Progress of elevated-temperature alkaline electrolysis hydrogen production and alkaline fuel cells power generation

Abstract

The progress of elevated-temperature alkaline electrolysis for hydrogen production and alkaline fuel cells for power generation is highlighted. Alkaline water electrolysis utilizes platinum group metals and nickel-based alloys, such as Raney nickel and stainless steel, as electrocatalysts. It employs aqueous KOH solutions or molten KOH-NaOH-LiOH as electrolytes, combined with metal oxide diaphragms fabricated via tape casting or electrode-supported powder sintering for product separation. Notably, electrolysis has demonstrated stable operation for over 400 h at temperatures between 100 and 400 °C, with a degradation rate of less than 0.1 V/kh. At the system level, a 20 kW stable water electrolysis has been achieved at 130 °C, allowing flexible transitions between endothermic and exothermic modes for multi-thermal-source thermo-hydrogen energy conversion. Elevated-temperature alkaline fuel cells, using similar electrocatalysts, have expanded their electrolyte options to include solid materials with adequate ionic conductivity, such as high-valence metal-doped phosphates. Liquid-electrolyte systems have successfully achieved kW-level applications in both terrestrial and space environments, while recent solid-electrolyte developments have demonstrated over 160 h of continuous operation, with alkaline membrane fuel cells achieving stable operation for more than 195 h.