Origin of Autocatalytic Behavior of Water over CuZn Alloy in CO Hydrogenation.

Water plays a significant role in CO hydrogenation, which is capable of accelerating the reaction in an autocatalytic manner, but the reason for water promotion in the system is still controversial. This work dissects the mechanisms behind the autocatalytic behavior of water in CO hydrogenation. Based on the stable structure of CuZn(211) alloy under the reaction condition, density functional theory is employed to systematically explore all possible autocatalytic modes of water. We find that the influence of water on the reaction is mainly reflected in O-H bonding, in which water tends to facilitate the O-H bond formation by a direct participator mechanism. The nature of the facilitating effect is attributed to the nucleophilic property of O-H bonding. Due to the involvement of water, the reaction activity is enhanced with the improvement of CO selectivity. This work can provide a paradigm for investigating the origin of the autocatalytic behavior of water in heterogeneous catalysis.