Reactivity Support for RWGS reaction for maximize CO selectivity and CO2 conversion

The reverse water gas shift reaction (RWGS) represents an essential pathway for CO 2 valorization into CO as a multipurpose intermediate feed for sustainable fuels and chemicals. In this study, the influencing factors on activity of reactive supports of single oxide and binary oxide catalyst were investigated. Metal oxide supports of In 2 O 3 , CeO 2 , ZrO 2 , and Al 2 O 3 were first evaluated to establish intrinsic reactivity and selectivity benchmarks. The single oxide CeO 2 , In 2 O 3 , and ZrO 2 exhibited high RWGS activity with CO selectivity of 100%, while Al 2 O 3 showed limited CO 2 conversion. Time-on-stream studies revealed that In 2 O 3 undergoes progressive deactivation at 650 °C, whereas CeO 2 and ZrO 2 remain stable with CO 2 conversion above 60%. To enhance stability and tailor surface properties, binary oxide catalysts were developed via transition metals of Mo, Cu, Zn, and Ni modification to In 2 O 3 support and alkali of Na, K promoter for Al 2 O 3 . All binary systems preserved 100% CO selectivity. Among In 2 O 3 based catalysts, 10% Mo/In 2 O 3 demonstrated superior durability, maintaining stable CO 2 conversion above 60% for 48 h at 650 °C, attributed to optimized reducibility and moderated hydrogen interaction as evidenced by H 2 -tempeature-programmed reduction. Calcination temperature also played a role for In 2 O 3 and the calcined sample at 1100 °C showed enhanced structural stability compared to lower-temperature treated samples. For Al 2 O 3 based catalysts, alkali promotion significantly increased CO 2 conversion by reducing strong acidity and enhancing surface basicity, with 5% K-Al 2 O 3 approaching equilibrium conversion. X-ray Photoelectron Spectroscopy (XPS) analysis confirmed that deactivation of In 2 O 3 is associated with progressive surface oxygen depletion and partial reduction, while Mo incorporation preserved lattice oxygen and Al 2 O 3 maintained complete surface stability. Overall, catalytic performance in RWGS is governed by a balance between redox behavior, acid–base properties, and structural robustness, providing rational design principles for stable and selective oxide-based catalysts.