Highly Active and Stable Ni/La-Doped Ceria Material for Catalytic CO 2 Reduction by Reverse Water-Gas Shift Reaction.

The design of an active, effective, and economically viable catalyst for CO ₂ conversion into value-added products is crucial in the fight against global warming and energy demand. We have developed very efficient catalysts for reverse water-gas shift (rWGS) reaction. Specific conditions of the synthesis by combustion allow the obtention of macroporous materials based on nanosized Ni particles supported on a mixed oxide of high purity and crystallinity. Here, we show that Ni/La-doped CeO ₂ catalysts─with the "right" Ni and La proportions─have an unprecedented catalytic performance per unit mass of catalyst for the rWGS reaction as the first step toward CO ₂ valorization. Correlations between physicochemical properties and catalytic activity, obtained using a combination of different techniques such as X-ray and neutron powder diffraction, Raman spectroscopy, in situ near ambient pressure X-ray photoelectron spectroscopy, electron microscopy, and catalytic testing, point out to optimum values for the Ni loading and the La proportion. Density functional theory calculations of elementary steps of the reaction on model Ni/ceria catalysts aid toward the microscopic understanding of the nature of the active sites. This finding offers a fundamental basis for developing economical catalysts that can be effectively used for CO ₂ reduction with hydrogen. A catalyst based on Ni _0.07 /(Ce _0.9 La _0.1 O _x ) _0.93 shows a CO production of 58 × 10 ^-5 mol _CO ·g _cat ^-1 ·s ^-1 (700 °C, H ₂ /CO ₂ = 2; selectivity to CO > 99.5), being stable for 100 h under continuous reaction.