Adjacent Reaction Sites of Atomic Mn2O3 and Oxygen Vacancies Facilitate CO2 Activation for Enhanced CH4 Production on TiO2-Supported Nickel-Hydroxide Nanoparticles

The catalytic conversion of carbon dioxide (CO2) to methane (CH4) through the “Sabatier
reaction”, also known as CO2 methanation, presents a promising avenue for establishing a closed
carbon loop. However, the competitive reverse water gas shift (RWGS) reaction severely limits
CH4 production at lower temperatures; therefore, developing highly efficient and selective catalysts
for CO2 methanation is imperative. In this regard, we have developed a novel nanocatalyst comprising
atomic scale Mn2O3 species decorated in the defect sites of TiO2-supported Ni-hydroxide
nanoparticles with abundant oxygen vacancies (hereafter denoted as NiMn-1). The as-prepared
NiMn-1 catalyst initiates the CO2 methanation at a temperature of 523 K and delivers an optimal
CH4 production yield of 21,312 mmol g−1 h−1 with a CH4 selectivity as high as ~92% at 573 K, which
is 45% higher as compared to its monometallic counterpart Ni-TiO2 (14,741 mmol g−1 h−1). Physical
investigations combined with gas chromatography analysis corroborate that the exceptional activity
and selectivity of the NiMn-1 catalyst stem from the synergistic cooperation between adjacent active
sites on its surface. Specifically, the high density of oxygen vacancies in Ni-hydroxide and adjacent
Mn2O3 domains facilitate CO2 activation, while the metallic Ni domains trigger H2 splitting. We
envision that the obtained results pave the way for the design of highly active and selective catalysts
for CO2 methanation.