Localized oxygen evolution and transport analysis in PEM water electrolysis on local static pressure, temperature and current density

Abstract

With the escalating severity of the global climate crisis and the strengthening global demand for carbon neutrality, hydrogen produced from renewable energy offers a pathway towards achieving carbon neutrality. To reduce the cost of eco-friendly hydrogen production, we need to increase the current density in proton exchange membrane water electrolysis for green hydrogen production, a promising technology. One problem arising from an increase in current density is that it leads to a significant generation of oxygen, resulting in mass transfer losses. However, there have been few studies on oxygen transport near the anode catalyst layer, with most studies only measuring current density. In this study, local static pressure and temperature were measured in real-time to elucidate the relationship between voltage and current. At 2.1 V (corrected voltage = 2.03 V), the static pressure amplitude is approximately −5 to 5 kPa. At 2.55 V (correction voltage = 2.41 V), it decreased by about 50 % to about −2.5 to 2.5 kPa, and the frequency became faster. With increasing voltage, the decrease in static pressure amplitude and the increase in frequency occur because oxygen rapidly increases in the catalyst layer, resulting in a reduction in residence time. At 1.65 V (corrected voltage = 1.63 V), there is little change in local static pressure, indicating the dominance of the liquid single phase. At 3.6 V (corrected voltage = 3.05 V), there is little change in local static pressure. This is due to the rapid detachment of oxygen bubbles, leading to the dominance of the gas single phase. This elucidates how oxygen bubbles are influenced by fluctuations in local static pressure, leading to the conclusion that efficient design patterns for future anode flow fields can be achieved.