Electronic modulation of iridium single atomic sites on NiCr layered double hydroxide for an improved electrocatalytic oxygen evolution reaction

Abstract

Single atom catalysts (SACs) have shown immense potential in the field of electrocatalysis by effectively modulating the electronic properties of a heterogeneous matrix. Implementation of such cost-effective catalyst systems has become imperative for the facile completion of kinetically sluggish reactions, such as the oxygen evolution reaction (OER). In this study, we report the synthesis of an Ir SAC system stabilized through the surface functionalization of NiCr LDH. With an overpotential of 232 mV and a Tafel slope of 51 mV dec⁻¹, Ir₁/NiCr LDH showed a significant enhancement in the OER performance compared to pristine LDH and the state-of-the-art IrO₂ catalyst. With a Faradaic efficiency of 96.3% and non-depleting OER performance throughout a stability study for 36 h, Ir₁/NiCr LDH exhibited a higher multi-magnitude turnover frequency (TOF) and mass activity compared to IrO₂. Detailed in situ and computational studies illustrated that the suitable binding geometry of Ir sites on the LDH surface and favorable chemical bonding with reactants and intermediates result in enhanced catalytic activity. The atomistic understanding of the subtle influence of SAC coordination on catalytic activities is highly valuable for its strategic design for targeted reactions.