Pandya Raj, Dorchies Florian, Romanin Davide, Lemineur Jean-François, Kanoufi Frédéric, Gigan Sylvain, Chin Alex W, de Aguiar Hilton B, Grimaud Alexis
Laboratoire Kastler Brossel, ENS-Université PSL, CNRS, Sorbonne Université, Collège de France, 24 rue Lhomond, Paris, France.
Department of Physics, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK.
Nat Commun. 2024 Sep 27;15(1):8362. doi: 10.1038/s41467-024-52536-7.
Transition metal oxides are state-of-the-art materials for catalysing the oxygen evolution reaction (OER), whose slow kinetics currently limit the efficiency of water electrolysis. However, microscale physicochemical heterogeneity between particles, dynamic reactions both in the bulk and at the surface, and an interplay between particle reactivity and electrolyte makes probing the OER challenging. Here, we overcome these limitations by applying state-of-the-art compressive Raman imaging to uncover concurrent bias-dependent pathways for the OER in a dense, crystalline electrocatalyst, α-LiIrO. By spatially and temporally tracking changes in stretching modes we follow catalytic activation and charge accumulation following ion exchange under various electrolytes and cycling conditions, comparing our observations with other crystalline catalysts (IrO, LiCoO). We demonstrate that at low overpotentials the reaction between water and the oxidized catalyst surface is compensated by bulk ion exchange, as usually only found for amorphous, electrolyte permeable, catalysts. At high overpotentials the charge is compensated by surface redox active sites, as in other crystalline catalysts such as IrO. Hence, our work reveals charge compensation can extend beyond the surface in crystalline catalysts. More generally, the results highlight the power of compressive Raman imaging for chemically specific tracking of microscale reaction dynamics in catalysts, battery materials, or memristors.
过渡金属氧化物是催化析氧反应（OER）的先进材料，该反应缓慢的动力学目前限制了水电解的效率。然而，颗粒之间的微观物理化学不均匀性、体相和表面的动态反应以及颗粒反应性与电解质之间的相互作用使得探究OER具有挑战性。在这里，我们通过应用先进的压缩拉曼成像克服了这些限制，以揭示致密晶体电催化剂α-LiIrO 中OER同时存在的偏压依赖性途径。通过在空间和时间上跟踪拉伸模式的变化，我们追踪了在各种电解质和循环条件下离子交换后催化活化和电荷积累的情况，并将我们的观察结果与其他晶体催化剂（IrO₂、LiCoO₂）进行了比较。我们证明，在低过电位下，水与氧化催化剂表面之间的反应由体相离子交换补偿，这通常仅在无定形、电解质可渗透的催化剂中发现。在高过电位下，电荷由表面氧化还原活性位点补偿，如在其他晶体催化剂如IrO₂中一样。因此，我们的工作表明，在晶体催化剂中电荷补偿可以延伸到表面之外。更普遍地说，这些结果突出了压缩拉曼成像在化学特异性跟踪催化剂、电池材料或忆阻器中微观反应动力学方面的强大功能。
