School of Mechanical and Power Engineering , East China University of Science and Technology , Shanghai 200237 , China.
Department of Chemical and Biological Engineering , University at Buffalo, The State University of New York , Buffalo , New York 14260 , United States.
Nano Lett. 2018 Jul 11;18(7):4163-4171. doi: 10.1021/acs.nanolett.8b00978. Epub 2018 Jun 11.
Highly ordered Pt alloy structures are proven effective to improve their catalytic activity and stability for the oxygen reduction reaction (ORR) for proton exchange membrane fuel cells. Here, we report a new approach to preparing ordered PtCo intermetallic nanoparticles through a facile thermal treatment of Pt nanoparticles supported on Co-doped metal-organic-framework (MOF)-derived carbon. In particular, the atomically dispersed Co sites, which are originally embedded into MOF-derived carbon, diffuse into Pt nanocrystals and form ordered PtCo structures. It is very crucial for the formation of the ordered PtCo to carefully control the doping content of Co into the MOFs and the heating temperatures for Co diffusion. The optimal PtCo nanoparticle catalyst has achieved significantly enhanced activity and stability, exhibiting a half-wave potential up to 0.92 V vs reversible hydrogen electrode (RHE) and only losing 12 mV after 30 000 potential cycling between 0.6 and 1.0 V. The highly ordered intermetallic structure was retained after the accelerated stress tests made evident by atomic-scale elemental mapping. Fuel cell tests further verified the high intrinsic activity of the ordered PtCo catalysts. Unlike the direct use of MOF-derived carbon supports for depositing Pt, we utilized MOF-derived carbon containing atomically dispersed Co sites as Co sources to prepare ordered PtCo intermetallic catalysts. The new synthesis approach provides an effective strategy to develop active and stable Pt alloy catalysts by leveraging the unique properties of MOFs such as 3D structures, high surface areas, and controlled nitrogen and transition metal dopings.
高度有序的 Pt 合金结构已被证明可有效提高其对于质子交换膜燃料电池的氧还原反应（ORR）的催化活性和稳定性。在此，我们报告了一种通过简单的热处理策略来制备有序 PtCo 金属间化合物纳米颗粒的新方法，该策略使用负载在 Co 掺杂的金属-有机骨架（MOF）衍生碳上的 Pt 纳米颗粒。具体而言，原本嵌入 MOF 衍生碳中的原子分散的 Co 位点会扩散到 Pt 纳米晶中并形成有序的 PtCo 结构。对于形成有序 PtCo 结构，仔细控制 Co 掺杂到 MOF 中的含量和 Co 扩散的加热温度是非常关键的。最优的 PtCo 纳米颗粒催化剂表现出显著增强的活性和稳定性，其半波电势高达 0.92 V 相对于可逆氢电极（RHE），并且在 0.6 到 1.0 V 之间进行 30000 次电位循环后仅损失 12 mV。通过原子尺度的元素映射可以明显看出，高度有序的金属间结构在加速压力测试后得以保留。燃料电池测试进一步验证了有序 PtCo 催化剂的高本征活性。与直接使用 MOF 衍生碳载体来沉积 Pt 不同，我们利用含有原子分散 Co 位点的 MOF 衍生碳作为 Co 源来制备有序 PtCo 金属间化合物催化剂。这种新的合成方法为通过利用 MOF 的独特性质（如 3D 结构、高比表面积以及可控的氮和过渡金属掺杂）来开发活性和稳定的 Pt 合金催化剂提供了有效的策略。
