Three-Dimensional Sm-Doped NiCu-LDH on Ni Foam as a Highly Robust Bifunctional Electrocatalyst for Total Water Splitting

In order to fulfill the increasing energy demand of the world, water electrolysis comes out to be an effective method for producing clean H2 fuel. To catalyze both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in water splitting, an effective and inexpensive bifunctional catalyst is highly required. To serve this purpose, 3d transition metal-based layer double hydroxides (LDH) proved to be an effective catalyst. Here, in this work, we have synthesized Sm-doped NiCu-LDH via a single-step hydrothermal method. The doping of rare-earth Sm ions in NiCu-LDH effectively modifies the electronic structure of NiCu-LDH by enhancing the activity of active metal sites. To catalyze the OER and HER, 10% Sm@NiCu-LDH demands only 347 and 192 mV overpotential to reach 50 mA cm–2 current density along with the Tafel slope values of 70 and 109 mV dec–1, respectively. After 10% Sm doping, the turnover frequency (TOF) value has been raised more than twofold compared to the bare NiCu-LDH. For total water splitting (TWS), when Sm@NiCu-LDH was used as both the anode and cathode, it demands only 1.629 V cell voltage to reach 10 mA cm–2 current density. Also, 10% Sm@NiCu-LDH shows excellent long-term stability and robust nature for 48 h in alkaline conditions. Sm doping effectively modifies the electronic structure of NiCu-LDH and results in improved catalytic activity. Therefore, this work paves the road toward searching highly stable bifunctional electrocatalysts by means of providing good activity and stability for effective total water splitting application.