Spindle-shape ferric oxyhydroxides with nano-sized grains for efficient oxygen evolution reaction and supercapacitors

The rational design and development of novel electrode materials with a unique hierarchical nanostructure is crucial for improving their electrochemical activities, charge transfer kinetics, energy efficiency, and energy-storing ability in energy conversion and storage devices. In this study, we synthesized spindle-shaped ferric oxyhydroxide nanoparticles directly grown on carbon cloth (spindle-FON/CC) by a facile and straightforward hydrolysis method. This material is a promising candidate for the fabrication of efficient electrodes used in supercapacitors (SCs) and electrocatalytic cells for the oxygen evolution reaction (OER). The as-prepared spindle-FON/CC exhibits unique structural features with nano-sized grains and pores that provide large electrolyte contact areas (electrochemically active sites) and favorable ion diffusion pathways. These structural properties lead to efficient capacitive behavior and electrochemical catalytic activity. The as-prepared spindle-FON/CC electrode showed a high specific capacitance of 612.5 mF cm⁻² and outstanding cycling stability (95.7 % capacitance retention after 4,000 cycles). When used as an OER electrocatalyst, the spindle-FON/CC exhibited improved electrocatalytic activity with a low overpotential of 216 mV at a current density of 10 mA cm⁻² and a small Tafel slope of 73.4 mV dec⁻¹.