2. Detailed data about electrochemical and post mortem analyses of the tested MEAs will be discussed at the Meeting.