Highly efficient Ni nanotube arrays and Ni nanotube arrays coupled with NiFe layered-double-hydroxide electrocatalysts for overall water splitting

Novel nickel nanotube arrays (NTAs) on foamed nickel (NF) are developed by a facile electrochemical dealloying method to achieve a high hydrogen evolution reaction. Meanwhile, three dimensional heterostructure NiFe layered-double-hydroxide (LDH)@Ni NTAs electrode materials with strong interfacial interaction are prepared on NF by coupling ultrathin NiFe LDHs with Ni NTAs by electrochemical deposition, which demonstrate an excellent catalytic performance for oxygen evolution compared with NiFe LDH. Ni NTAs/NF require an overpotential of 101 mV to force the current density of 10 mA cm(-2) for hydrogen evolution reaction because of the unique NTAs structure and the active sites for water dissociation provided by Ni2+ on the Ni NTAs surface. NiFe LDH@Ni NTAs/NF exhibit a low overpotential of 191 mV at a current density of 10 mA cm(-2) for oxygen evolution reaction due to the reliable electron transfer from the intermediate metallic Ni NTAs to the external the NiFe LDH layer and more active sites that are exposed by highly dispersed ultrathin NiFe LDH nanosheets. The development of self-supporting NiFe LDH@Ni NTAs and Ni NTAs electrodes for efficient overall water splitting in an integrated alkaline electrolyzer is achieved a current density of 10 mA cm(-2) at 1.51 V, accompanying excellent long-term durability.