Controllable design of 3D hierarchical Co/Ni-POM nanoflower compounds supported on Ni foam for the hydrogen evolution reaction

Abstract

Polyoxometalates (POMs) as precursors to form non-noble metal containing composites for the hydrogen evolution reaction (HER) have attracted an increasing amount of research attention, as they can be structurally modified at the molecular level without undergoing any structural changes upon multi-electron transfer. Herein, a novel mixed metal 3D nanoflower POM-based composite (Co/Ni-POM) on Ni foam (denoted as Co/Ni-POM/NFs) was prepared as an electrocatalyst for the HER, with tunable synthesis parameters. The optimized Co/Ni-POM/NF sample exhibits excellent catalytic activity and high stability, manifesting in an overpotential of only 68 mV for the HER (10 mA cm⁻²) and a Tafel slope of 60.8 mV dec⁻¹ in 1 M KOH. The outstanding catalytic activity of Co/Ni-POM/NF stems from the synergistic effect between the metallic elements of the Co/Ni-POM and its large specific surface area. The Co/Ni-POM tightly riveted on nickel foam during the catalytic process also shows that the as-prepared catalyst is an excellent material for use in the HER.