One-dimensional nickel(ii) coordination polymers of 9-anthracenyl-4′-benzoate and bispyridyl linkers as efficient electrocatalysts for hydrogen and oxygen evolution reactions

Abstract

Developing stable, efficient, and affordable Earth-abundant transition metal-based electrocatalysts for water splitting applications is key to producing green hydrogen. This study reports the development of new Ni(II)-based one-dimensional coordination polymers (CPs), namely, [Ni(9-AnBz)₂(4,4′-bpy)₂(MeOH)₂] (CP 1), [Ni(9-AnBz)₂(4,4′-bpe)₂(MeOH)₂] (CP 2), and [Ni(9-AnBz)₂(3,3′-bpdb)₂(H₂O)₂]·H₂O (CP 3) (where 9-AnBz = 9-anthracenyl-4′-benzoate, 4,4′-bpy = 4,4′-bipyridine, 4,4′-bpe = trans-1,2-bis(4′-pyridyl)ethene, and 3,3′-bpdb = 1,4-bis(3′-pyridyl)-2,3-diaza-1,3-butadiene), as novel electrocatalysts. Their structures have been confirmed by single crystal X-ray diffraction. These Ni(II)-based CPs exhibited improved electrocatalytic activity towards both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in 1.0 M KOH. The CP 1 catalyst was found to deliver a low HER onset potential (∼−0.04 V vs. RHE), a small HER overpotential (∼87 mV at −10 mA cm⁻²), a Tafel slope of ∼107.0 mV dec⁻¹, high current density (−496 mA cm⁻² at ∼1.83 V vs. RHE), and high mass activity (∼50.0 A g⁻¹), comparable to those of commercial Pt/C. Moreover, the CP 1 catalyst also exhibited the best OER activity, with a small overpotential (∼370 mV at 10 mA cm⁻²) and a low Tafel slope (∼82 mV dec⁻¹), showing efficient performance and great promise in hydrogen production systems.