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

Abstract

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 β-NiOOH(001) surface enhanced the electric conductivity while also activating an oxygen site involving three Ni atoms (Ni3 site) to realize a remarkably low OER overpotential of only η = 0.46 V, much lower than the overpotential on the oxygen site involving Ir + two Ni atoms (IrNi2 site, η = 0.77 V) or the oxygen site involving three Ni atoms in pristine β-NiOOH (η = 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.

Strategies for designing more efficient electrocatalysts towards the urea oxidation reaction

“…Noble metal-based materials are the state-of-the-art electrocatalysts for some important electrocatalytic reactions, such as Pt for the oxygen reduction reaction (ORR) and the HER and RuO 2 and IrO 2 for the OER. 34–40 However, for the UOR, noble metal-based electrocatalysts only show inferior performance, let alone their high costs and scarcity. 41 Fortunately, G. Botte and co-workers demonstrated that nickel exhibited much better UOR performance than some noble metals (Pt, Pt–Ir, and Rh) in an alkaline environment in 2009.…”

Epitaxially Grown Heterostructured SrMn3O6−x‐SrMnO3 with High‐Valence Mn3+/4+ for Improved Oxygen Reduction Catalysis

“…Thee lectron transfer number (n)o fS MO x -SMO (3.88) was comparable to Pt/C (3.92), which suggested anear-ideal ORR process involving afour-electron reduction pathway.Further,the epitaxially grown SMO x -SMO with Mn-O-Mn interfacial bonding offered better ORR stability than the unbonded heterojunctions (Figure S10). [25] In Figure 3f, SMO x -SMO/CNTs maintained 90 %o ft he initial current after 25 ha ta noperating voltage of 0.2 V( cf.P t/C,7 0% of initial current after 25 h). Furthermore,t he morphology and chemical composition of the material did not change significantly after the stability test (Figure S11).…”

Shining Light on Anion-Mixed Nanocatalysts for Efficient Water Electrolysis: Fundamentals, Progress, and Perspectives

“…To gain deeper insights into the role of metal dopants in enhancing (oxy)hydroxides’ OER activity, Ir-doped Ni(OH) 2 nanosheets were 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 IrO 2 catalyst [ 196 ]. The DFT calculations with Hubbard U correction indicated that Ir doping increased the conductivity of β-NiOOH(001) and activated the oxygen site containing 3 Ni atoms (Ni 3 site).…”