Experimental demonstration of vanadium-doped nanostructured ceria for enhanced solar thermochemical syngas production

Solar-driven thermochemical routes enable storage of solar energy in chemical form for off-sun use by means of synthetic fuel production. Here, we explore vanadium-doped ceria materials for partial oxidation of methane, followed by an efficient splitting of CO₂ and H₂O into syngas. The primary role of the dopant is to enhance and optimize the cycle capacity of ceria at low isothermal temperatures. The intake capacity of ceria lattice reached its saturation level with 5% of vanadium addition and further increase in V (%) forms a secondary phase (CeVO₄), which significantly affects the role of vanadium towards the syngas production performance enhancement. For instance, vanadium atoms migrate to the powder surface with V ≥ 5% and cause cracking of methane, while the lattice vanadium atoms (V < 5%) enhances the cycle capacity by providing reducing sites for the redox reactions and improve the oxygen mobility by inducing lattice distortions. The cycle capacity of V-doped ceria is four times higher than pure ceria, while the temperature for the methane partial oxidation reaction is decreased by up to 178 °C with elevated peak syngas production rates, after vanadium doping. The long-term redox activity of V-doped ceria materials for 200 cycles with up to 4.5 mmol g⁻¹/cycle of syngas is reported. This study demonstrates the concept of utilizing V-doped ceria to produce syngas via high temperature chemical looping reforming of methane and helps to strategically evaluate the redox materials as an efficient oxygen carrier for syngas production.