Curtailing the Excess eg-Orbital Filling of a Ni Atom by Enhanced Interatomic Charge Transfer within a Bimetallic 2D Metal–Organic Framework for the Oxygen Evolution Reaction

Abstract

Electrochemical conversion technologies rely on the design and creation of highly efficient electrocatalysts. The oxygen evolution reaction (OER), which has applications in water splitting and metal–air batteries, is a crucial process in such conversions. Herein, a bimetallic Co, Ni-based ultrathin metal–organic framework nanoribbon (NiCo-NR) is reported for an efficient OER. It is proposed that in ultrathin MOF nanoribbons, the surface atoms (Co, Ni) are coordinatively unsaturated, due to which the interatomic electron transfer within the MOF makes more active adsorption sites on the surface. The catalyst exhibits an overpotential of 244 mV at a current density of 10 mA cm–2 with a Tafel slope value of 85 mV dec–1. For the stability experiment, the catalyst was exposed for 35 h of uninterrupted operation at a current density of 100 mA cm–2. Our findings showed that coordinatively unsaturated transition metal atoms were dominant active sites and the electrocatalytic activity can be tuned by the coupling interactions of Ni and Co metals. The excess eg-orbital filling of the Ni atom, which limits the electrocatalytic performance, can be reduced by π-donation from Ni to Co through the oxygen atom.