Alkaline and alkaline-earth iridates have garnered much attention, as they can outperform traditional IrO₂ for oxygen evolution electrocatalysis under acidic conditions. Despite the advantages of their catalytic properties and significant reduction of Ir utilization, dissolution of alkaline and alkaline-earth elements into acid media can be a serious drawback that may confine long-term applications. By using atomic-column-resolved scanning transmission electron microscopy, we demonstrate the surface variations of three alkaline-earth iridates, AIrO₃ (A = Sr or Ba). Directly identifying the structural transformation into metastable nanocrystallites or an amorphous state, we elucidate that substantial surface roughening can be induced by alkaline-earth elemental leaching. In particular, ∼20-fold increases in the active surface area in pseudocubic SrIrO₃ and monoclinic BaIrO₃ are notable structural features. Our findings emphasize both the impact of surface structure on the overall catalytic activity and consequently the important control of chemical leaching to attain a high surface area in iridate-based catalysts.

碱性和碱土金属的铱酸盐引起了广泛的关注，因为它们在酸性条件下的氧气析出电催化性能优于传统的IrO ₂。尽管它们具有催化性能和大大降低Ir利用率的优点，但将碱金属元素和碱土金属元素溶解到酸介质中可能是一个严重的缺点，可能会限制其长期使用。通过使用原子柱分辨扫描透射电子显微镜，我们证明了三种碱土金属铱酸盐A IrO ₃（A = Sr或Ba）。直接鉴定出结构转变为亚稳态纳米晶体或无定形状态，我们阐明了碱土元素浸出可引起大量的表面粗糙。特别是，伪立方SrIrO ₃和单斜晶BaIrO ₃的有效表面积增加了约20倍，这是其显着的结构特征。我们的发现既强调了表面结构对整体催化活性的影响，也强调了化学浸出的重要控制，以实现基于铱酸盐的催化剂的高表面积。