帮我润色一下这段话：Developing efficient and earth-abundant bifunctional catalysts for both oxygen evolution reaction OER and hydrogen evolution reaction HER in basic media is critical to renewable energy conve

Developing efficient and sustainable bifunctional catalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in basic media is crucial for renewable energy conversion technologies. In this study, a 3D hierarchical heterostructure NiCoLDH@NiCoS@NiFeLDH electrode was successfully synthesized on a nickel foam substrate by coupling NiFeLDH nanosheets with NiCoS particles that were non-clumpingly anchored on the NiCoLDH nanosheets. The resulting 3D hierarchical heterostructure, with its typical three-dimensional structure and abundant heterogeneous interfaces, not only exhibited excellent catalytic activity for OER, with low overpotentials of 219 and 247 mV required to achieve current densities of 50 and 100 mA cm-2, respectively, which is lower than most recently reported earth-abundant electrocatalysts, but also efficiently catalyzed HER with a low overpotential of 93 mV at a current density of 10 mA cm-2 in alkaline electrolyte. Moreover, Tafel analysis and electrochemical impedance spectroscopy showed favorable kinetics during electrolysis. Importantly, the NiCoLDH@NiCoS@NiFeLDH electrode was used as both the cathode and anode in 1 M KOH for overall water splitting, which required a cell voltage of 1.61 V to achieve a current density of 10 mA cm-2 with excellent stability