Conjugated polycarboxylate ligand-coordinated NiFe LDH for enhanced oxygen evolution

Abstract

Nickel–iron layered double hydroxide (NiFe LDH) shows great performance in the oxygen evolution reaction (OER) due to the interaction between Ni and Fe. However, such an interaction still remains insufficient to achieve lower overpotential. To address this, we employ conjugated polycarboxylate ligands to promote electron transfer between Ni and Fe in NiFe LDH. This results in the formation of high-valence Ni in NiFe LDH, and also strengthens the adsorption of O intermediates at Ni sites. In this study, oxalate and 1,3,5-benzenetricarboxylate (BTC) are used to modify NiFe LDH, synthesized via the gas–solid reaction method and the decomposition of MIL-100(Fe) method, respectively. Oxalate-modified NiFe LDH has a low overpotential of 238 mV and Tafel slope of 38.1 mV dec⁻¹, while BTC-modified NiFe LDH is 230 mV and 36.1 mV dec⁻¹. In addition, both of them can work stably for over 24 h at a current density of 100 mA cm⁻². The conjugated polycarboxylate ligand modification method is a new strategy to promote the OER performance and extend long-term stability of NiFe LDH.