<i>In My Element</i>: Iridium

Armaroli, Nicola

doi:10.1002/chem.201804692

Cited by 3 publications

(1 citation statement)

References 4 publications

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“…[ 7 ] Although the acidic OER activities of Ru based materials are higher than those of Ir‐based materials, their acidic OER stability is lower than that of Ir‐based materials due to the high solubility of higher valence state Ru in water. However, the content of iridium on earth is very low [ 8 ] and its OER activity has much room for improvement. [ 9 ] All these challenges require the development of the rational design of Ir‐based OER catalysts.…”

Section: Introductionmentioning

confidence: 99%

Two Dimensional Ir‐Based Catalysts for Acidic OER

Jia

Shao

2023

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Electrochemical water splitting in acidic media is one of the most promising hydrogen production technologies, yet its practical applications in proton exchange membrane (PEM) water electrolyzers are limited by the anodic oxygen evolution reaction (OER). Iridium (Ir)‐based materials are considered as the state‐of‐the‐art catalysts for acidic OER due to their good stability under harsh acidic conditions. However, their activities still have much room for improvement. Two‐dimensional (2D) materials are full of the advantages of high‐surface area, unique electrical properties, facile surface modification, and good stability, making the development of 2D Ir‐based catalysts more attractive for achieving high catalytic performance. In this review, first, the unique advantages of 2D catalysts for electrocatalysis are reviewed. Thereafter, the classification, synthesis methods, and recent OER achievements of 2D Ir‐based materials, including pure metals, alloys, oxides, and perovskites are introduced. Finally, the prospects and challenges of developing 2D Ir‐based catalysts for future acidic OER are discussed.

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Section: Introductionmentioning

confidence: 99%

Two Dimensional Ir‐Based Catalysts for Acidic OER

Jia

Shao

2023

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Progress of Ir/Ru-based catalysts for electrocatalytic oxygen evolution reaction in acidic environments

Li,

Tang,

Zhou

et al. 2024

International Journal of Hydrogen Energy

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Excited-State Engineering in Heteroleptic Ionic Iridium(III) Complexes

et al. 2021

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Conspectus Iridium(III) complexes have assumed a prominent role in the areas of photochemistry and photophysics due to the peculiar properties of both the metal itself and the ligand environment that can be assembled around it. Ir(III) is larger, heavier, and bears a higher ionic charge than its analogue and widely used d6 ions such as Fe(II) and Ru(II). Accordingly, its complexes exhibit wider ligand-field d–d orbital splitting with electronic levels centered on the metal, typically nonemissive and photodissociative, not playing a relevant role in excited-state deactivations. In other words, iridium complexes are typically more stable and/or more emissive than Fe(II) and Ru(II) systems. Additionally, the particularly strong heavy-atom effect of iridium promotes singlet–triplet transitions, with characteristic absorption features in the UV–vis and relatively short excited-state lifetimes of emissive triplet levels. Ir(III) is also a platform for anchoring ligands of rather different sorts. Its versatile chemistry includes not only coordination with classic N∧N neutral ligands but also the binding of negatively charged chelators, typically having a cyclometalating C∧N anchor. The carbon–metal bond in these systems has some degree of covalent character, but this does not preclude a localized description of the excited states of the related complexes, which can be designated as metal-centered (MC), ligand-centered (LC), or charge transfer (CT), allowing a simplified description of electronic and photophysical properties. The possibility of binding different types of ligands and making heteroleptic complexes is a formidable tool for finely tuning the nature and energy of the lowest electronic excited state of cationic Ir(III) complexes by ligand design. Herein we give an account of our work on several families of iridium complexes typically equipped with two cyclometalating bidentate ligands (C∧N), in combination with mono or bidentate “ancillary” ligands with N∧N, C∧N, and C∧C motifs. We have explored new synthesis routes for both cyclometalating and ancillary ligands, obtaining primarily cationic complexes but also some neutral or even negatively charged systems. In the domain of the ancillary ligands, we have explored isocyanides, carbenes, mesoionic triazolylidenes, and bis-tetrazolic ligands. For the cyclometalating moiety, we have investigated carbene, mesoionic triazolylidene, and tetrazolic systems. Key results of our work include new strategies to modify both cyclometalating and ancillary ligands by relocating ionic charges, the determination of new factors affecting the stability of complexes, a demonstration of subtle structural effects that strongly modify the photophysical properties, new options to get blue-greenish emitters for optoelectronic devices, and a set of ligand modifications allowing the optimization of electrochemical and excited-state properties to obtain new promising Ir(III) complexes for photoredox catalysis. These results constitute a step forward in the preparation of custom i...

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In My Element: Iridium

Abstract: The In My Element series celebrates the personal accounts from Chemistry – A European Journal Editorial Board members for the 2019 International Year of the Periodic Table. In this contribution, Nicola Armaroli gives his story on iridium.

Cited by 3 publications

References 4 publications

Two Dimensional Ir‐Based Catalysts for Acidic OER

Two Dimensional Ir‐Based Catalysts for Acidic OER

Progress of Ir/Ru-based catalysts for electrocatalytic oxygen evolution reaction in acidic environments

Excited-State Engineering in Heteroleptic Ionic Iridium(III) Complexes

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