Out-of-Plane Ligands on Quaternary-Metal Layered Double Hydroxides Modulate Interfacial Water Hydrogen-Bond Network for Efficient Oxygen Evolution.

Abstract

The oxygen evolution reaction (OER), involving a sluggish four-electron transfer process, is the main bottleneck limiting the efficiency of water electrolysis. Although layered double hydroxides (LDHs) are recognized as promising alkaline OER catalysts, further reducing the reaction energy barrier and gaining mechanistic insight into the role of interfacial water remain critical challenges. Herein, we construct a quaternary-metal LDH with out-of-plane organic ligands and investigate how the strongly electron-withdrawing BDC(F)4 ligand regulates interfacial water. The resulting RuNiMnFe LDH-BDC(F)4 catalyst exhibits excellent OER performance, achieving a low overpotential of 204 mV at 10 mA cm-2, lower than that of the counterpart without the out-of-plane ligand. In situ Raman spectroscopy reveals the optimization of the hydrogen-bond network of interfacial water in the presence of BDC(F)4. The results indicate that the proportion of weakly coordinated double-hydrogen-bond water, a favorable interfacial water configuration for OER, increases to over 60%, while inactive free water molecules are substantially reduced. This work not only provides an effective strategy for designing high-performance OER electrocatalysts but also highlights the key role of the interfacial water hydrogen-bond network in electrocatalysis.

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