Fabrication of FeNi hydroxides double-shell nanotube arrays with enhanced performance for oxygen evolution reaction

FeNi Hydroxides (FeNi-HD) have been considered as promising substitutes to noble metal electrocatalysts for oxygen evolution reaction (OER). In this work, we design and realize FeNi-HD nanotube arrays (FeNi-HDNAs) on Ni foam via an in-situ reaction and Kirkendall effect. The obtained catalysts possess higher specific surface area, more catalytic active sites and better chemical stability for OER. Electron migrations from the Fe 3d orbitals to Ni sites in the FeNi-HDNAs lead to more unoccupied Fe 3d states and a higher oxidation state. As expected, FeNi-HDNAs exhibit lower overpotential as well as lower Tafel slope and better durability than the Fe- or Ni-HD peers. DFT calculations elucidate that FeNi hydroxides lower the energy barrier of rate-determining step in OER. Moreover, a high current density of 10 mA cm(-2) is obtained at a low potential of 1.49 V using FeNi-HDNAs as the bifunctional electrocatalyst for overall water splitting in basic solution.