Improved Hydrogen Oxidation Reaction Activity and Stability of Buried Metal-Oxide Electrocatalyst Interfaces,Chemistry of Materials

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Improved Hydrogen Oxidation Reaction Activity and Stability of Buried Metal-Oxide Electrocatalyst Interfaces
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-08-18 , DOI: 10.1021/acs.chemmater.0c02048
Florian D. Speck _{1,

2} , Farhan S. M. Ali ₃ , Michael T. Y. Paul ₁ , Ramesh K. Singh _{4,

5} , Thomas Böhm _{1,

2} , André Hofer ₆ , Olga Kasian ₇ , Simon Thiele _{1,

2} , Julien Bachmann _{6,

8} , Dario R. Dekel _{4,

5} , Tanja Kallio ₃ , Serhiy Cherevko ₁

Affiliation

Various bifunctional metal-oxide composites have recently been proposed as advanced hydrogen oxidation reaction (HOR) electrocatalysts for anion-exchange membrane fuel cells (AEMFCs). It is postulated that metal and oxide are active sites for the adsorption of hydrogen/proton and hydroxide ions, respectively. Of particular interest are the so-called buried interfaces. To investigate processes governing activity and stability at such interfaces, we prepare model Pd and Pt electrocatalysts which are fully covered by thin CeO_x films. We investigate how oxide thickness influences HOR activity and dissolution stability of the electrocatalysts. It is found that materials behave very differently and that only Pd exhibits an enhanced HOR activity, while both oxide-protected metals are more stable toward dissolution. A 10-fold decrease in dissolution and 15-fold increase in HOR exchange current density are demonstrated for the optimized Pd/CeO_x composites in comparison to pure Pd. We assess the mechanism of the electrocatalytic improvement as well as the role of the protective oxide films in such systems through advanced electrochemical and physical analysis. It is highlighted that a uniform, semipermeable oxide layer with a maximized electrocatalyst–oxide interface is crucial to form HOR catalysts with improved activity and stability.

中文翻译：

改进的氢氧化反应活性和埋入式金属氧化物电催化剂界面的稳定性

最近已经提出了各种双功能金属氧化物复合物作为用于阴离子交换膜燃料电池（AEMFC）的高级氢氧化反应（HOR）电催化剂。假定金属和氧化物分别是用于吸附氢/质子和氢氧根离子的活性位点。特别令人感兴趣的是所谓的掩埋接口。为了研究控制此类界面上的活性和稳定性的过程，我们准备了被薄CeO _x完全覆盖的Pd和Pt模型电催化剂电影。我们研究了氧化物厚度如何影响HOR活性和电催化剂的溶解稳定性。发现材料的行为非常不同，并且只有Pd表现出增强的HOR活性，而两种氧化物保护的金属对溶解都更稳定。与纯Pd相比，优化的Pd / CeO _x复合材料的溶解度降低了10倍，HOR交换电流密度提高了15倍。通过先进的电化学和物理分析，我们评估了电催化改进的机理以及保护性氧化膜在此类系统中的作用。需要强调的是，具有最大化电催化剂-氧化物界面的均匀，半渗透性氧化物层对于形成活性和稳定性得到改善的HOR催化剂至关重要。

更新日期：2020-09-22

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