Structural and Electronic Engineering of Ir-Doped Ni-(Oxy)hydroxide Nanosheets for Enhanced Oxygen Evolution Activity

Discovering highly active and stable electrocatalysts for the oxygen evolution reaction (OER) is critical to the commercial development of many next-generation energy conversion and storage devices, with Fe-doped nickel (oxy)hydroxide representing one of the most promising OER catalysts developed to date. However, the active sites and mechanism of OER on Fe-doped nickel (oxy)hydroxide catalysts remain unclear. To gain deeper insights into the role of metal dopants in enhancing OER activity, we explored here the role of Ir-doping in the OER performance of nickel (oxy)hydroxide catalysts, placing particular emphasis on the nature of the active site. Density functional theory calculations with Hubbard U correction revealed that Ir-doping of a beta-NiOOH(001) surface enhanced the electric conductivity while also activating an oxygen site involving three Ni atoms (Ni-3 site) to realize a remarkably low OER overpotential of only eta = 0.46 V, much lower than the overpotential on the oxygen site involving Ir + two Ni atoms (IrNi2 site, eta = 0.77 V) or the oxygen site involving three Ni atoms in pristine beta-NiOOH (eta = 0.66 V). Guided by the computational results, ultrathin Ir-doped Ni(OH)(2) nanosheets were then fabricated through a combination of hydrothermal assembly and liquid exfoliation, with the nanosheets transforming to Ir-doped NiOOH during OER and offering superior activity relative to pristine Ni(OH)(2) nanosheets or a commercial IrO2 catalyst, thereby validating the theoretical predictions. The computational and experimental results thus conclusively demonstrate that Ir-doping and nanosheet engineering are synergistic strategies for tuning the electronic and structural properties of nickel (oxy)hydroxides for improved oxygen evolution electrocatalysis.

Automated summary

The study reveals that Ir doping significantly enhances the OER activity of nickel (oxy)hydroxide, surpassing a commercial IrO2 catalyst. Computational and experimental validation confirm that Ir doping and nanosheet engineering are effective strategies for tuning the electronic and structural properties of nickel (oxy)hydroxides for improved oxygen evolution electrocatalysis.