Macroporous Ni-Fe hydroxide bifunctional catalyst for efficient alkaline water splitting

Three-dimensional macroporous heterostructural Ni-Fe hydroxides with different mole ratio (Ni x Fe (1−x) -PH) were prepared via a sol-gel process combined with phase separation, and the overall water splitting electrocatalytic activity of the resultant macroporous Ni-Fe hydroxides were investigated in detail. The as-prepared Ni-Fe hydroxide has cocontinuous skeletons and interconnected macropores with a narrow pore size distribution (~150 nm), and possesses outstanding electrocatalytic activity with an overpotential of 263 mV for oxygen evolution reaction (OER) and 175 mV for hydrogen evolution reaction (HER) at 10 mA·cm −2 in 1 M KOH, respectively. The Ni 0.6 Fe 0.4 -PH | | Ni 0.6 Fe 0.4 -PH has efficient overall water splitting performance with a cell voltage of 1.61 V at 10 mA·cm −2 and great stability. The fantastic macropore structure and strong synergistic effect between Ni-Fe hydroxides significantly reinforce the contact area between the electrocatalyst and electrolyte, and endow high electrocatalytic performance of bifunctional electrocatalysts. The epoxide-induced sol-gel process accompanied by phase separation allows the synthesis of macroporous heterostructural Ni-Fe hydroxide bifunctional catalyst with a mass of active sites, displaying excellent electrocatalytic activity and low overpotential at several current densities for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).