The Co-In2O3 interaction concerning the effect of amorphous Co metal on CO2 hydrogenation to methanol

Hydrogenation of CO 2 to valuable chemicals has the potential to mitigate the elevated CO 2 level and depletion of fossil fuel problems. Herein, bamboo powder (BP) assisted synthesis of Co 3 O 4 -In 2 O 3 catalysts was applied for efficient CO 2 hydrogenation to methanol (MeOH). Under reaction stabilization, Co 3 O 4 in BP-modified catalyst has a stronger interaction with In 2 O 3 , and will be transformed into amorphous Co 0 and inactive Co 3 InC 0.75 (the weight fraction of Co 3 InC 0.75 in the catalyst is 69 wt%). In contrast, without assistance of BP, crystalline Co 0 is formed and the mass content of Co 3 InC 0.75 also reaches 61 wt%. Density function theory calculation gives the information that H 2 molecules are more easily adsorbed and dissociated on amorphous Co 0 compared to crystalline Co 0 , which further facilitates the oxygen vacancy formation of In 2 O 3 . On the other hand, in situ DRIFTs confirms that MeOH synthesis over the Co 3 O 4 -In 2 O 3 catalyst follows the dual-site model. That is, active Co 0 and oxygen vacancies are both important, in which the former is associated with H 2 dissociation while the latter is closely relatively to CO 2 activation. Besides, K + species originated from BP in BP-modified catalyst favor CO production, and the negative role can be eliminated by an easy HCl washing. As a result, at the sacrification of some decreased Co 0 but with higher reactive amorphous Co 0 , BP-1-mediated biosynthesis of Co 3 O 4 -In 2 O 3 (BP treated in pH = 1) attains a better MeOH space-time yield of 13.39 mmol g cat −1 h −1 at 300 °C and 4 MPa. Moreover, the above catalyst shows excellent stability with almost no deactivation in a continuous run of 100 h. • With the help of BP, amorphous Co 0 was formed during reaction reconstruction. • Amorphous Co 0 has stronger interaction with In 2 O 3 than crystalline Co 0 . • H 2 molecules are more easily adsorbed and dissociated on amorphous Co 0 . • A methanol space-time yield of 13.39 mmol g cat −1 h −1 was reached over Co-In oxide at 300 °C and 4 MPa.