Multi‐layer Architecture of Novel Sea Urchin‐like Co‐Hopeite to Boosting Overall Alkaline Water Splitting

Abstract Electrochemical water splitting coupled with renewable energy offers a promising avenue for energy conversion and storage, but it is also extremely suppressed by the sluggish kinetics of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, a multi‐layer architecture strategy was utilized by the in situ growth for cobalt phosphate of Hopeite‐like phase (Co‐H) on NiCo‐layered double hydroxide (NiCo‐LDH) to prepare a self‐supported electrode (Co‐H/NiCo@NF). The Co‐H formed over the NiCo‐LDH shows a unique sea urchin‐like morphology. The Co‐H/NiCo@NF displays excellent HER and OER activity, requiring only overpotentials of 180 mV and 350 mV to deliver 100 mA cm⁻², consequently, be capable to generate an appealing cell potential of 1.76 V for overall water splitting at the corresponding current density. In addition, the prepared Co‐H/NiCo@NF has long‐term stability against 500 mA cm⁻² and exhibits a trend of increased activity, which may associate with the structural reconstructions to form new phases and the strong bonding between layers. These findings demonstrate that the multi‐layer architecture with fine‐component modulation is a promising strategy for the development of robust and efficient cobalt phosphate electrocatalysts, and the role of multi‐layer in the evolution of structural reconstructions deserves further investigation.