Modulating Pt States through Hydroxyl Control for Low-Temperature Aqueous Phase Reforming of Methanol

Abstract

Aqueous phase reforming of methanol (APRM) offers a method for releasing H₂ from the liquid phase, by which H₂ can be stored in methanol safely. It is an efficient way to design high-performance catalysts by controlling the hydroxyl (OH) groups, but its mechanism for affecting the APRM is still unclear. Herein, we loaded Pt on three types of Al₂O₃ (nanopolyhedron, nanosheet, and nanorod Al₂O₃) with different OH contents and types. Among them, Pt/nanorod Al₂O₃ exhibited the highest H₂ production rate of 20.4 μmol g^–1 s^–1 with 96.6% H₂ selectivity at a low temperature of 190 °C. This was attributed to the roles of hydroxyl groups in modulating Pt states. On nanopolyhedron, nanosheet, and nanorod Al₂O₃, the bonding of Pt with O atoms became more favorable as the dehydroxylation happened. In particular, on nanorod Al₂O₃, the dehydroxylation process generated a high density of five-coordinated Al (Al_V) sites, facilitating the dispersion and anchoring of Pt particles. Moreover, the special OH groups (hydrogen bond donor) on nanorod Al₂O₃ promoted Pt particle reduction via the movement of electrons. Ultimately, the results demonstrated the influence of OH groups on the dispersion and reduction of active metals, offering perspectives for designing catalysts for APRM through hydroxyl control.