IrO_XSupported onto Niobium-Doped Titanium Dioxide as an Anode Reversal Tolerant Electrocatalyst for Proton Exchange Membrane Fuel Cells

Abstract

The addition of an oxygen evolution electrocatalyst to an anode catalyst layer is demonstrated as a practical approach to address the voltage reversal of proton exchange membrane fuel cells (PEMFCs). In this work, IrO X nanoparticles uniformly deposited on niobium-doped TiO2 (IrO X /Nb0.1Ti0.9O2) by a sol–gel method are employed as reversal tolerant anodes (RTAs) for PEMFCs. The membrane electrode assembly (MEA) with this RTA possesses a reversal tolerance time of 29.1 min, which is the best result among all the as-prepared MEAs. Meanwhile, the decrease in the cell voltage of this MEA after reversal testing is only 61 mV at a current density of 1.2 A cm–2 with a degradation rate of 11.1%. The improved reversal tolerance is attributed, in part, to the uniformly distributed IrO X nanoparticles, boosting the oxygen evolution reaction and, in part, to avoid the carbon oxidation reaction by the application of a noncarbon support. This result can lay a fundamental basis for the application of RTA based on a noncarbon support to improve the anode reversal tolerance for PEMFCs.

Improved Reversal Tolerant Properties of IrOXas an Anode Electrocatalyst in Proton Exchange Membrane Fuel Cells

“…Figure a shows the antireversal test results for three different anodes. For the standard Pt/C as the anode, the voltage reaches −2.0 V in only 2 min . The MEA with annealed IrO X results in stable cell voltage, while the MEA with pristine IrO X (without annealing) perceives a reversal tolerance (69.3 min).…”

“…The 47.1 wt % Pt/C (TEC10EA50E, Tanaka) catalyst and D520 ionomer were used to both fabricate the cathode catalyst layer (CCL) and the ACL, and the IrO X catalysts were added to the anode catalyst ink to endow the MEAs with voltage reversal tolerance. The composition ratios of catalyst inks and the fabrication process of the catalyst-coated membrane (CCM) can be found in our previous work and are not detailed here . The Pt nominal loadings for all CCLs were 0.4 mg cm –2 .…”

“…Prior to testing, the MEAs were conditioned using a procedure described in refs and . Then, the polarization curves of MEAs were measured with the same testing parameters in our previous work . Subsequently, the electrochemical impedance spectroscopy (EIS) was performed at 200 mA cm –2 , during which high-purity hydrogen and air were supplied to the anode and cathode at 0.2 and 0.2 standard liters per minute, respectively.…”

“…The composition ratios of catalyst inks and the fabrication process of the catalyst-coated membrane (CCM) can be found in our previous work and are not detailed here. 28 The Pt nominal loadings for all CCLs were 0.4 mg cm −2 . The Pt and IrO X nominal loadings for all ACLs were 0.2 and 0.1 mg cm −2 , respectively.…”

Enhancing Voltage Reversal Tolerance of Proton Exchange Membrane Fuel Cells by Tuning the Microstructure of IrOx Catalysts

“…To suppress the COR and protect the anode of the starved cells from corrosion, OER catalysts (e.g., IrO 2 ) are usually applied to the anode catalyst layers (ACLs) to make reversal-tolerant anodes (RTAs). Extensive work has been done to extend the water electrolysis platform of RTAs, thus delaying the increase of anodic potential. − However, the water electrolysis platform eventually suffered sudden death. There is still controversy about the deactivation and sudden death of the RTAs.…”