An Unprecedented CeO2/C Non-Noble Metal Electrocatalyst for Direct Ascorbic Acid Fuel Cells

Direct ascorbic acid fuel cells (DAAFCs) employ biocompatible ascorbic acid (AA) as fuel,allowing convenient storage, transportation, and fueling as well as avoiding fuel crossover. The AA oxidation reaction (AAOR) largely governs the performance of DAAFCs. However, AAORelectrocatalysts currently have low activity, and state-of-the-art ones are limited to carbon black.Herein, we report the synthesis of an unprecedented AAOR electrocatalyst comprising 3.9 +/- 1.1 nmCeO(2) nanoparticles evenly distributed on carbon black simply by the wet chemical precipitationof Ce(OH)3and a subsequent heat treatment. The resultant CeO2/C shows a remarkable AAORactivity with a peak current density of 13.1 mA cm(-2), which is 1.7 times of that of carbon black(7.67 mA cm(-2)). According to X-ray photoelectron spectroscopy (XPS), the surface Ce(3+)of CeO2appears to contribute to the AAOR activity. Furthermore, our density functional theory (DFT)calculation reveals that that the proton of the hydroxyl group of AA can easily migrate to the bridgingO sites of CeO2, resulting in a faster AAOR with respect to the pristine carbon, -COOH, and -C=O sitesof carbon. After an i-t test, CeO2/C loses 17.8% of its initial current density, which is much superiorto that of carbon black. CeO(2)can capture the electrons generated by the AAOR to protect the -COOH and -C=O sites from being reduced. Finally, DAAFCs fabricated with CeO2/C exhibit a remarkablepower density of 41.3 mW cm-2, which is the highest among proton-exchange-membrane-basedDAAFCs in the literature

Automated summary

In this study, we report the synthesis of a novel electrocatalyst for the ascorbic acid oxidation reaction (AAOR) in direct ascorbic acid fuel cells (DAAFCs). The CeO2 nanoparticles evenly distributed on carbon black show remarkable AAOR activity, attributed to the surface Ce3+ of CeO2. Additionally, CeO2/C can capture the electrons generated by AAOR, protecting the -COOH and -C=O sites from being reduced. The DAAFCs fabricated with CeO2/C exhibit a remarkable power density.