Samira Samji, Hong Jiyun, Camayang John Carl A, Sun Kai, Hoffman Adam S, Bare Simon R, Nikolla Eranda
Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States.
Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
JACS Au. 2021 Nov 5;1(12):2224-2241. doi: 10.1021/jacsau.1c00359. eCollection 2021 Dec 27.
Compositionally versatile, nonstoichiometric, mixed ionic-electronic conducting metal oxides of the form A B O ( = 1 → ∞; A = rare-earth-/alkaline-earth-metal cation; B = transition-metal (TM) cation) remain a highly attractive class of electrocatalysts for catalyzing the energy-intensive oxygen evolution reaction (OER). The current design strategies for describing their OER activities are largely derived assuming a static, unchanged view of their surfaces, despite reports of dynamic structural changes to 3d TM-based perovskites during OER. Herein, through variations in the A- and B-site compositions of A B O oxides ( = 1 (ABO) or = ∞ (ABO); A = La, Sr, Ca; B = Mn, Fe, Co, Ni), we show that, in the absence of electrolyte impurities, surface restructuring is universally the source of high OER activity in these oxides and is dependent on the initial oxide composition. Oxide surface restructuring is induced by irreversible A-site cation dissolution, resulting in formation of a TM oxyhydroxide shell on top of the parent oxide core that serves as the active surface for OER. The rate of surface restructuring is found to depend on (i) composition of A-site cations, with alkaline-earth-metal cations dominating lanthanide cation dissolution, (ii) oxide crystal phase, with = 1 ABO oxides exhibiting higher rates of A-site dissolution in comparison to = ∞ ABO perovskites, (iii) lattice strain in the oxide induced by mixed rare-earth- and alkaline-earth-metal cations in the A-site, and (iv) oxide reducibility. Among the generated 3d TM oxyhydroxide structures from A B O oxides, Co-based structures are characterized by superior OER activity and stability, even in comparison to as-synthesized Co-oxyhydroxide, pointing to the generation of high active surface area structures through oxide restructuring. These insights are critical toward the development of revised design criteria to include surface dynamics for effectively describing the OER activity of nonstoichiometric mixed-metal oxides.
具有通式(A_{x}B_{y}O_{z})（(z = 1 → ∞)；(A =)稀土/碱土金属阳离子；(B =)过渡金属（TM）阳离子）的成分多样、非化学计量的混合离子 - 电子传导金属氧化物，仍然是用于催化耗能析氧反应（OER）的一类极具吸引力的电催化剂。尽管有报道称基于3d TM的钙钛矿在OER过程中会发生动态结构变化，但目前用于描述其OER活性的设计策略很大程度上是在假设其表面静态不变的情况下得出的。在此，通过改变(A_{x}B_{y}O_{z})氧化物（(z = 1)（ABO）或(z = ∞)（ABO）；(A = La)、(Sr)、(Ca)；(B = Mn)、(Fe)、(Co)、(Ni)）的A位和B位组成，我们表明，在不存在电解质杂质的情况下，表面重构普遍是这些氧化物中高OER活性的来源，并且取决于初始氧化物组成。氧化物表面重构是由不可逆的A位阳离子溶解引起的，导致在母体氧化物核顶部形成一层TM羟基氧化物壳，该壳作为OER的活性表面。发现表面重构速率取决于：（i）A位阳离子的组成，碱土金属阳离子主导镧系阳离子的溶解；（ii）氧化物晶相，与(z = ∞)的ABO钙钛矿相比，(z = 1)的ABO氧化物表现出更高的A位溶解速率；（iii）由A位中混合的稀土和碱土金属阳离子引起的氧化物晶格应变；以及（iv）氧化物的还原性。在由(A_{x}B_{y}O_{z})氧化物生成的3d TM羟基氧化物结构中，基于Co的结构具有优异的OER活性和稳定性，甚至与合成的羟基氧化钴相比也是如此，这表明通过氧化物重构生成了高活性表面积结构。这些见解对于制定修订的设计标准至关重要，该标准应包括表面动力学，以有效描述非化学计量混合金属氧化物的OER活性。
Zotero 插件
