Hydroxyl-rich ceria hydrate nanoparticles enhancing the alcohol electrooxidation performance of Pt catalysts

Abstract

The exploration of anode catalysts with high activity and stability for direct alcohol fuel cells (DAFCs) has been a big challenge for decades. Metal oxides, such as CeO₂ with oxygen vacancies, are widely investigated in the promotion of Pt-based electrocatalysts for alcohol oxidation. Hydroxyl-rich CeO₂·xH₂O, which is capable of affording OH groups directly for reacting with CO to re-activate the nearby metal catalyst, may surpass CeO₂ in alcohol electrooxidation reactions. Herein, small CeO₂·xH₂O nanoparticles with plenty of surface OH groups have been prepared by a tert-butylamine-assisted solvothermal method, and then ultrasonically mixed with Pt/CNTs (CNTs = carbon nanotubes). As a proof-of-concept experiment, the CeO₂·xH₂O/Pt/CNT catalyst containing the tert-butylamine-modified CeO₂·xH₂O nanoparticles achieves a high peak current density of 2304 mA mg⁻¹ for methanol oxidation in the alkaline medium, which is remarkably higher than those of the calcined counterpart (CeO₂/Pt/CNTs, 814 mA mg⁻¹) and Pt/CNTs (520 mA mg⁻¹). After a chronoamperometry test for 1200 s, the retained current density of CeO₂·xH₂O/Pt/CNTs (570 mA mg⁻¹) is also much higher than those of CeO₂/Pt/CNTs (163 mA mg⁻¹) and Pt/CNTs (10 mA mg⁻¹). The advantage of CeO₂·xH₂O nanoparticles over CeO₂ nanoparticles has been further confirmed by ethylene glycol and glycerol oxidation reactions, and they have also been found to be effective over other alcohol oxidation catalysts such as Pt/C, Pd/C and PtRu/C. Therefore, this strategy may provide an alternative for the design of anode catalysts in DAFCs with high performance and low cost.