Carbon-Free CoO Mesoporous Nanowire Array Cathode for High-Performance Aprotic Li–O₂ Batteries

Although various kinds of catalysts have been developed for aprotic Li–O₂ battery application, the carbon-based cathodes are still vulnerable to attacks from the discharge intermediates or products, as well as the accompanying electrolyte decomposition. To ameliorate this problem, the free-standing and carbon-free CoO nanowire array cathode was purposely designed for Li–O₂ batteries. The single CoO nanowire formed as a special mesoporous structure, owing even comparable specific surface area and pore volume to the typical Super-P carbon particles. In addition to the highly selective oxygen reduction/evolution reactions catalytic activity of CoO cathodes, both excellent discharge specific capacity and cycling efficiency of Li–O₂ batteries were obtained, with 4888 mAh g_CoO^–1 and 50 cycles during 500 h period. Owing to the synergistic effect between elaborate porous structure and selective intermediate absorption on CoO crystal, a unique bimodal growth phenomenon of discharge products was occasionally observed, which further offers a novel mechanism to control the formation/decomposition morphology of discharge products in nanoscale. This research work is believed to shed light on the future development of high-performance aprotic Li–O₂ batteries

Irregularities in Product Distribution of Fischer–Tropsch Synthesis Due to Experimental Artifact

Experimental product distribution of Fischer–Tropsch synthesis frequently presents notable deviations from the typical double-α Anderson–Schulz–Flory pattern: bump or dip around the breaking carbon number, positive or negative deviation for heavy hydrocarbons. These irregularities were studied experimentally in a fixed-bed reactor over an industrial Fe/Mn catalyst, and theoretically by a product separation model based on Aspen Plus software. First, it was found that the unsteady state of reaction condition or improper gas chromatograph procedure could lead to deviation for heavy hydrocarbon distribution. Second, the bump near the breaking carbon number could be attributed to the accumulation of water in hot trap, which leads to an inaccurate measurement of the wax amount. This irregularity can be eliminated by selecting either a higher temperature or a lower pressure of the hot trap. Third, vaporization or flash loss of the oil sample during product collection could result in dip in light hydrocarbon distribution. High syngas conversion levels should be avoided for accurate data acquirement