Confining High-Valence Iridium Single Sites onto Nickel Oxyhydroxide for Robust Oxygen Evolution

Abstract

Enhancing activity and stability of iridium-(Ir-) based oxygen evolution reaction (OER) catalysts is of great significance in practice. Here, we report a vacancy-rich nickel hydroxide stabilized Ir single-atom catalyst (Ir 1 −Ni(OH) 2 ), which achieves longterm OER stability over 260 h and much higher mass activity than commercial IrO 2 in alkaline media. In situ X-ray absorption spectroscopy analysis certifies the obvious structure reconstruction of catalyst in OER. As a result, an active structure in which highvalence and peripheral oxygen ligands-rich Ir sites are confined onto the nickel oxyhydroxide surface is formed. In addition, the precise introduction of atomized Ir not only surmounts the large-range dissolution and agglomeration of Ir but also suppresses the dissolution of substrate in OER. Theoretical calculations further account for the activation of Ir single atoms and the promotion of oxygen generation by high-valence Ir, and they reveal that the deprotonation process of adsorbed OH is rate-determining.

Confinement Engineering of Electrocatalyst Surfaces and Interfaces

“…First, the electronic structure of metal centers can be finely controlled to enhance intrinsic activity and thus reduce the usage of noble metals. [58] Second, well-dispersed active sites can be introduced to improve utilization efficiency and promote performance in terms of activity, stability, and selectivity. [59] Along these lines, Song and co-workers prepared highefficiency OER electrocatalysts by confining well-dispersed Ir in Co-based hydroxide nanosheets.…”

“…First, the electronic structure of metal centers can be finely controlled to enhance intrinsic activity and thus reduce the usage of noble metals. [ 58 ] Second, well‐dispersed active sites can be introduced to improve utilization efficiency and promote performance in terms of activity, stability, and selectivity. [ 59 ]…”

Iridium single-atom catalyst coupled with lattice oxygen activated CoNiO2for accelerating the oxygen evolution reaction

“…The above-described variations could be further quantitated by integrating the normalized white-line peak, as shown in Fig. 3d, 10,33 and the average valence states of Ir in Ir SA -V O -CoNiO 2 , Ir SA -CoNiO 2 , IrO 2 , and Ir foil are determined to be +4.74, +4.12, +4, and 0, respectively, conrming the high valence state of Ir x+ (x > 4) in Ir SA -V O -CoNiO 2 , as discussed above. Furthermore, the extended X-ray absorption ne structure spectroscopy (EXAFS) was employed to reveal the character of the atomic coordination conguration of Ir, as shown in Fig.…”

Engineering Single Atom Catalysts for Flow Production: From Catalyst Design to Reactor Understandings

“…SACs may undergo structural reconstruction into the catalytically active form during catalysis (such as the formation of metallic clusters from atomically dispersed copper during CO 2 reduction); they may also prevent reconstruction of the matrix to improve the long-term stability. − Thus, operando techniques such as XAS are useful for direct observation of the dynamic changes in the bond coordination during reaction. ,, In the following studies, we have customized a coin-cell type reactor with double-side Al coating to prevent corrosion of organic solvent and aggressive reactant on the Kapton window, thus allowing the reaction to be followed up to 24 h, which is comparable with the time scale of the experiments. , …”