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

The reverse water gas shift reaction (RWGS) represents an essential pathway for CO₂ 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 In₂O₃, CeO₂, ZrO₂, and Al₂O₃ were first evaluated to establish intrinsic reactivity and selectivity benchmarks. The single oxide CeO₂, In₂O₃, and ZrO₂ exhibited high RWGS activity with CO selectivity of 100%, while Al₂O₃ showed limited CO₂ conversion. Time-on-stream studies revealed that In₂O₃ undergoes progressive deactivation at 650 °C, whereas CeO₂ and ZrO₂ remain stable with CO₂ 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 In₂O₃ support and alkali of Na, K promoter for Al₂O₃. All binary systems preserved 100% CO selectivity. Among In₂O₃ based catalysts, 10% Mo/In₂O₃ demonstrated superior durability, maintaining stable CO₂ conversion above 60% for 48 h at 650 °C, attributed to optimized reducibility and moderated hydrogen interaction as evidenced by H₂-tempeature-programmed reduction. Calcination temperature also played a role for In₂O₃ and the calcined sample at 1100 °C showed enhanced structural stability compared to lower-temperature treated samples. For Al₂O₃ based catalysts, alkali promotion significantly increased CO₂ conversion by reducing strong acidity and enhancing surface basicity, with 5% K-Al₂O₃ approaching equilibrium conversion. X-ray Photoelectron Spectroscopy (XPS) analysis confirmed that deactivation of In₂O₃ is associated with progressive surface oxygen depletion and partial reduction, while Mo incorporation preserved lattice oxygen and Al₂O₃ 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.