A low-temperature electro-thermochemical water-splitting cycle for hydrogen production based on LiFeO2/Fe redox pair

Abstract

The thermochemical water-splitting cycles have been paid more attention in recent years because they directly convert thermal energy into stored chemical energy as H2. However, most thermochemical cycles require extremely high temperatures as well as a temperature switch between reduction and oxidation steps, which are the main obstacles for their development. Herein, we introduced an electrochemical reaction into the thermochemical cycle and established a novel two-step water-splitting cycle based on LiFeO2/Fe redox pair. The two-step water-splitting process involves a cyclic operation of electrochemical reduction and water-splitting steps. The feasibility of the water-splitting cycle for the hydrogen production was thermodynamically and experimentally investigated. A mechanism of hydrogen production based on LiFeO2/Fe redox pair was developed. Compared with the traditional high-temperature thermochemical cycles, the electrochemical reduction and water-splitting steps of the process can be isothermally operated in the same cell at a relatively low temperature of 500 °C. The main advantages of the cycle are not only easily available heat sources without involvement of the associated engineering and materials issues, but also without any temperature swings. This is a promising method to achieve water splitting for hydrogen production in the future.