Mechanism of sulfur-guided CO2 selective hydrogenation through modulation of surface intermediate over Ni/ZrO2 catalysts

Abstract

Regulating the selectivity between CO and CH4 during CO2 hydrogenation is a challenging research topic. Going beyond the traditional framework of adjusting the adsorption strength of CO*, in this work, a sulfur (S)-guided selective method based on the regulation of key intermediate H3CO* was introduced. With S assistance, the selectivity of CO2 hydrogenation shifted from over 80 % CH4 for Ni/ZrO2 to about 100 % CO for Ni/ZrO2-S. S modification weakened the H2 adsorption/dissociation/spillover abilities and hydrogenation capacity of the surface Ni by inducing an electron-deficient state. S modification also enhanced the adsorption strength of intermediate H3CO* by accumulating electrons in its bonding region. The aforementioned synergistic effect increased the energy barrier of H3CO* hydrogenation to 0.55 eV (7.9 times higher than without S), suppressing CH4 formation and favoring CO generation via formate decomposition. This work opens a new and universal avenue for selectively controlling CH4 or CO production in CO2 hydrogenation.