The in situ etching assisted synthesis of Pt-Fe-Mn ternary alloys with high-index facets as efficient catalysts for electro-oxidation reactions
The in situ etching assisted synthesis of Pt-Fe-Mn ternary alloys with high-index facets as efficient catalysts for electro-oxidation reactions
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原位刻蚀辅助合成高折射率晶面Pt-Fe-Mn三元合金作为电氧化反应的高效催化剂
DOI：
10.1039/c8nr10231g
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发表时间：
2019
期刊：
影响因子：
6.7
通讯作者：
Sun Shi Gang
中科院分区：
文献类型：
--
作者：
Qin Congli;Fan Aixin;Zhang Xin;Dai Xiaoping;Sun Hui;Ren Danhua;Dong Zhun;Wang Yao;Luan Chenglong;Ye Jin Yu;Sun Shi Gang
在电催化反应中，具有高折射率晶面的铂基合金比具有低折射率晶面的铂基合金具有更高的比催化活性。然而，特定Pt表面的暴露将需要良好限定的纳米结构，其通常只能在较大尺寸下获得。因此，Pt原子在具有HIF的Pt基合金中的低分散度将影响Pt的原子利用率，导致这些Pt基合金中的大多数表现出比商业Pt/C和Pt黑催化剂更低的质量活性用于电催化反应。在此，我们提出了一种新的策略，通过原位蚀刻Pt-Fe-Mn凹立方体（CNC），同时保持Pt-Fe-Mn合金的形貌，以提高Pt原子的利用率，从而提高质量活性，将较大尺寸的纳米晶体的表面积分成小的表面积纳米晶体。值得注意的是，Pt-Fe-Mn独特凹立方体（UCNC）纳米晶体（NC）对甲醇氧化反应（莫尔）显示出比Pt-Fe-Mn CNC、商业Pt黑和Pt/C高得多的比活性和质量活性。Tafel动力学分析表明，UCNC Pt-Fe-Mn NCs在全电位下的Tafel斜率最小，在高电位（高于0.45 V）下，CH 3OH分子的第一个C-H键的断裂和第一次电子转移是速率控制步骤。分子水平上的原位傅里叶变换红外反射（FTIR）光谱研究表明，甲醇化学吸收发生在UCNC NC电极的-0.2 V低电位下。同时，在UCNC NC电极上观察到更高的CO2产率，表明UCNC Pt-Fe-Mn NC在甲醇电氧化过程中具有较强的抗中毒能力。此外，在甲酸氧化（FAOR）测试中，Pt-Fe-Mn UCNC NC的活性和长期耐久性也被发现优于Pt-Fe-Mn CNC、商业Pt黑和Pt/C的那些上级。在莫尔和FAOR中增强的催化性能最可能是由于由小尺寸颗粒组成的独特HIF结构、增强的Pt利用率、晶体缺陷的丰富性以及Pt、Fe和Mn金属的协同效应。本文的工作为合理设计铂基合金与高强度介电层以提高电催化反应的催化性能提供了理论依据。
Pt-Based alloys enclosed with high-index facets (HIFs) generally show much higher specific catalytic activities than their counterparts with low-index facets in electro-catalytic reactions. However, the exposure of a certain Pt surface would require a well-defined nanostructure, which usually can only be obtained at larger sizes. Therefore, a low dispersion of Pt atoms in Pt-based alloys with HIFs would affect the atomic utilization of Pt, resulting in most of these Pt-based alloys exhibiting lower mass activity than commercial Pt/C and Pt black catalysts for electro-catalytic reactions. Herein, we address a novel strategy to divide the surface areas of larger sized nanocrystals into small surface area nanocrystals by in situ etching Pt–Fe–Mn concave cubes (CNCs) while maintaining the morphology of the Pt–Fe–Mn alloys to improve the utilization of Pt atoms and thus increase the mass activity. Remarkably, the Pt–Fe–Mn unique concave cube (UCNC) nanocrystals (NCs) showed much higher specific and mass activities toward the methanol oxidation reaction (MOR) than the Pt–Fe–Mn CNCs, commercial Pt black and Pt/C. The kinetic analysis from Tafel plots indicated that UCNC Pt–Fe–Mn NCs had the lowest Tafel slope at whole potentials and the splitting of the first C–H bond of a CH3OH molecule with the first electron transfer was the rate-determining step at high potentials (above 0.45 V). In situ Fourier transform infrared reflection (FTIR) spectroscopic investigation at the molecular level indicated that methanol chemical absorption took place at a low potential of −0.2 V at the UCNC NC electrode. Meanwhile, much higher CO2 productivity was observed at the UCNC NC electrode, indicating the strong anti-poisoning ability of the UCNC Pt–Fe–Mn NCs during methanol electrooxidation. Furthermore, in the formic acid oxidation (FAOR) test, the activity and long-term durability of the Pt–Fe–Mn UCNC NCs were also found to be superior to those of the Pt–Fe–Mn CNCs, commercial Pt black and Pt/C. The enhanced catalytic performance in both the MOR and FAOR is most probably due to the unique HIF structure consisting of small sized particles, enhanced Pt utilization, the richness of crystalline defects and synergetic effects of Pt, Fe, and Mn metals. Our present work provides an insight into the rational design of Pt based alloys with HIFs to improve the catalytic performance of electro-catalytic reactions for fundamental study.