High-entropy (CoCrFeMnNi)3O4 catalysts for propane catalytic destruction: Effect of the precipitation agent

Efficient catalytic destruction of light alkane with ultra-stable and highly symmetric structure is still an intractable issue. High entropy oxides (HEOs) with high chemical disorder and lattice distortion and superior stability have shown great potential in heterogeneous thermocatalysis. Herein, spinel-type HEOs are synthesized via a scalable co-precipitation method with different precipitants (NaOH, Na2CO3, and NaHCO3) and firstly adopted in catalytic destruction of propane. Results demonstrate that the HEO-NaOH possesses the best activity, achieving 90% of propane conversion at 325 °C with an apparent activation energy of 56 kJ mol−1. Compared with other two HEOs, the HEO-NaOH has larger quantities of surface oxygen vacancies and easily forms several reactive oxygen species (OOH−, O2−, and OH−, etc.), which significantly contribute to improve the catalytic performance. Moreover, the excellent water resistance of HEOs is verified due to their high conformational entropy and structural stability. Reaction mechanism reveals that OOH− and O2− are the key species in the oxidation of C3H8, which break C-H and C-C bonds in sequence, and are then converted to oxygenated compounds via oxygen oxidation before the final mineralization. The present work provides new insights into the fabrication of efficient catalysts for light alkane destruction as well as other thermocatalytic applications.