Nanoporous IrRuOX catalysts with improved activity and durability for water electrolysis

Abstract

As the renewable energy generation increases, the PEM electrolyzer has been attracting great attention due to the intermittent and instability of photovoltaic and wind generation. However, in order to commercialize PEM electrolysis, there are challenges to address such as cost and durability [1-3]. In particular, oxygen evolution reaction (OER) catalysts having an excellent activity and the durability, which can reduce the amount of catalyst in the single cell level are considered an important subject in water electrolysis reaction. To increase activity and stability for OER, IrRu-based catalysts have been intensively studied until now in water electrolysis field [4]. Nonetheless, due to the dissolution of Ru, the durability of the mixed metal oxide catalysts is considered still challenges. In this study, nanoporous IrRuOX binary catalysts were synthesized by the hard template method, for the first time using the 3-dimensional ordered mesoporous silica materials were investigated to improve the activity and stability for OER in acidic media. The synthesized metal oxides were observed that specific surface area is 230m2/g. In addition, pore size distribution suggests that meso-porosity was well-developed. So, these catalysts have the advantage for both reactant supply (H2O) and detachment for produced oxygen bubbles when the OER occurs. The TEM images for representative (IrO2)1-(RuO2)4 OER catalyst are shown in Fig.1. It seems that pores fairly were arranged uniform without bulk phases. Furthermore, through the elements mapping results, it could be the check that iridium and ruthenium were evenly located.

Fig.1 HADDF-TEM Image for the replicated-(IrO2)1-(RuO2)4 OER catalyst.

In half cell test, OER activity and stability were evaluated at 10mA/cm2 over-potential and galvanic mode, respectively. Synthesized OER catalysts displays very small over-potential of 0.26 V at 10mA/cm2. To validate OER performance for made IrRuOX catalysts, membrane electrode assembly (MEA) tests were performed at 80℃. At 1A/cm2, voltage of the MEA using replicated metal oxide was 1.8V, which is lower maximum 400mV than state of the art commercial IrO2 as OER catalyst. Electrolysis efficiency was calculated to 82.3 %, which is higher than 2020 target value (75%) of Department of Energy of USA [5].