Synergistic Modulation of Electronic Interaction to Enhance Intrinsic Activity and Conductivity of Fe-Co-Ni Hydroxide Nanotube for Highly Efficient Oxygen Evolution Electrocatalyst.

The large-scale hydrogen production and application through electrocatalytic water splitting depends crucially on the development of highly efficient, cost-effective electrocatalysts for oxygen evolution reaction (OER), which, however, remains challenging. Here, a new electrocatalyst of trimetallic Fe-Co-Ni hydroxide (denoted as FeCoNiO x H y ) with a nanotubular structure is developed through an enhanced Kirkendall process under applied potential. The FeCoNiO x H y features synergistic electronic interaction between Fe, Co, and Ni, which not only notably increases the intrinsic OER activity of FeCoNiO x H y by facilitating the formation of *OOH intermediate, but also substantially improves the intrinsic conductivity of FeCoNiO x H y to facilitate charge transfer and activate catalytic sites through electrocatalyst by promoting the formation of abundant Co 3+ . Therefore, FeCoNiO x H y delivers remarkably accelerated OER kinetics and superior apparent activity, indicated by an ultra-low overpotential potential of 257 mV at a high current density of 200 mA cm -2 . This work is of fundamental and practical significance for synergistic catalysis related to advanced energy conversion materials and technologies.