Valorization of carbon dioxide into C1 product via reverse water gas shift reaction using oxide-supported molybdenum carbides

Conversion of carbon dioxide (CO₂) to C1 products such as carbon monoxide (CO) is a critical step towards carbon valorization. The conversion has been largely carried out through the reverse water gas shift (RWGS) reaction using noble metal catalysts or copper-based nanostructures. Similarities in the electronic structures between beta phase molybdenum carbides (β-Mo₂C) and platinum-group metals make them promising alternatives to traditional catalysts. In this work, we studied the effect of oxide supports (MO_x, M = Al, Ce, Mg, Si, and Ti) on the formation and catalytic properties of β-Mo₂C nanoparticle catalysts. The β-Mo₂C/SiO₂ catalyst exhibited a mass activity of 372 μmol_CO2∙ ${\mathrm{g}}_{\mathrm{M}{\mathrm{o}}_2\mathrm{C}}^{-1}$∙s⁻¹ at 400 °C and 1109 μmol_CO2∙ ${\mathrm{g}}_{\mathrm{M}{\mathrm{o}}_2\mathrm{C}}^{-1}$∙s⁻¹ at 600 °C for the conversion of CO₂. The β-Mo₂C/SiO₂ catalysts also maintained selectivity and showed structural stability in the on-stream study. The enhanced catalytic performance could be attributed to the size of nanocatalysts (4.7 nm), whereas the stability is related to the interaction with SiO₂ and the low H₂:CO₂ feed ratio. This work highlights the application of amorphous silica in preparing metal carbide nanocatalysts. The rich defects and surface vacancies in the silica support greatly facilitate the high-rate and highly selective processes towards the valorization of CO₂.