Effective Strain Engineering of IrO₂ Toward Improved Oxygen Evolution Catalysis through a Catalyst‐Support System

Abstract

A template‐free, one‐step synthesis of nano‐IrO2 on a layered Mn−Co birnessite support was developed to induce the catalyst‐support interaction. The IrO2 nanoparticles were prepared with inherent crystal lattice strain, which is derived from the Ir‐O−Mn mismatch at the interface. The oxidation state of iridium is higher than IrIV, revealing the electron transfer to the substrate. On account of the crystal lattice distortion and electronic manipulations being favorable to the oxygen evolution reaction (OER), the as‐synthesized composite exhibited excellent OER activity and stability. The improved catalytic nature was followed by enhancement in the electrochemical active surface area, mass specific activity, and intrinsic activity. Moreover, the Tafel slope of 42 mV dec−1 reveals better reaction kinetics for IrO2/Mn−Co (2 : 1)‐birnessite than many previously reported catalysts despite the low precious noble metal content in the as‐synthesized composite. Conclusively, we have proven that the strain engineering holds vital importance in forming catalyst‐support interaction and rational design of catalysts.

Influence of the MnO2 Phase on Oxygen Evolution Reaction Performance for Low‐Loading Iridium Electrocatalysts

“…While the Ir4f 5/2 binding energy showed the same trend. The binding energy shifted towards higher one, revealing that the samples had a higher oxidation state of iridium [6] . The Ir−O bond distance is highly sensitive to the iridium oxidation state [9,26] .…”

“…The binding energy shifted towards higher one, revealing that the samples had a higher oxidation state of iridium. [6] The IrÀ O bond distance is highly sensitive to the iridium oxidation state. [9,26] The IrÀ O bond length in IrO x would decrease as the average valence of iridium increases.…”

“…Two general approaches have been used for this purpose. One approach is to alloy with some transition metals such as IrCo, [6] IrFe [7] and IrNi [8] . The other one is to synthesize the supported iridium catalysts such as IrO 2 /TiO 2 [9] and IrO 2 /Co 3 O 4 [10] .…”

“…al [12b] loaded Co onto MnO 2 support to obtain a cost‐effective OER catalyst, which had low transfer resistance and high current density. Some researchers have also investigated the electrocatalytic performance of Mn oxides in acidic media [1a,6,12c, 15] . To decrease the overpotential and reduce the usage of noble metal, the ruthenium or iridium dioxide combined with manganese dioxide were developed [1a,15b] .…”

Activity and Stability of Oxides During Oxygen Evolution Reaction‐‐‐From Mechanistic Controversies Toward Relevant Electrocatalytic Descriptors

“…Further, a reasonable strategy to modify the OER activity of catalysts and avoid scaling relations is doping with cations that can activate proton donor-acceptor functionality on the conventionally inactive bridge surface sites (Halck et al, 2014). Probably the most popular approach today to tune catalyst activity is to introduce strain in the oxide lattice using a component(s) that can be easily leached out (Yao et al, 2019) or by interaction with the support (Zhou et al, 2019). Importantly, lattice strain has as a consequence a geometric effect in the form of lattice distortion and chemical effect in the form of change in oxygen nonstoichiometry (Wang et al, 2019).…”