Perovskite materials for hydrogen production by thermochemical water splitting

Abstract

The performance of perovskites as redox materials for solar thermochemical hydrogen production and energy storage have been studied theoretically by several authors but there are only a few experimental studies about them. In this work, an evaluation of commercial perovskite materials La1−xSrxMeO3 (Me = Mn, Co and Fe) for thermochemical water splitting is presented. The studied perovskites showed suitable redox properties for energy storage in thermogravimetric analysis (TGA) in presence of air, although only the Co-perovskite material (LSC) exhibited cyclability capacity. Experiments of thermochemical water splitting revealed hydrogen production, with increasing yields for Mn-, Fe- and Co-substituted perovskites, respectively. La/Sr ratio in the range of x = 0.2 to 0.4 showed only a slight influence on the amount of hydrogen produced and on the temperature required for the processes. On the other hand, metal substitution type seems to be a critical factor for the thermal reduction of these perovskites, taking place at temperatures above 1000 °C for the Mn-perovskite, 800 °C for Co-material and 900 °C for Fe-material. These results experimentally demonstrate the suitability of solar hydrogen production based on La1−xSrxMeO3 thermochemical cycles. Moreover, the required temperatures for hydrogen production (230 °C) are lower than those commonly reported in literature for “pure” MenOy oxide cycles (500 °C), making perovskite-based cycles a promising alternative. The cyclability studies with the LSC showed a slight decrease in the hydrogen production, derived from the segregation of metallic Co during the thermochemical cycle. This study confirmed the LSC perovskite as a promising material for hydrogen production by solar-driven thermochemical water splitting, although a further insight in the optimization of the operation under consecutive cycles is necessary in order to assess the material as alternative as redox material for a full-scale application.