Sequential construction of Ru/B-regulated crystalline-amorphous interfaces in MOF-derived NiCo-LDH enables highly efficient bifunctional electrocatalysis.

Although Metal-Organic Framework (MOF)-derived NiCo layered double hydroxides (LDHs) provide ideal hierarchical architectures for multifunctional interface engineering, rationally integrating such interfaces to cooperatively regulate the electronic structure and kinetics of both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) remains a significant challenge in high current alkaline water electrolysis. Herein, B-Ru-NiCo-LDH nanosheet arrays featuring crystalline-amorphous heterophases were constructed on nickel foam (NF) through sequential Ru3+ incorporation and alkaline NaBH4 treatment, which simultaneously generated crystalline Ru nanoparticles and introduced B into the amorphous NiCo-LDH matrix. High-resolution transmission electron microscopy (HR-TEM) analyses reveal distinct lattice fringes of Ru in intimate contact with the amorphous NiCo-LDH framework, confirming the formation of crystalline-amorphous interfaces. Moreover, the systematic binding-energy shifts observed in the high-resolution Ni 2p and Co 2p spectra obtained by X-ray photoelectron spectroscopy (XPS) provide strong evidence for pronounced electronic modulation and interfacial charge redistribution within the NiCo-LDH scaffold. Consequently, the B-Ru-NiCo-LDH electrocatalyts demonstrate excellent activity in 1.0 M KOH, requiring overpotentials of only 68 and 229 mV to achieve HER current densities of 10 and 300 mA cm-2, respectively, while delivering OER overpotentials of 201 and 322 mV at the corresponding current densities. When being used as bifunctional catalyst, the resulting B-Ru-NiCo-LDH (+) ‖ B-Ru-NiCo-LDH (-) electrolyzer requires only 1.48 V and 1.92 V to deliver 10 mA cm-2 and 500 mA cm-2, respectively, and maintained stable operation for 160 h at 100 mA cm-2, retaining ca. 95% of its initial performance. The superior performance can be attributed to the synergistic effects of NaBH4-induced electronic modulation and strong coupling between crystalline Ru and amorphous NiCo-LDH, which may facilitate interfacial charge transfer and optimize the adsorption of key reaction intermediates. This work provides a versatile strategy for engineering crystalline-amorphous interfaces toward durable, high-current-density alkaline water electrolysis.