Development of unsupported IrO2 nano-catalysts for PEM water electrolyzer applications

Abstract

Abstract IrO2 is a commonly used catalyst for polymer electrolyte membrane water electrolyzer (PEMWE) applications due to its high stability during the oxygen evolution reaction (OER). However, its activity needs to be significantly improved to justify the use of such a high-cost material. In this study, the activity of the IrO2 catalyst was improved by optimizing two synthesis methods i.e., the modified Adams fusion method (MAFM) and the molten salt method (MSM). Physical characterizations were done via x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and brunauer-emmett-teller (BET) analyses. The OER performances were evaluated ex-situ via cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronopotentiometry (CP) analyses. The XRD results showed that the IrO2 crystallinity and crystallite size increased with increasing temperatures. Optimum OER performances of the IrO2 catalysts were obtained at different temperatures for the two synthesis methods. For the MAFM, a synthesis temperature of 350℃ produced the IrO2 catalyst with the highest OER activity and stability. However, for the MSM, a synthesis temperature of 350℃ produced the IrO2 catalyst with the highest activity while a synthesis temperature of 500℃ produced the catalyst with the highest stability. The IrO2 catalysts showed significantly improved OER performances compared to a commercial IrO2 catalyst under the study’s test conditions.