Single-Atom Molybdenum-N Sites for Selective Hydrogenation of CO to CO.

The design of efficient non-noble metal catalysts for CO hydrogenation to fuels and chemicals is desired yet remains a challenge. Herein, we report that single Mo atoms with a MoN (pyrrolic) moiety enable remarkable CO adsorption and hydrogenation to CO, as predicted by density functional theory studies and evidenced by a high and stable conversion of CO reaching about 30.4 % with a CO selectivity of almost 100 % at 500 °C and very low H partial pressure. Atomically dispersed MoN is calculated to facilitate CO activation and reduces CO to CO* via the direct dissociation path. Furthermore, the highest transition state energy in CO formation is 0.82 eV, which is substantially lower than that of CH formation (2.16 eV) and accounts for the dominant yield of CO. The enhanced catalytic performances of Mo/NC originate from facile CO desorption with the help of dispersed Mo on nitrogen-doped carbon (Mo/NC), and in the absence of Mo nanoparticles. The resulting catalyst preserves good stability without degradation of CO conversion rate even after 68 hours of continuous reaction. This finding provides a promising route for the construction of highly active, selective, and robust single-atom non-precious metal catalysts for reverse water-gas shift reaction.