Fe₃O₄-CoP_x Nanoflowers Vertically Grown on TiN Nanoarrays as Efficient and Stable Electrocatalysts for Overall Water Splitting

Development of efficient electrocatalysts for overall water splitting is an attractive and challenging task. Here, we present a simple one-step electrodeposition for the synthesis of ferroferric oxide (Fe3O4) decorated cobalt monophosphide (CoPx) nanoflowers formed on titanium nitride (TiN) nanoarrays. Accompanied with the TiN nanoarrays as a support, the synthesized Fe3O4–CoPx/TiN exhibits an excellent activity with an onset potential of 50 mV as well as superior stability even after 100 h for hydrogen evolution reaction (HER). Besides, the Fe3O4–CoPx/TiN composite delivers a current density of 10 mA cm–2 at a low overpotential of 331 mV for oxygen evolution reaction (OER), which outperforms the Ir-based noble-metal catalysts. Remarkable activities for HER and OER are ascribed to the synergetic effects among each component and the reinforced structural stability. Specifically, the incorporation of Fe3O4 into phosphide promotes the electron donor–acceptor properties during the catalytic progress that leads to a significant activity enhancement. Simultaneously, the TiN nanoarrays not only offer multi-charge-transfer channels to facilitate the electronic procedure, but also help to anchor and uniform the Fe3O4–CoPx nanoflowers without aggregation, further enabling a dynamic stability of the composite. Therefore, this work highlights the favorable integration of Fe3O4, CoPx, and TiN, which provides a way for constructing the hybrid structure for high-performance water splitting.