Synthesis and evaluation of ATO as a support for Pt–IrO2 in a unitized regenerative fuel cell

Abstract: An IrO2 catalyst was prepared using a colloidal method followed by a thermal treatment. The catalyst was later mixed with Pt-Black and supported on the Sb-doped SnO2 (ATO), synthesized through the same colloidal method. ATO was investigated as a possible catalyst support in an electrode of a regenerative fuel cell (URFC), where Pt–IrO2 was used as the catalyst for the oxygen evolution and reduction reactions. The morphology and composition of the ATO support was investigated through transmission electron microscopy, X-ray diffraction (including Rietveld Refinement), BET analysis, and X-ray fluorescence. An ATO support was obtained with a highly homogeneous distribution and crystal sizes, measuring approximately 4–6 nm. The Pt–IrO2/ATO material was deposited on a Nafion 115 membrane with 0.5 mg cm−2 of catalyst loading. Pt/Vulcan XC-72 (30 wt. %, E-TEK) was used as the catalyst in the H2 compartment with a Pt loading of 0.4 mg cm−2. The electrochemical activity of the Pt–IrO2/ATO for oxygen evolution/reduction in the URFC system was investigated by AC-impedance spectroscopy, linear voltammetry, and chronoamperometry techniques. The maximum mass current activity was 1118 A g−1 at 1.8 V in proton-exchange membrane water electrolyser mode (PEMWE) and 565 A g−1 at 0.3 V in proton-exchange membrane fuel cell mode (PEMFC), both at 80 °C. The value of the round-trip energy efficiency was approximately 48% at 50 A g−1. [Copyright &y& Elsevier]