Activating nickel iron layer double hydroxide for alkaline hydrogen evolution reaction and overall water splitting by electrodepositing nickel hydroxide

NiFe-layer double hydroxide (NiFe-LDH) has been widely explored for oxygen evolution reaction (OER), but only a few works have been done for hydrogen evolution reaction (HER). Herein, NiFe-LDH is activated for HER and overall water splitting by depositing Ni(OH)2 nanoparticle to form NiFe-LDH/Ni(OH)2 composite electrocatalyst using two-step electrodeposition method. The electrocatalytic performance of NiFe-LDH/Ni(OH)2 in alkaline condition greatly improves as compared to that with single-phase NiFe-LDH or Ni(OH)2. At a higher overpotential of − 0.3 V, NiFe-LDH/Ni(OH)2 composite could reach a current density of 180 mA/cm2 which increases 3-fold as compared to a single-phase NiFe-LDH (60 mA/ cm2). More importantly, NiFe-LDH/Ni(OH)2 composite can act as a bifunctional electrocatalyst for overall water splitting. The cell voltages at current densities of 10 and 100 mA/cm2 are 1.6 and 1.8 VRHE, respectively during the water splitting process. The great improvement of electrocatalytic activities after the formation of composite catalysts is due to the synergetic effect between NiFe-LDH and Ni(OH)2 to efficiently accelerate the water dissociation step and electron transfer through Ni(OH)2 layer. This work provides simple and robust electrodeposition technique to prepare NiFe-LDH/Ni(OH)2 composite for activating HER and overall water splitting.