RESUMEN
The oxygen reduction reaction (ORR) is a key energy conversion process, which is critical for the efficient operation of fuel cells and metal-air batteries. Here, we report the significant enhancement of the ORR-performance of commercial platinum-on-carbon electrocatalysts when operated in aqueous electrolyte solutions (pHâ 5.6), containing the polyoxoanion [Fe28 (µ3 -O)8 (L-(-)-tart)16 (CH3 COO)24 ]20- . Mechanistic studies provide initial insights into the performance-improving role of the iron oxide cluster during ORR. Technological deployment of the system is demonstrated by incorporation into a direct formate microfluidic fuel cell (DFMFC), where major performance increases are observed when compared with reference electrolytes. The study provides the first examples of iron oxide clusters in electrochemical energy conversion and storage.
RESUMEN
The preparation of low-loading and high-performance Pd-based electrodes is required for direct formate fuel cells. In this study, cyclic voltammetry electrodeposition is used to electrodeposit Pd nanoparticles on carbon paper (Pd/CP) and achieve excellent activity and promising stability toward the formate oxidation reaction (FOR). The prepared electrode shows a thin layer of hemispherical and well-dispersed Pd nanoparticles on the fibers of the carbon paper. The open structure and uniform catalyst distribution make the Pd/CP electrode show 2.56-fold higher active area and stability in the FOR as compared with those of commercial Pd/C catalysts. An air-breathing microfluidic direct formate fuel cell (µDFFC) with a Pd/CP electrode used as a flow-through anode is constructed to further assess electrode performance. The Pd/CP electrode with low Pd loading, 0.105 mg cm-2, delivers a peak power density and limiting current density of 46.6 mW cm-2 (443.8 mW mg-1Pd) and 288.4 mA cm-2, respectively. The performance of the µDFFC is superior to those of most others reported in the literature, further boosting the commercialization of this direct formate fuel cell to power next-generation portable electronics.
RESUMEN
A 3-D macroporous anode was constructed using different numbers of graphite rod arrays in fixed-volume bio-electrochemical systems (BESs), and the current and biofilm distribution were investigated by dividing the 3-D anode into several subunits. In the fixed-volume chamber, current production was not significantly improved after the electrode number increased to 36. In the case of 100 electrodes, a significant uneven current distribution was found in the macroporous anode. This was attributed to a differential pH distribution, which resulted from proton accumulation inside the macroporous anode. The pH distribution influenced the biofilm development and led to an uneven biofilm distribution. With respect to current generation, the uneven distribution of both the pH and biofilm contributed to the uneven current distribution. The center had a low pH, which led to less biofilm and a lower contribution to the total current, limiting the performance of the BESs.
Asunto(s)
Fuentes de Energía Bioeléctrica/microbiología , Grafito , Biopelículas , Electrodos , Diseño de Equipo , Concentración de Iones de Hidrógeno , PorosidadRESUMEN
Two identical microbial fuel cells (MFCs) with a floating air-cathode were operated under either buffered (MFC-B) or bufferless (MFC-BL) conditions to investigate anolyte recirculation effects on enhancing proton transfer. With an external resistance of 50 Ω and recirculation rate of 1.0 ml/min, MFC-BL had a 27% lower voltage (9.7% lower maximal power density) but a 64% higher Coulombic efficiency (CE) than MFC-B. MFC-B had a decreased voltage output, batch time, and CE with increasing recirculation rate resulting from more oxygen transfer into the anode. However, increasing the recirculation rate within a low range significantly enhanced proton transfer in MFC-BL, resulting in a higher voltage output, a longer batch time, and a higher CE. A further increase in recirculation rate decreased the batch time and CE of MFC-BL due to excess oxygen transfer into anode outweighing the proton-transfer benefits. The unbuffered MFC had an optimal recirculation rate of 0.35 ml/min.