Kinetic Control of Hexagonal Mg(OH)2 Nanoflakes for Catalytic Application of Preferential CO Oxidation

Abstract

Controlling the growth of nanocrystals is one of the most challenged issues in current catalytic field, which helps to further understand the size and morphology related behaviors for catalytic applications. In this work, we investigated the plane growth kinetics of Mg(OH)2 for catalytic application in preferential CO oxidation. Nanoflakes were synthesized through hydrothermal method. The morphology and structure of nanoflakes were characterized by TEM, SEM, and XRD. By varying the reaction temperature and time, Mg(OH)2 nanoflakes underwent an anisotropic growth. Benefited from the Ostwald ripening process, the thickness of nanoflake corresponding to the (110) plane of Mg(OH)2 was tuned from 7.6 nm to 24.0 nm, while the diameter of (001) plane increased from 18.2 nm to 30.2 nm. The grain growth kinetics for the thickness was well described in terms of an equation, D5 = 7.65 + 6.9 × 108exp(−28.14/RT). After depositing Pt nanoparticles onto these Mg(OH)2 nanoflakes, an excellent catalytic performance was achieved for preferential CO oxidation in H2-rich streams with a wide temperature window from 140 °C to 240 °C for complete CO conversion due to the interaction between Pt and hydroxyl groups. The findings reported here would be helpful in discovering novel catalysts for application of proton exchange membrane fuel cells.