Using nanocrystals with specific crystal facets is an effective way to enhance activity and selectivity for numerous catalytic reactions . However, the intrinsic facet effect is not fully understood. Herein, using Pt catalyzed glycerol oxidation reaction as the model system, the intrinsic facet effect on catalytic property is evaluated by three kinds of Pt nanocrystal catalysts with cubic, spherical and tetrahedral shapes. Size effect, support effect, surfactant effect as well as the metal-support interaction of the catalysts are avoided to the maximum extent. The supported Pt nanocubes enclosed by Pt(1 0 0) facets are found to exhibit much higher catalytic activity and stability for the aerobic oxidation of glycerol than catalysts with Pt nanotetrahedrons enclosed by Pt(1 1 1) facets. DFT calculations indicate that the adsorption of oxygen and glycerol would materialize easier on Pt(1 0 0) than on Pt(1 1 1). Furthermore, Pt(1 0 0) may prevent deactivation caused by product adsorption as well.
One important approach to address the cost issue of fuel cells is to maximize the utilization of Pt by reducing its loading and enhancing the performance for the oxygen reduction reaction (ORR) as well as durability of catalysts. In this work, a one-step synthesis of highly dispersed low-Pt (1 1 1) electrocatalysts (p-Pt/KBs) supported by Ketjenblack is conducted using interaction between solution and nonthermal plasma (SNP). The results show that the plasma-treated platinum precursor dispersion efficiently avoids particle agglomeration and increases more defects of the support surface, which are conducive to the trapping and anchoring of platinum nanoparticles (Pt NPs). The catalyst (p-Pt/KB-NaOH) with a platinum load of 10.8 wt% is obtained by adding sodium hydroxide to the platinum precursor dispersion solution, showing better ORR performance (E 1/2 = 0.88 V) and stability compared to the commercial platinum on carbon (Pt/C) catalyst (20 wt%, E 1/2 = 0.86 V). This improvement is attributed to the fact that neutralizing chloroplatinic acid slows down the reduction rate of the platinum precursor, effectively controlling the rapid nucleation and slow crystal growth of platinum. As the cathode catalyst for PEMFCs, p-Pt/KB-NaOH exhibits remarkable mass-transfer performance in the high-current density domain (HCD), with maximum power density (P max ) of 1131 mW cm −2 at 2500 mA cm −2 , which is 9.1 % higher than commercial Pt/C. Moreover, the single-cell operates stably for at least 100 h at 1000 mA cm −2 with a negligible decay (1.9 %) of the working voltage, ensuring long-term durability.
Shizhu Song,Qi Li,Lifang Zhang,Yanqing Wang,Xiaojuan Liu
Here, N -doped hollow carbon sphere (NHCS)-supported (1 1 1)-plane-engineered sub-5-nm Pt (Pt-NHCS) catalysts regulated precisely by imidazolium ionic liquids were synthesized successfully and used to catalyze oxygen reduction. The (1 1 1)-plane engineered Pt nanocrystals with a diameter of 4.5 ± 0.5 nm were homogeneously deposited on the 3-dimensional spherical nanoshells. The resulting Pt nanocrystals anchored on the carbon skeleton exhibit a stable configuration in both alkaline and acid electrolytes with the help of imidazolium cations and pyrolysis. Among all as-prepared catalysts, the optimized Pt-NHCS shows remarkable long-term durability. Specifically, Pt-NHCS maintains 95.3% of the original current density after 10,000 potential cycles, while Pt/C benchmarks exhibit a retention of 78.5%. Accelerated durability test results indicate that Pt-NHCS exhibits a high efficiency of 96 % in comparison with initial current density, while a value of 86% for Pt/C. Density functional theory calculations demonstrate that reactive Pt(1 1 1) planes with well-defined Schottky defects and vacancies adsorb and activate oxygen molecule rapidly while desorbing the reaction intermediates.
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