A novel electro-assisted thermochemical reactor for conversion of CO2/H2O into solar fuels

Solar-driven thermochemical conversion of CO2 and H2O into fuels via two-step redox cycles is considered as a significantly promising route for providing alternative energy. However, the current greatest challenge of such technology is the stringent requirement for high temperature and low oxygen partial pressure during the reduction step. To address this issue, this study proposes a novel electro-assisted thermochemical reactor for splitting of CO2 and H2O. In this design, an auxiliary voltage is introduced to enhance oxygen release during reduction step, namely, the reduction reaction is driven by both the chemical and electrical potentials. Such a dual-driven mode not only can relieve the heavy burden on reduction temperature and oxygen partial pressure, but also can retain original thermodynamic advantages. A comprehensive thermodynamic model of electro-assisted thermochemical redox cycle is established to demonstrate the reactor performance. Results indicate that when the auxiliary voltage E increases from 0.0 to 0.5 V, the Tred decreases from 1590 °C to 1140 °C, and pO2 increases from ∼10−6 bar to ∼10−1 bar, respectively, which is conducive to reducing heat losses and additional energy demand for oxygen removal as well as materials damage. Moreover, if the heat recovery is considered, the solar-to-fuel efficiency will be further improved and the theoretical maximum value can reach 37.89 % when 50 % of solid-phase sensible heat and 80 % of gas-phase sensible heat are supposed to be recovered. Therefore, this study provides a new path to push the development of solar-driven thermochemical fuel production toward a commercial scale.