In this study, we investigate the effects of adding titanium dioxide (TiO2) and samarium doped cerium oxide (SDC) on the properties of yttrium-stabilized zirconia (YSZ) electrolyte. The microstructure, mechanical, and electrochemical properties of the electrolyte are investigated. The performance in CO2 electrolysis is measured by supplying carbon dioxide to Ni-YSZ electrode and nitrogen to LSM electrode. Results show that TiO2 and SDC addition can reduce the sintering temperature and increase grain size. The ionic conductivity is 0.123 S cm−1 at 1000 °C. In addition, the thermal expansion coefficient at 1000 °C is 8.25 × 10−6 K−1. The current density of the cell is 439 mA cm−2 at 1.3 V and 1000 °C in solid oxide electrolysis cell.