Alkali treatment of layered double hydroxide nanosheets as highly efficient bifunctional electrocatalysts for overall water splitting

Efficient and economic bifunctional electrocatalyst for water splitting to produce hydrogen is urgently required. The layered double hydroxides (LDHs) have shown superior activity for oxygen evolution reaction (OER) for water electrolysis, while their hydrogen evolution reaction (HER) activity remains challenging. Herein, we report an alkali hydrothermal-treatment strategy to enhance the HER as well as OER performance of NiCo-LDH. This method can create metal vacancies and newly formed Ni/Co(OH)2 phase over NiCo-LDH, tune the electronic structure, and improve the electrical conductivity, thereby improving the electrochemical activity. The NiCo-LDH-OH catalyst delivers a current density of 10 mA cm−2 at an overpotential of 180 mV for HER and an overpotential of 317 mV for OER, which is greatly reduced compared to the pristine NiCo-LDH (295 mV for HER and 336 mV for OER). When assembled into an electrolyzer both as a cathode and anode, it demonstrates superior activity for overall water splitting with no obvious decay after 20 h. This work paves a new path for fabricating efficient LDHs-based HER/OER bifunctional catalysts.