Decoupling the effect of Ni particle size and surface oxygen deficiencies in CO2 methanation over ceria supported Ni

The study describes decoupling the effect of surface oxygen vacancies and Ni particle size in the CO2 methanation over CeO2 supported Ni nanoparticles. The availability of surface oxygen vacancies with the interaction between Ni and CeO2 served to appreciably enhance the catalytic capacity for activation of CO2, generating higher conversion rates, larger selectivity to CH4 and lower activation energies relative to Ni/SiO2. A structure-sensitivity in the reaction over Ni/CeO2 was established without the interference of different concentrations of surface oxygen vacancies, where the turnover frequencies of CO2 decreased with increasing the Ni nano-particle sizes (8-21 nm). The TPSR and Operando FT-IR analysis demonstrated that formate was the critical intermediate for CH 4 formation. The CO formation with smaller nickel size resulted from the carboxyl species. In addition, the long-term evaluations and TGA measurements revealed small Ni nanoparticles suffered a temporary loss of activity due to the carbon deposition.

Automated summary

This study investigates the effect of surface oxygen vacancies and Ni particle size in the CO2 methanation over CeO2 supported Ni nanoparticles. Results show that surface oxygen vacancies significantly enhance the catalytic capacity, while the reaction over Ni/CeO2 exhibits structure-sensitivity to Ni nano-particle sizes and formate is identified as the critical intermediate for CH4 formation. Additionally, long-term evaluations reveal temporary activity loss in small Ni nanoparticles due to carbon deposition.