Solar CO2 splitting coupling with PV, photon-enhanced thermionic emission cell and SOEC for efficient full-spectrum utilization in a wide temperature range

CO2 splitting driven by solar energy is a clean and promising approach for addressing the issue of CO2 emission and approaching the dual‑carbon target. Here, a high-efficient solar CO2 electrolysis system containing photovoltaic (PV) cell, photon-enhanced thermionic emission (PETE) cell, and solid oxide electrolysis cell (SOEC) is proposed. CO2 serves as cooling fluid to decrease the temperature of PV cells for the enhancement of PV efficiency, and the heated CO2 by PV cells and PETE cells is fed into SOEC at a high temperature to decrease the Gibbs free energy utilized in electrolysis. The combination of PV cells and PETE cells can enlarge the temperature range from room temperature to the working temperature of SOEC for full solar spectrum utilization. Compared to H2O splitting in SOEC, CO2 splitting can convert more thermal energy with relatively low energy level into high-energy-level chemical energy. The system can reach the energy efficiency, exergy efficiency, and solar-to-fuel efficiency of 73.5%, 48.0%, and 33.3%, respectively. This research sheds light on high-efficient solar CO2 splitting system design with full solar spectrum utilization in a wide temperature range.