Strain Regulation to Optimize the Acidic Water Oxidation Performance of Atomic‐Layer IrO_x

Abstract

Strain regulation has become an important strategy to tune the surface chemistry and optimize the catalytic performance of nanocatalysts. Herein, the construction of atomic‐layer IrOx on IrCo nanodendrites with tunable IrO bond length by compressive strain effect for oxygen evolution reaction (OER) in acidic environment is demonstrated. Evidenced from in situ extended X‐ray absorption fine structure, it is shown that the compressive strain of the IrOx layer on the IrCo nanodendrites decreases gradually from 2.51% to the unstrained state with atomic layer growth (from ≈2 to ≈9 atomic layers of IrOx), resulting in the variation of the IrO bond length from shortened 1.94 Å to normal 1.99 Å. The ≈3 atomic‐layer IrOx on IrCo nanodendrites with an IrO bond length of 1.96 Å (1.51% strain) exhibits the optimal OER activity compared to the higher‐strained (2.51%, ≈2 atomic‐layer IrOx) and unstrained (>6 atomic‐layer IrOx) counterparts, with an overpotential of only 247 mV to achieve a current density of 10 mA cm−2. Density functional theory calculations reveal that the precisely tuned compressive strain effect balances the adsorbate–substrate interaction and facilitates the rate‐determining step to form HOO*, thus assuring the best performance of the three atomic‐layer IrOx for OER.

Recent Progress in Electrocatalysts for Acidic Water Oxidation

“…[ 131 ] With the addition of Co element, an atomic‐layer IrCo@IrO x ‐3L nanodendrites obtain a very low overpotential of ≈249 mV at 10 mA cm −2 for OER in a 0.05 m H 2 SO 4 solution. [ 132 ] The structure and composition of bimetallic oxides can be modulated by a variety of synthesis methods, including thermal decomposition and sputtering techniques. [ 133,134 ]…”

Electrolyte Effects on the Electrocatalytic Performance of Iridium‐Based Nanoparticles for Oxygen Evolution in Rotating Disc Electrodes

“…Other techniques such as CO stripping, [19,64] hydrogen or mercury under potential deposition (upd), [18,51] estimate the ECSA of the The data presented here is adapted from: r-IrO2 (nanoparticles), [61] Ir-nano 99.8 (nanoparticles), [62] IrO 2 À TiO 2 (nanoparticles), [17] Ir/ATO (nanodendrites), [16] IrNi 0.57 Fe 0.82 /C nanoparticles, [63] IrNiCu/C nanoframes, [64] IrNiO x /C (nanoparticles), [21] CoÀ IrCu ONC/C (nanocages), [19] IrCoNi/C (hollow nanocrystals) [20] IrÀ Ni (9.3) 90.5 (nanowires), [18] and IrCo@Ir-O x -3 L (nanodendrites). [65] The Tafel plots of Ir black nanoparticles correspond to the cyclic voltammograms presented in Figure 2a.…”

Atomic Thickness Catalysts: Synthesis and Applications

“…An atomic layer of IrO x on IrCo was fabricated through a facile electrochemical strategy, enabling the precise regulation of Ir-O bond length to further promote the OER performance. [10] The thickness of IrO x layer could be tuned with different CV cycles in the acid electrolyte and these different IrO x layers were further ascribed to different atomic layers of IrO x . As displayed in Figure 13D,E, IrCo@ IrO x -3L NDs exhibited the optimal OER activity among the samples.…”

“…[1] The commercial IrO 2 / RuO 2 catalysts for oxygen evolution reaction (OER) have some disadvantages in high-cost and longterm-instability. [8][9][10] All in all, as for the CO 2 reduction reaction, current catalysts are largely limited to the low catalytic activity and poor production selectivity, which greatly limit the possible practical applications. [11] Recently, intensive attentions have been paid to the ultrathin nanostructures due to their unique surface-related properties, for instance, high electron mobility, [12,13] quantum Hall effect, [14] and unprecedented optoelectronics.…”

“…[91] More recently, Li's group reported the atomic layer IrO x on IrCo alloys could be well-controlled via a facile electrochemical strategy ( Figure 6E). [10] The bimetallic IrCo nanodendrites (NDs) with a diameter of 3 nm were initially prepared by a solvothermal co-reduction reaction in the OAm and ethylene glycol solvents ( Figure 6F). The HRTEM image of isolated IrCo branch ( Figure 6G) showed that the lattice fringes of IrCo (2.11 Å) was smaller compared with (111) planes of cubic Ir crystal, implying the Co atoms confined into the Ir branch.…”