Bottom-up synthesis of cerium–citric acid coordination polymers hollow microspheres with tunable shell thickness and their corresponding porous CeO2 hollow spheres for Pt-based electrocatalysts

Abstract

Dispersed cerium based CPs hollow microspheres derived from the “green” ligand–citric acid were fabricated for the first time via a bottom-up and template-free way under hydrothermal conditions. The shell thickness of hollow spheres could be facially tuned by changing the reaction time, and the morphology could also be regulated by tuning the pH values and molar ratios of reactants. The formation mechanism of hollow microspheres was demonstrated as an Ostwald ripening process, and the release of H₂Cit⁻ was proposed as the promotion of the hollowing process. Moreover, with the CPs hollow spheres as precursors, corresponding porous CeO₂ hollow spheres were obtained, and after loading with Pt, the Pt/CeO₂ electrodes displayed a relatively high current density and I_f/I_b value for electrocatalysis of methanol.