Trisodium Citrate-Assisted Synthesis of Edge-Abundant Nickel-Iron Layered Double Hydroxides for Efficient Oxygen Evolution Reaction

Abstract

The edges of layered double hydroxides (LDHs) display an exceptionally more efficient oxygen evolution reaction (OER) activity than the (001) basal plane as demonstrated by both theoretical calculations and experimental studies. However, a controllable synthesis method of LDHs with abundant edges has yet to be described. Herein, we report a strategy enabling the synthesis of nickel-iron LDHs with abundant edges (NiFe LDHs-E) based on the use of citrate anions as the structure-directing agent. The edge density is characterized using spectroscopy techniques and its OER performance is compared with that of nickel-iron LDHs with abundant basal planes (NiFe LDHs-B). In alkaline electrolyte (1 M KOH), NiFe LDHs-E exhibits excellent OER activity with very low overpotential (235 mV at 10 mA cm−2) and current densities (at η = 320 mV) up to sixfold higher than those of NiFe LDHs-B. Density functional theory (DFT) calculations confirm the high OER activities ascribed to the abundant side-plane edges with optimal strength of binding of OER intermediates. Overall, a comprehensive investigation, employing both experimental and computational methodologies, yields new insights to fabricate superior catalysts meticulously designed with specific crystal planes and unveils the crucial structural attributes, thus unleashing the limitless potential of the catalytic domain.