Charge polarization-modulated Pd-Ni(OH)2 hybrids in mesoporous silica SBA-15 for efficient low-temperature CO2 hydrogenation to formate

Abstract

Converting CO2 to formic acid/formate is a considerably significant pathway for future energy storage and utilization; however, it is critical to tailor high-performance catalysts for realizing the process. Herein, highly dispersed Pd-Ni(OH)2 hybrids were immobilized in ordered mesoporous silica SBA-15 via a facile impregnation method. The prepared SBA-15-supported Pd-Ni(OH)2 catalyst exhibited extraordinarily high catalytic performance and stability during the hydrogenation of CO2 toward formate. Significantly, Pd5Ni5/SBA-15, an optimized Pd5Ni5/SBA-15 catalyst afforded a superior formate generation rate of 150.5 molformate moltotalPd-1h−1 at a low temperature (40 °C), which was about 3-fold higher than that of monometallic Pd counterpart. Such a catalytic activity outperforms most of the previously reported catalysts because of its charge polarization action and synergy between bimetallic components as well as ultrasmall and well-dispersed metal species with increased accessible active sites. The relevant experimental observations were well supported by density functional theory (DFT) calculations. In addition, the catalytic activity of SBA-15-supported metal catalysts remained unchanged even after the 5th cycle, demonstrating excellent cycling durability due to the confinement effect of mesoporous silica. The facile synthesis strategy and excellent catalytic performance hold great potential applications of the prepared catalysts in CO2 hydrogenation to formate.