4.1 Oxygen permeation membrane for H2O/CO2 splitting

Perovskites, ZrO2 and CeO2 (or doped ZrO2 and CeO2), usually constitute the selective oxygen permeation membrane utilized in high temperature (>600°C). Wang et al. [59] proposed a theoretical framework for the thermodynamic analysis of solar oxygen permeation membrane reactor, and the solar-to-fuel efficiency (ratio of the higher heating value of products to the total energy input) can reach as high as 89% in methane-assisted membrane reactor. Zhu et al. [60] brought up a thermodynamic model of ceria dense membrane for CO2 splitting, and the energy efficiency is above 10% at 1800 K without heat recovery. Steinfeld et al. [61, 62] have done a lot of experimental researches about solar CO2 splitting for CO generation by oxygen permeation membrane with 100% selectivity (e.g., La0.6Sr0.4Co0.2 Fe0.8O3-<sup>δ</sup> at 1030°C [61], CeO2 at 1600°C [62]), and Ozin [63] said the research of Steinfeld is an elegant demonstration and an exciting breakthrough for continuous CO2 splitting in a single step, at a single temperature, in a single reactor.
