Volcano Trend between the Size of Ru Nanocatalysts and Hydrogenation Activity for Levulinic Acid

Regulating the size of the active metal is crucial to change the electronic structure and catalytic activity. Here, five Ru/CN-ZrO 2 catalysts with different sizes are precisely constructed via a two-step wet chemical synthesis method. Remarkably, a volcano trend between the size of Ru and hydrogenation activity for levulinic acid (LA) is disclosed. The Ru nanoclusters with an average size of ∼2.7 nm (Ru/CN-ZrO 2 -2) exhibit the highest catalytic activity for LA hydrogenation, achieving an LA conversion of 99.4% and a γ-valerolactone (GVL) selectivity of 99.3%. Besides, the corresponding turnover frequency (TOF) is 4860.1 h –1 , which far surpasses that most reported for Ru-based catalysts. Mechanism studies reveal Ru/CN-ZrO 2 -2 with moderate size is beneficial to enhance the interaction between Ru and support, directly promoting the adsorption of LA, and thereby exhibiting the lowest activation energy. This work emphasizes the size effect to improve the catalytic activity, which is an important guidance for the rational design of hydrogenation catalysts.