Break-In Bad: On the Conditioning of Fuel Cell Nanoalloy Catalysts

Abstract

Preliminary testing of fuel cell catalysts in a model laboratory environment is an essential step in the technology readiness level progression of material candidates toward the commercial device. However, in the case of platinum alloy catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), there is no consensus on the protocol employed for catalyst conditioning (activation or break-in), leading to important discrepancies in the literature. Here, the effects of electrochemical conditioning on the PtNi nanocatalyst structure, chemical composition, and performance for the ORR are investigated using operando high-energy X-ray diffraction in both the liquid-electrolyte and solid-electrolyte X-ray transparent PEMFCs, online inductively coupled plasma mass spectrometry, and the rotating disk electrode (RDE) techniques, respectively. Our results show that for PtNi/C materials, the cost in ORR performance associated to complete surface stabilization at the potential of the ORR can be dramatic but can also be mitigated by adjusting the initial chemistry and structure of the catalyst. Overall, this study reveals how uncomplete catalyst conditioning in the RDE leads to highly erroneous conclusions regarding its performance and stability to be possibly found in a realistic PEMFC device and proposes simple strategies to close this gap.

Assessing Utilization Boundaries for Pt-Based Catalysts in an Operating Proton-Exchange Membrane Fuel Cell

“…16,17 It has been pointed out that the CCMmaking process, together with the activation potential cycling, can alter the catalyst morphology and composition to such an extent that the catalyst is no longer the same material as was synthesized, questioning the common approaches to catalyst activity testing using the RDE technique. 18 Our results provide further evidence that this is also the case for multimetallic oh-PtNiIr.…”

Origin of High Activity and Durability of Confined Ordered Intermetallic PtCo Catalysts for the Oxygen Reduction Reaction in Rotating Disk Electrode and Fuel Cell Operating Conditions

“…5−8 However, these advanced alloy catalysts encounter stability challenges, particularly due to the leaching of the nonprecious metals, which significantly impacts the catalyst activity and longevity. 2,9,10 To overcome these challenges, considerable efforts have been dedicated to enhancing the stability of Pt−M alloy catalysts through various strategies, such as developing core− shell structures, 11,12 applying dealloying treatment, 13,14 form-ing intermetallic phases, 8,15,16 and designing innovative catalyst architectures. 17,18 Among these methods, the atomic-ordered structure has been considered particularly effective in improving the stability of the catalysts by providing specific crystal and electronic structures.…”

“…Recently, proton-exchange membrane fuel cells (PEMFCs) have emerged as an important technology for applying hydrogen energy, aiming to reduce the dependence on fossil fuels. , However, the sluggish kinetics of the oxygen reduction reaction (ORR) in the PEMFC cathode necessitates the usage of the highly costed platinum, which hinderes the wide application of the PEMFCs. , Currently, alloying Pt with nonprecious metals (Pt–M, where M includes Zn, Cu, Ni, Co, Fe, etc.) has been demonstrated to be an effective approach to improve the intrinsic activity and diminish platinum usage. − However, these advanced alloy catalysts encounter stability challenges, particularly due to the leaching of the nonprecious metals, which significantly impacts the catalyst activity and longevity. ,, …”

Assessing Utilization Boundaries for Pt-based Catalysts in an Operating PEMFC

“…The top part of Figure 3 shows the evolution of scale factor (brown) for Pt(JM), while the bottom part shows the same for oh-PtNiIr. As the first CV cycle is clearly different from the subsequent ones due to impurity removal and reconstruction of the surface, only the second cycle is shown 33 . For more details about the measurement protocol, see the experimental section in supporting information.…”

“…Such a high loss of transition metal alloying element has been observed and discussed previously in the work of Gatalo and Dubau 31,32 . It has been pointed out that the CCM-making process, together with the activation potential cycling, can alter the catalyst morphology and composition to such an extent that the catalyst is no more the same material as synthesized, questioning the common approaches to catalyst activity testing using the RDE technique 33 . Our results provide further evidence that this is also the case for multimetallic oh-PtNiIr.…”