Low-temperature catalytic chemical looping dry reforming of methane over Ru/La₂Ce₂O₇

Chemical looping dry reforming of CH4, a promising approach to reduce fossil fuel consumption and use CO2, hinges on designing an efficient oxygen carrier. However, high operating temperatures and unsatisfactory performance hamper its application. Loading a small amount of Ru promoter on the La2Ce2O7 oxygen carrier enhances CH4 activation considerably, lowering the onset temperature to around 545 K. The Ru/La2Ce2O7 material exhibited impressive performance, achieving CH4 conversion of around 65%, with almost negligible CO2 produced during the reduction step and CO2 conversion exceeding 95% during the CO2 re-oxidation step over 10 redox cycles. Despite slight carbon deposition, the redox performance remains stable because of efficient carbon removal in the reoxidation step and the inherent structure stability of the oxygen carrier. This superior performance is attributed to the strong metal-support interaction between Ru and La2Ce2O7, forming Ru-O-Ce bonds at the Ru delta+-CeO2-x interface. These bonds anchor active Ru onto stable La2Ce2O7 with excellent oxygen-ionic conductivity, enhancing CH4 activation by increasing surface oxygen vacancies and maintaining structural stability with well-dispersed Ru promoters during cycles. Moreover, the migration of O2- in subsurface is promoted by creating an elevated oxygen chemical potential gradient induced by the oxygen-deprived surface, facilitated by the Ru promoter.