Enhanced bifunctional electrocatalytic performance of NiFe-layered double hydroxide activated by ultrasonic-assisted loading of Pd nanoclusters

Abstract

In this study, metallic Pd nanocrystals loaded on NiFe-layered double hydroxide (Pd/NiFe-LDH-u) electrocatalyst for water splitting is synthesized via a novel ultrasonic-assisted ion exchange and in situ reduction method. The ultrasonic-assisted loaded Pd clusters (with an average size 2.84 nm) are in high crystallinity. The optimized Pd/NiFe-LDH-u displays remarkable oxygen evolution reaction (OER) catalytic activity with a low overpotential of 267 mV at 20 mA cm−2. The hydrogen evolution reaction (HER) mass activity of Pd/NiFe-LDH-u is up to 6.37 A mg−1 at an overpotential of 300 mV, which is nearly 10 times higher than that of bare Pd and outperforming most reported Pd-based catalysts. Both the experimental results and density functional theory (DFT) calculations prove that the ultrasonic-assisted loading effectively strengthens the interaction between Pd and NiFe-layered double hydroxide (NiFe-LDH), resulting in improved dispersion uniformity, catalytic stability, electrical conductivity and bifunctional catalytic activities.