Synthesizing active and durable cubic ceria catalysts (<6 nm) for fast dehydrogenation of bio-polyols to carboxylic acids coproducing green H2

Abstract

Dehydrogenation is considered as one of the most important industrial applications for renewable energy. Cubic ceria-based catalysts are known to display promising dehydrogenation performances in this area. Large particle size (>20 nm) and less surface defects, however, hinder further application of ceria materials. Herein, an alternative strategy involving lactic acid (LA) assisted hydrothermal method was developed to synthesize active, selective and durable cubic ceria of <6 nm for dehydrogenation reactions. Detailed studies of growth mechanism revealed that, the carboxyl and hydroxyl groups in LA molecule synergistically manipulate the morphological evolution of ceria precursors. Carboxyl groups determine the cubic shape and particle size, while hydroxyl groups promote compositional transformation of ceria precursors into CeO2 phases. Moreover, enhanced oxygen vacancies (Vö) on the surface of CeO2 were obtained owing to continuous removal of O species under reductive atmosphere. Cubic CeO2 catalysts synthesized by the LA-assisted method, immobilized with bimetallic PtCo clusters, exhibit a record high activity (TOF: 29,241 h−1) and Vö-dependent synergism for dehydrogenation of bio-derived polyols at 200 °C. We also found that quenching Vö defects at air atmosphere causes activity loss of PtCo/CeO2 catalysts. To regenerate Vö defects, a simple strategy was developed by irradiating deactivated catalysts using hernia lamp. The outcome of this work will provide new insights into manufacturing durable catalyst materials for aqueous phase dehydrogenation applications.

Keywords

• Cubic ceria
• Oxygen vacancy
• Dehydrogenation
• C–H bond activation