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The Role of Phosphate Functionalization on the Oxygen Evolution Reaction Activity of Cobalt-Based Oxides at Different pH Values
Small Structures ( IF 13.9 ) Pub Date : 2023-08-31 , DOI: 10.1002/sstr.202300106
Wataru Yoshimune 1 , Juliana B. Falqueto 1 , Adam H. Clark 1 , Nur Sena Yüzbasi 2 , Thomas Graule 2 , Dominika Baster 1 , Mario El Kazzi 1 , Thomas J. Schmidt 1, 3 , Emiliana Fabbri 1
Affiliation  

Cobalt-based oxides have attracted attention as active electrocatalysts for the oxygen evolution reaction (OER) in alkaline electrolytes. However, highly OER active catalysts at near-neutral pHs are also desired for practical applications. Herein, a dry phosphate functionalization process is presented to enhance the OER activity of different cobalt-based catalysts at near-neutral pHs. Electrochemical evaluations show that the P-functionalization can effectively improve the OER activity at near-neutral pHs for La0.2Sr0.8CoO3–δ , La0.2Sr0.8Co0.8Fe0.2O3–δ , and CoO x catalysts, but not for La0.5Sr1.5CoO4–δ . Bulk and surface sensitive X-ray absorption spectroscopy and X-ray photoelectron spectroscopy unveil the influence of P incorporated in the order of ppm on the electronic state, local structure, and surface composition of the investigated catalysts. The P-functionalization reduces the Co oxidation state in La0.2Sr0.8CoO3–δ and La0.5Sr1.5CoO4–δ , but the latter also presents significant Sr-based segregations on the surface-inhibiting OER activity at near-neutral pHs. Differently, La0.2Sr0.8CoO3–δ , and to a lesser extent La0.2Sr0.8Co0.8Fe0.2O3–δ and CoO x , shows improved OER activity at neutral pH after the P-functionalization. The findings disclose that P-functionalization successfully enhances OER activity at near-neutral pHs and that both phosphate ion assistance in the OER mechanism and catalyst Co oxidation state can play a role in the enhanced OER activity.

中文翻译:

磷酸盐功能化对不同pH值下钴基氧化物析氧反应活性的影响

钴基氧化物作为碱性电解质中析氧反应(OER)的活性电催化剂而引起人们的关注。然而,实际应用中还需要在接近中性 pH 值下具有高 OER 活性的催化剂。在此,提出了一种干磷酸盐官能化工艺,以增强不同钴基催化剂在接近中性 pH 条件下的 OER 活性。电化学评估表明,P-功能化可以有效提高La 0.2 Sr 0.8 CoO 3– δ 、La 0.2 Sr 0.8 Co 0.8 Fe 0.2 O 3– δ 和CoO x催化剂在近中性pH下的OER活性,但不能La 0.5 Sr 1.5 CoO 4– δ。体相和表面敏感 X 射线吸收光谱和 X 射线光电子能谱揭示了 ppm 量级的 P 掺入对所研究催化剂的电子态、局域结构和表面组成的影响。P-官能化降低了 La 0.2 Sr 0.8 CoO 3– δ和 La 0.5 Sr 1.5 CoO 4– δ中的 Co 氧化态,但后者在接近中性 pH 条件下的表面抑制 OER 活性上也呈现出显着的基于 Sr 的偏析。 。不同的是,La 0.2 Sr 0.8 CoO 3– δ以及较小程度的 La 0.2 Sr 0.8 Co 0.8 Fe 0.2 O 3–δ和 CoO x,在 P 官能化后在中性 pH 下表现出改善的 OER 活性。研究结果表明,P-功能化成功地增强了接近中性 pH 条件下的 OER 活性,并且 OER 机制中的磷酸根离子辅助和催化剂 Co 氧化态都可以在增强 OER 活性中发挥作用。
更新日期:2023-08-31
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