We report CoFe<sub>2</sub>O<sub>4</sub> nanoparticles (NPs) synthesized using a facile hydrothermal growth
and their attachment on 3D carbon fiber papers (CFPs) for efficient
and durable oxygen evolution reaction (OER). The CFPs covered with
CoFe<sub>2</sub>O<sub>4</sub> NPs show orders of magnitude higher
OER performance than bare CFP due to high activity of CoFe<sub>2</sub>O<sub>4</sub> NPs, leading to a small overpotential of 378 mV to
get a current density of 10 mA/cm<sup>2</sup>. Significantly, the
CoFe<sub>2</sub>O<sub>4</sub> NPs-on-CFP electrodes exhibit remarkably
long stability evaluated by continuous cycling (over 15 h) and operation
with a high current density at a fixed potential (over 40 h) without
any morphological change and with preservation of all materials within
the electrode. Furthermore, the CoFe<sub>2</sub>O<sub>4</sub> NPs-on-CFP
electrodes also exhibit hydrogen evolution reaction (HER) performance,
which is considerably higher than that of bare CFP, acting as a bifunctional
electrocatalyst. The achieved results show promising potential for
efficient, cost-effective, and durable hydrogen generation at large
scales using earth-abundant materials and cheap fabrication processes