Gatalo Matija, Bonastre Alejandro Martinez, Moriau Léonard Jean, Burdett Harriet, Ruiz-Zepeda Francisco, Hughes Edwin, Hodgkinson Adam, Šala Martin, Pavko Luka, Bele Marjan, Hodnik Nejc, Sharman Jonathan, Gaberšček Miran
Department of Materials Chemistry, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
ReCatalyst d.o.o., Hajdrihova 19, 1000 Ljubljana, Slovenia.
ACS Appl Energy Mater. 2022 Jul 25;5(7):8862-8877. doi: 10.1021/acsaem.2c01359. Epub 2022 Jun 27.
Pt-alloy (Pt-M) nanoparticles (NPs) with less-expensive 3d transition metals (M = Ni, Cu, Co) supported on high-surface-area carbon supports are currently the state-of-the-art (SoA) solution to reach the production phase in proton exchange membrane fuel cells (PEMFCs). However, while Pt-M electrocatalysts show promise in terms of increased activity for oxygen reduction reaction (ORR) and, thus, cost reductions from the significantly lower use of expensive and rare Pt, key challenges in terms of synthesis, activation, and stability remain to unlock their true potential. This work systematically tackles them with a combination of electrocatalyst synthesis and characterization methodologies including thin-film rotating disc electrodes (TF-RDEs), an electrochemical flow cell linked to an inductively coupled plasma mass spectrometer (EFC-ICP-MS), and testing in 50 cm membrane electrode assemblies (MEAs). In the first part of the present work, we highlight the crucial importance of the chemical activation (dealloying) step on the performance of Pt-M electrocatalysts in the MEA at high current densities (HCDs). In addition, we provide the scientific community with a preliminary and facile method of distinguishing between a "poorly" and "adequately" dealloyed (activated) Pt-alloy electrocatalyst using a much simpler and affordable TF-RDE methodology using the well-known CO-stripping process. Since the transition-metal cations can also be introduced in a PEMFC due to the degradation of the Pt-M NPs, the second part of the work focuses on presenting clear evidence on the direct impact of the lower voltage limit (LVL) on the stability of Pt-M electrocatalysts. The data suggests that in addition to intrinsic improvements in stability, significant improvements in the PEMFC lifetime can also be obtained the correct MEA design and applied limits of operation, namely, restricting not just the upper but equally important also the lower operation voltage.
负载在高比表面积碳载体上的、含有价格较为低廉的3d过渡金属（M = Ni、Cu、Co）的铂合金（Pt-M）纳米颗粒（NPs），是目前质子交换膜燃料电池（PEMFCs）进入生产阶段的最先进（SoA）解决方案。然而，尽管Pt-M电催化剂在提高氧还原反应（ORR）活性方面展现出前景，从而因大幅减少昂贵且稀有的铂的用量而降低成本，但在合成、活化和稳定性方面的关键挑战依然存在，有待挖掘其真正潜力。本工作通过结合电催化剂合成与表征方法系统地解决这些问题，这些方法包括薄膜旋转圆盘电极（TF-RDEs）、与电感耦合等离子体质谱仪相连的电化学流动池（EFC-ICP-MS）以及在50平方厘米膜电极组件（MEAs）中进行测试。在本工作的第一部分，我们强调了化学活化（脱合金化）步骤对Pt-M电催化剂在高电流密度（HCDs）下MEA性能的至关重要性。此外，我们为科学界提供了一种初步且简便的方法，即使用广为人知的CO溶出过程，通过更简单且经济的TF-RDE方法来区分“脱合金化（活化）不佳”和“脱合金化（活化）充分”的Pt合金电催化剂。由于Pt-M NPs的降解，过渡金属阳离子也可能引入PEMFC中，因此工作的第二部分着重展示关于较低电压极限（LVL）对Pt-M电催化剂稳定性直接影响的明确证据。数据表明，除了稳定性的内在提升外，通过正确的MEA设计和应用操作极限，即不仅限制上限而且同样重要地限制下限工作电压，还能显著提高PEMFC的寿命。
