Spin-related symmetry breaking induced by half-disordered hybridization in BixEr2-xRu2O7 pyrochlores for acidic oxygen evolution

Abstract

While acidic oxygen evolution reaction plays a critical role in electrochemical energy conversion devices, the sluggish reaction kinetics and poor stability in acidic electrolyte challenges materials development. Unlike traditional nano-structuring approaches, this work focuses on the structural symmetry breaking to rearrange spin electron occupation and optimize spin-dependent orbital interaction to alter charge transfer between catalysts and reactants. Herein, we propose an atomic half-disordering strategy in multistage-hybridized BixEr2-xRu2O7 pyrochlores to reconfigure orbital degeneracy and spin-related electron occupation. This strategy involves controlling the bonding interaction of Bi-6s lone pair electrons, in which partial atom rearrangement makes the active sites transform into asymmetric high-spin states from symmetric low-spin states. As a result, the half-disordered BixEr2-xRu2O7 pyrochlores demonstrate an overpotential of ~0.18 V at 10 mA cm−2 accompanied with excellent stability of 100 h in acidic electrolyte. Our findings not only provide a strategy for designing atom-disorder-related catalysts, but also provides a deeper understanding of the spin-related acidic oxygen evolution reaction kinetics.

Acidic oxygen evolution reaction: Mechanism, catalyst classification, and enhancement strategies

“…[ 120 ] Copyright 2020, John Wiley and Sons; (I) Ru‐4d orbital splitting for different symmetry; (J) LSV curves for OER of Bi x Er 2 − x Ru 2 O 7 and control samples; Reproduced with permission. [ 121 ] Copyright 2022, Springer Nature; (K) Lattice structures of Y 2 [Ru 1.6 Y 0.4 ]O 7– δ and Y 2 Ru 2 O 7 ; (L) OER performance of Y 2 [Ru 1.6 Y 0.4 ]O 7– δ and control samples. Reproduced with permission.…”

“…Similar to perovskites, the highly tunable and flexible A‐ and B‐sites allow the physicochemical properties of pyrochlore oxides to be easily engineered. For example, Liu et al [ 121 ] modulated the A‐site component to construct Bi x Er 2− x Ru 2 O 7 pyrochlores with a unique spintronic configuration. The bonding between Ru and O was affected by Bi‐6s lone pair electrons, which led to the disordered atomic hybridization of Bi 2 Ru 2 O 7 at room temperature.…”

“…[120] Copyright 2020, John Wiley and Sons; (I) Ru-4d orbital splitting for different symmetry; (J) LSV curves for OER of Bi x Er 2 − x Ru 2 O 7 and control samples; Reproduced with permission. [121] Copyright 2022, Springer Nature; [122] Copyright 2020, John Wiley and Sons. OER, oxygen evolution reaction.…”

Oxygen Evolution Electrocatalysts for the Proton Exchange Membrane Electrolyzer: Challenges on Stability

“…Coordination effect Bi 1.5 Er 0.5 Ru 2 O 7 [161] 51.3 180 0.024 s −1 @ 1.43 V 238 A g −1 @ 1.5 V 10 mA cm −2 for 100 h Y 2 Ru 1.2 Ir 0.8 O 7 [162] 47.56 220 10 mA cm −2 for 2000 h AD-HN-Ir [28] 0.0035 Ir 39 216 1.42 s −1 @ 1.446 V 2860 A g −1 metal @ 1.446 V 10 mA cm −2 for 100 h Co 2 MnO 4 [33] 10 79.6 400 200 mA cm −2 for 1500 h MEO-GP [88] 346 270 20 mA cm −2 for 320 h Strain s-RuO 2 /ATO [102] 0.19 Ru 50 198 10 mA cm −2 for 150 h hierarchical Pd [96] 51.3 196 407.2 A g −1 @ 1.53 V 10 mA cm −2 for 500 h Ta 0.1 Tm 0.1 Ir 0.8 O 2-δ [92] 0.04 64 198 3126 A g −1 Ir @ 1.496 V 10 mA cm −2 for 500 h phase & facet 3R-IrO 2 limited to the traditional three-electrode system, and only a few electrocatalysts with non-noble/less noble metal demonstrate the feasibility in the PEM electrolyzer (Figure 1b, with the detailed performance summarized in Table 2), which is still rather insufficient compared to the much more complex working conditions in the industrial scale.…”

Iridium-based Electrocatalysts for Acidic Oxygen Evolution Reaction: Engineering Strategies to Enhance the Activity and Stability

“…Iridium-based catalysts (IBCs) represent one of the most promising classes of OER catalysts due to their great intrinsic stability in acidic media. Thus, a number of innovative approaches to synthesizing IBCs have been developed in the past few years, such as molten salt method, 7,8 pulsed laser, 9 selenic acid etching, 10 wet chemistry method, 11 solution combustion synthesis method, 12 ammonia induction method, 13 sol-gel route, 14 template method, 15 etc., which will be summarized in the third part of this review. Several excellent reviews on elucidating the mechanisms of the oxygen evolution reaction have been published, mainly focused on the adsorption evolution mechanism (AEM), lattice oxygen evolution mechanism (LOM), and the degradation mechanism of catalysts.…”