CO2 reduction with green H2 is an attractive way to produce fuels or chemicals. CO and CH4 are the main products for CO2 hydrogenation under atmospheric pressure while CH3OH and C2+ hydrocarbons/alcohols can be produced at high pressure. Unveiling the origin of tunable CO and CH4 selectivity is very important to rationally design CO2 hydrogenation catalysts as there are a lot of similarities between the atmospheric-pressure and high-pressure reactions in the reaction mechanism of CO2 hydrogenation. Here, a unique doping-segregation method based on Ni-based spinel is developed to precisely control the size of supported Ni nanoparticles from 1 nm to 12 nm, which strongly affects the product selectivity for CO2 hydrogenation reactions. Based on the in-situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) combined with transient response experiments, the reverse water-gas shift (RWGS) followed by H2-assisted CO dissociation and hydrogenation pathway is determined as the primary pathway for CO2 hydrogenation over Ni-based spinel catalysts. The activation energy of the rate-determining step (i.e., H2-assisted CO dissociation) and the activation temperature of CO in a hydrogen atmosphere are then identified as quantitative descriptors of CO2 hydrogenation selectivity. The generality of these descriptors is also demonstrated over various Ni-supported catalysts including Ni/SiO2, Ni/ZrO2, Ni/CeO2, and Ni/Al2O3. These results will guide the design of superior catalysts with a desired selectivity and bring new insight into Sabatier's principle for better understanding of the structure-performance relationship in heterogeneous catalysis.

Identifying quantitative descriptors of CH4 selectivity for CO2 hydrogenation over Ni-based spinel catalysts

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.