Technical Report 193, c4e-Preprint Series, Cambridge

Authors: Yuan Sheng, Maria Botero, Manoel Y. Manuputty, Markus Kraft, and Rong Xu

Reference: Technical Report 193, c4e-Preprint Series, Cambridge, 2017

Associated Themes:
 

• Co₃O₄ and Fe_xCo_3-xO₄ nanoparticles/nanostructured films were prepared by vapor-fed flame aerosol synthesis for the first time.
• The morphology of the films was tunable from columnar to granular by changing precursor concentration in the flame mixture.
• The nanoparticles exhibited a comparable electrocatalytic oxygen evolution activity with that of wet-chemically synthesized benchmarks.
• The as-prepared catalyst films can serve as water splitting electrodes directly without further treatment.

Synthesis of earth-abundant nanocatalysts for the oxygen evolution reaction (OER) has depended largely on highly diluted, batchwise wet chemical methods, leaving it a challenge to improve throughput and sustainability of the process. Herein, we demonstrate for the first time the production of Co₃O₄ and Fe_xCo_3-xO₄ nanoparticles using vapor-fed flame aerosol synthesis (VFAS), a continuous and scalable process requiring minimal waste treatment. In 1M KOH, the catalysts exhibit stable OER overpotentials of 295 mV @ 10 mA/cm² and Tafel slopes down to 38 mV/dec, which are comparable to the performances of wet-chemically derived benchmark (Fe-doped) Co₃O₄ catalysts. The high activity is attributed to ultrafine particle size of <D_p> = 3.1-4.4 nm and rich surface defects. Furthermore, nanostructured Co₃O₄ and Fe_xCo_3-xO₄ films can be conveniently grown on graphite substrates by VFAS and serve as OER electrodes without further treatment. Remarkably, the morphology of the films can be easily tuned from columnar to granular by varying precursor concentration in feed gas, achieving optimal utilization of catalytic materials with a hierarchical structure consisting of elongated nanoparticulate building blocks.

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