Valorization of carbon dioxide into C1 product via reverse water gas shift reaction using oxide-supported molybdenum carbides
Andrew N. Kuhn, Rachel C. Park, Siying Yu, Di Gao, Cheng Zhang, Yuanhui Zhang, Hong Yang
Abstract
Conversion of carbon dioxide (CO<sub>2</sub>) to C1 products such as carbon monoxide (CO) is a critical step towards carbon valorization.<strong> </strong>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-Mo<sub>2</sub>C) and platinum-group metals make them promising alternatives to traditional catalysts. In this work, we studied the effect of oxide supports (MO<em><sub>x</sub></em>, M = Al, Ce, Mg, Si, and Ti) on the formation and catalytic properties of β-Mo<sub>2</sub>C nanoparticle catalysts. The β-Mo<sub>2</sub>C/SiO<sub>2</sub> catalyst exhibited a mass activity of 372 μmol<sub>CO</sub><sub>2 </sub>g<sup>-1</sup><sub>Mo</sub><sub>2C</sub> s<sup>-1 </sup>at 400 °C and 1109 μmol<sub>CO</sub><sub>2 </sub>g<sup>-1</sup><sub>Mo</sub><sub>2C</sub> s<sup>-1</sup> at 600 °C for the conversion of CO<sub>2</sub>. The β-Mo<sub>2</sub>C/SiO<sub>2</sub> 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 SiO<sub>2</sub> and the low H<sub>2</sub>:CO<sub>2</sub> 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 CO<sub>2</sub>.