dc.description.abstract | Direct methanol fuel cells (DMFCs) have attracted considerable interest because of a variety of merits such as low operating temperatures, easy fuel-feeding, and the high energy density of methanol (6.09 kWh kg-1). However, it also has some disadvantages, for example, low power density, Pt poison by CO, methanol crossover, and high cost for catalysts. In this study, we focuse on the improvement in electrochemical performance, CO tolerance, and life time of catalysts.
Due to the research by the literature, the traditional carbon support is susceptible to corrosion under the harsh conditions, and has weakly interaction with catalytic metal, which will result in the degradation of catalyst performance and life time. So we try to use metal ceramic materials like titanium dioxide (TiO2), titanium carbide (TiC), and titanium nitride (TiN), which are plausible support materials due to their electrochemical and thermal oxidation stability and corrosion resistive nature under electrochemical oxidation condition. In this study, we present the studies using titania and carbon hybrids as supports to prepare PtRu/TiO2-C(1:1), PtRu/TiC-C(1:1), and PtRu/TiN-C(1:1) catalysts system.
PtRu catalysts prepared using PtRu/TiO2-C(1:1), PtRu/TiC-C(1:1), and PtRu/TiN-C(1:1) supports shows the nanoparticles are highly dispersive and exhibit smaller particle sizes (3.4 to 4.0 nm) on the TiO2, TiC, and TiN supports compared to that on Vulcan XC-72 carbon support (>4.0 nm). The Methanol oxidation reaction shows increasing activity from PtRu/E-TEK (667.3 A/g Pt), PtRu/CB (1128.1 A/g Pt), PtRu/TiO2-C(1:1) (1278.0 A/g Pt), PtRu/TiC-C(1:1) (1598.5 A/g Pt), and PtRu/TiN-C(1:1) (1709.2 A/g Pt). The maximum MOR activity in PtRu/TiN-C(1:1) is found to be nearly twice that of conventional PtRu/E-TEK catalysts.
Strong metal interaction with Titanium is identified by XPS studies which yielding higher binding energy shift of the three Titania supports, explains the production of smaller particle size and the stability of the nano-participles after I-T curve these systems. This electronic effect also partly accounts for the improved MOR activity. On the effects of CO tolerance, the OH groups on TiO2 surface combines with Ru to remove the CO intermediate, and shows improved CO tolerance over that of TiC and TiN supports where the surface is free of any functional groups. This study demonstrated TiO2, TiC, and TiN are outstanding supports which inhibits the aggregation of PtRu, results in significantly increases MOR catalytic activity and stability. The best MOR activity observed at the PtRu/TiN-C(1:1) catalyst.
The DMFC comprising the PtRu/TiO2-C(1:1), PtRu/TiC-C(1:1), and PtRu/TiN-C(1:1) anode shows an impressive power density of 98.1 mW/cm2, 73.5 mW/cm2, and 80.0 mW/cm2 compared to a peak power density of 58.9 mW/cm2 found in the MEA (Membrane electrode assembly) with a PtRu /E-TEK anode at 80°C. The better CO-tolerance in the anode catalyst of PtRu/TiO2-C(1:1) originated from its better methanol affinity, for example is likely to be responsible for the better fuel cell out-put compared to the anode made from PtRu/TiN-C(1:1). | en_US |