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, AAOR electrocatalysts 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 nm CeO2 nanoparticles evenly distributed on carbon black simply by the wet chemical precipitation of Ce(OH)3 and a subsequent heat treatment. The resultant CeO2/C shows a remarkable AAOR activity 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 Ce3+ of CeO2 appears 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 bridging O sites of CeO2, resulting in a faster AAOR with respect to the pristine carbon, -COOH, and -C=O sites of carbon. After an i-t test, CeO2/C loses 17.8% of its initial current density, which is much superior to that of carbon black. CeO2 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 remarkable power density of 41.3 mW cm-2, which is the highest among proton-exchange-membrane-based DAAFCs in the literature.

In situ Preparation of HNbMoO6/C Nanocomposite for Sensitive Detection of Clenbuterol

In this paper, we synthesized HNbMoO₆/C composite through the calcination of octylamine-intercalated HNbMoO₆ precursor. The resulting HNbMoO₆/C composite showed some new phases of MoO₂, MoO₃, NbO₂, Nb₂O₅, and carbon, which was fully confirmed via powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) technologies. Besides, the HNbMoO₆/C hybrid was coated on glass carbon electrode to construct an electrochemical sensor for sensitive determination of clenbuterol. The electrochemical behaviors of clenbuterol on the prepared electrode were tested by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) analysis. The results showed that the intercalated carbon can act as active sites to accelerate electron transfer. In addition, more exposed surface areas of the HNbMoO₆/C composite will facilitate the electrolyte to permeate. The oxidation peak current of clenbuterol was linearly related to its concentration in the range of 1.04 × 10^-5 to 7.51 × 10^-4 mol L^-1, and the determination limit was calculated to be 3.03 × 10^-6 mol L^-1 (S/N = 3). This sensor exhibits excellent stability, reproducibility, specificity, and good recoveries when applied to monitor clenbuterol in real samples.