Enhanced performance and durability of low catalyst loading PEM water electrolyser based on a short-side chain perfluorosulfonic ionomer

Abstract

Water electrolysis supplied by renewable energy is the foremost technology for producing “green” hydrogen for fuel cell vehicles. In addition, the ability to rapidly follow an intermittent load makes electrolysis an ideal solution for grid-balancing caused by differences in supply and demand for energy generation and consumption. Membrane-electrode assemblies (MEAs) designed for polymer electrolyte membrane (PEM) water electrolysis, based on a novel short-side chain (SSC) perfluorosulfonic acid (PFSA) membrane, Aquivion®, with various cathode and anode noble metal loadings, were investigated in terms of both performance and durability. Utilizing a nanosized Ir0.7Ru0.3Ox solid solution anode catalyst and a supported Pt/C cathode catalyst, in combination with the Aquivion® membrane, gave excellent electrolysis performances exceeding 3.2 A·cm−2 at 1.8 V terminal cell voltage (∼80% efficiency) at 90 °C in the presence of a total catalyst loading of 1.6 mg⋅cm−2. A very small loss of efficiency, corresponding to 30 mV voltage increase, was recorded at 3 A⋅cm−2 using a total noble metal catalyst loading of less than 0.5 mg·cm−2 (compared to the industry standard of 2 mg·cm−2). Steady-state durability tests, carried out for 1000 h at 1 A⋅cm−2, showed excellent stability for the MEA with total noble metal catalyst loading of 1.6 mg·cm−2 (cell voltage increase ∼5 μV/h). Moderate degradation rate (cell voltage increase ∼15 μV/h) was recorded for the low loading 0.5 mg·cm−2, MEA. Similar stability characteristics were observed in durability tests at 3 A·cm−2. These high performance and stability characteristics were attributed to the enhanced proton conductivity and good stability of the novel membrane, the optimized structural properties of the Ir and Ru oxide solid solution and the enrichment of Ir species on the surface for the anodic catalyst.