• Alothman, Zeid A.
• Jiang, Xuchuan
• Septiani, Ni Luh Wulan
• Guo, Yanna
• Kaneti, Yusuf Valentino
• Yamauchi, Yusuke
• Iqbal, Muhammad
• Yuliarto, Brian
• Takei, Toshiaki

Abstract

<p>Hierarchical nanostructures with hollow architectures can provide rich active sites, improved transport of ions, and highly robust structure for electrochemical applications. In this work, we report the self-templated fabrication of hierarchical manganese-cobalt phosphide (Mn-Co phosphide) yolk-shell spheres using highly uniform cobalt glycerate spheres as sacrificial templates. Through a simple exchange reaction with the manganese precursor solution at room temperature, these cobalt glycerate spheres are readily converted to hierarchical Mn-Co LDH yolk-shell spheres, which can be further phosphidized at 350 °C under inert atmosphere to generate hierarchical Mn-Co phosphide with distinct yolk-shell morphology. When tested as an electrocatalyst for oxygen evolution reaction (OER), the hierarchical Mn-Co phosphide yolk-shell spheres exhibit an overpotential of 330 mV at a current density of 10 mA cm⁻² and a Tafel slope of 59.0 mV dec^-1, which are higher than those of Mn-Co oxide yolk-shell spheres (480 mV and 113 mV dec^-1) and hierarchical cobalt phosphide spheres (410 mV and 61.3 mV dec^-1). Post-OER analysis by XPS reveals that the high activity of the hierarchical Mn-Co phosphide yolk-shell catalyst originates from the existence of Mn⁴⁺/Mn³⁺ and Co²⁺/Co³⁺ redox couples and the formation of active metal oxyhydroxide species on its surface. The proposed self-sacrificial templating strategy will provide useful guidance for future construction of hollow inorganic metal nanostructures with yolk-shell morphology for energy storage and conversion applications.</p>

Topics

• density
• morphology
• surface
• x-ray photoelectron spectroscopy
• Oxygen
• cobalt
• current density
• Manganese