CO₂ Hydrogenation to Methanol over In₂O₃: The Size Effect

Indium oxide (In2O3) and In2O3-supported catalysts for CO2 hydrogenation to methanol have attracted increasing interest because of their high methanol selectivity, even at elevated temperatures. However, the stability behavior of In2O3 is still not clear. In this work, the size effect of In2O3 on activity and stability has been investigated. It was found that the smaller In2O3 nanoparticle possesses more surface oxygen vacancies as active sites for CO2 activation and H2 dissociation. Higher initial activity is achieved. However, the smaller In2O3 nanoparticle is prone to be over-reduced during the reaction, causing a deactivation of In2O3. On the contrary, the larger In2O3 nanoparticle has a lower initial activity but effectively prevents the over-reduction. The larger particle size helps the stabilization of surface oxygen vacancies and enhances the stability of In2O3 for the hydrogenation of CO2 to methanol. The present study of the size effect is important for the improvement in the stability of the In2O3 catalyst by either metal loading (to form the In2O3-supported catalyst) or the formation of In2O3–ZrO2 solid solution