A highly efficient and robust hybrid structure of CoNiN@NiFe LDH for overall water splitting by accelerating hydrogen evolution kinetics on NiFe LDH

Abstract Hydrogen production by electrochemical overall water splitting is considered as a clean and renewable approach for greener energy. However, the efficiency of water electrolysis suffers from the sluggish kinetics and high overpotential of OER. Although NiFe LDH is regarded as a promising OER catalyst, it faces the problem of poor conductivity, resulting in the limitations of HER performance. Herein, a hybrid nano-architecture of CoNiN@NiFe LDH as a bifunctional electrocatalyst for overall water splitting is fabricated via in-situ electrochemically assembling hierarchical NiFe LDH nanosheets on the surface of CoNiN. CoNiN@NiFe LDH shows excellent activities for OER with the overpotentials of 227 and 291 mV to deliver the current densities of 10 and 100 mA cm−2, respectively. Moreover, an alkaline electrolyzer with CoNiN@NiFe LDH as anode and cathode requires a cell voltage of 1.63 V to achieve 10 mA cm−2. In addition, the excellent stability with 100 h towards overall water splitting outperforms most transition metal-based bifunctional electrocatalysts. The superior performance is attributed to the abundant active sites, the strong electronic interaction, and the corresponding metal (oxy)hydroxides species generated by in situ surface reconstruction and phase transformation.