Optimum structural properties for an anode current collector used in a polymer electrolyte membrane water electrolyzer operated at the boiling point of water

Abstract

This study attempts to optimize the properties of the anode current collector of a polymer electrolyte membrane water electrolyzer at high temperatures, particularly at the boiling point of water. Different titanium meshes (4 commercial ones and 4 modified ones) with various properties are experimentally examined by operating a cell with each mesh under different conditions. The average pore diameter, thickness, and contact angle of the anode current collector are controlled in the ranges of 10-35 µm, 0.2-0.3 mm, and 0-120°, respectively. These results showed that increasing the temperature from the conventional temperature of 80°C to the boiling point could reduce both the open circuit voltage and the overvoltages to a large extent without notable dehydration of the membrane. These results also showed that decreasing the contact angle and the thickness suppresses the electrolysis overvoltage largely by decreasing the concentration overvoltage. The effect of the average pore diameter was not evident until the temperature reached the boiling point. Using operating conditions of 100°C and 2 A/cm 2 , the electrolysis voltage is minimized to 1.69 V with a hydrophilic titanium mesh with an average pore diameter of 21 µm and a thickness of 0.2 mm.

Water Electrolysis Using a Porous IrO2/Ti/IrO2 Catalyst Electrode and Nafion Membranes at Elevated Temperatures

“…Various methods have been reported to improve the assembly of the oxygen evolution catalyst IrO 2 and the membrane [ 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. However, PFSA ionomers [ 17 ], which have low glass transition temperatures, and carbon [ 8 ], which is unstable at high overvoltages, are not suitable for the oxygen evolution side of elevated temperature water electrolysis cells.…”

“…This is due to improvements in the catalyst electrode activity [ 21 , 22 , 28 ] and the conductivity of the electrolyte membrane and the decrease in the interfacial resistance ( Figure 3 and Table 3 ) by increasing the operating temperature. In some reports, water is supplied to both sides of the cell [ 25 , 27 ], whereas in others, it is supplied to only the anode side [ 22 , 24 , 26 ]. At the same time, in some cases, steam, instead of liquid water, is supplied to the anode side [ 28 ].…”

“…At the same time, in some cases, steam, instead of liquid water, is supplied to the anode side [ 28 ]. Regarding the pressure, some cells are operated at atmospheric pressure [ 23 , 28 ], whereas others are operated under pressure [ 22 , 24 , 25 , 26 , 27 ]. The characteristics strongly depend on the evaluation method, how water is supplied to the cell, and the application of pressure to both sides, and these factors affect the efficiency and safety.…”

“…At elevated temperatures (>100 °C), for PEMWE, Nafion [ 22 , 23 , 24 , 25 , 26 ], Nafion/SiO 2 [ 22 , 27 ], Aquivion [ 28 ], and Nafion/PBI [ 23 ] membranes are used as electrolyte membranes. IrO 2 is normally used as the catalyst electrode for oxygen evolution, and Pt/C is normally used as the hydrogen evolution catalyst electrode.…”

“…IrO 2 is normally used as the catalyst electrode for oxygen evolution, and Pt/C is normally used as the hydrogen evolution catalyst electrode. Oxygen evolution catalyst electrodes are prepared by using a slurry of IrO 2 and an ionomer [ 22 , 23 , 27 ], coating IrO 2 on Ti felt [ 24 ], coating IrO 2 on a membrane [ 25 ], or electrodepositing IrO 2 on carbon paper [ 26 ]. In addition, Ti, which is stable even in highly oxidizing environments, is used for the carbon gas diffusion layer (GDL) and current collector on the oxygen evolution side [ 4 , 25 ].…”