Synergistic design of multiphase Fe–Ni–Co coatings and gravity-aligned pore architecture for high-performance water splitting on Ti–6Al–4V

The development of noble-metal-free electrodes for water splitting is essential for advancing industrial hydrogen production. Transition metal oxides, hydroxides, and oxyhydroxides based on Fe, Co, and Ni have been widely studied as catalysts for water electrolysis. However, research on growing catalysts on bubble-managing substrates remains limited. In this work, Fe 0.6 Ni 0.2 Co 0.2 was optimized for coating on a porous Ti-6Al-4V substrate, followed by electrochemical oxidation, yielding a bifunctional catalyst layer composed of Fe 2 O 3 , NiO, CoO, Fe 0.3 Co 0.7 O x , Fe 0.25 Ni 0.75 O x , along with their hydroxides and oxyhydroxides. Moreover, aligning the pore axis with gravity promotes buoyancy-driven bubble release, thus reducing electrode polarization. When employed for overall water splitting in this optimized orientation, the electrode with a pore cross-section of 1040 μm achieved a current density of 100 mA/cm 2 at a voltage of only 1.634 V. This study provides valuable insights and a reference framework for the design and development of efficient, low-cost electrodes for water electrolysis.