Tuning the d-band states of NiFe-MOFs by combining early and late transition metals for enhanced electrocatalytic oxygen evolution

Abstract

Electronic modulation is of great importance in an attempt to enhance the catalytic activity of electrocatalysts towards the oxygen evolution reaction (OER), which dominates the energy efficiency of water splitting. Here, a facile and reliable strategy is reported based on the specific synergistic effects of the combination of early and late transition metals. The OER activity of a prototypical bimetallic NiFe-MOF was greatly promoted by introduction of a Cr ion dopant, and the as-prepared Cr-NiFe-MOF needed a low overpotential of only 242 mV to deliver a current density of 100 mA cm⁻² with excellent stability. Detailed analyses revealed that Cr replaced the position of Ni in the NiFe-MOF and adjusted the electronic structure of nearby Fe sites, allowing the d-band center to shift down to efficiently regulate the adsorption behavior of key intermediates, which endowed the Cr-neighboring Fe sites with a lowered energy barrier for the OER. This work presents a strategy of early-and-late transition metal combination to provide new pathways for efficient water splitting catalyst development.