Increasing durability of Pt-surface-enriched nanosize structure catalysts by multi-step platinum deposition
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ORIGINAL PAPER
Increasing durability of Pt-surface-enriched nanosize structure catalysts by multi-step platinum deposition Dmitri Kaplan 1 & Meital Goor 1 & Larisa Burstein 2 & Inna Popov 3 & Meital Shviro 4 & Emanuel Peled 1 Received: 17 May 2020 / Revised: 24 June 2020 / Accepted: 5 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The sluggish reaction of oxygen reduction in proton-exchange membrane fuel cells (PEMFCs) and the durability of platinumbased catalysts have been major economical and technological barriers to the widespread application of PEMFCs. We report here on two Pt-surface-enriched nanosize structure (Pt-SENS) catalysts with iridium core, synthesized with the use of single-step and successive step-by-step electroless deposition of platinum. The synthesized catalysts were studied by energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and transmission scanning electron microscopy (STEM). Electrochemical analysis demonstrated improved oxygen reduction reaction (ORR) mass activity of the homemade catalysts by 25–30% compared with commercial 50%Pt/C catalyst and improved durability, by a factor of ~ 3, of the catalyst synthesized by successive step-by-step deposition following accelerated stress test (AST). Higher mass activities are attributed to better platinum utilization as a result of a Pt-surface-enriched structure, while greater durability is attributed to the stabilization of surface platinum by stronger Pt–Ir bonds induced by iridium atoms in the core. Keywords Platinum . Iridium . Durability . Catalyst . Synthesis . Oxygen . Reduction
Introduction Proton-exchange membrane fuel cells (PEMFCs) are seen as a highly efficient and clean potential power source for automotive, portable, and stationary applications [1, 2]. Although intensive PEMFC-related research and development have been performed in academic and industrial research facilities, there are two major remaining challenges hampering widespread fuel cell use: cost and durability [2, 3]. As a result of high platinum loadings, the cost of platinum is the highest factor in the total cost of a massproduced PEMFC stack [4], and the degradation of
platinum nanoparticles is a major contributor to the degradation of PEMFC performance. The target of the US Department of Energy (DOE) of 0.125 mgPGM cm−2 with a durability of 10% voltage degradation after 5000 h in automotive PEMFC by 2020 [5] is designed to mitigate cost and durability challenges. However, the current loadings are ~ 0.4 mg Pt cm −2 [6] (cathode only), and the achieved durability is ~ 4000 h [7]. To reduce platinum loading, Pt-alloy [8], de-alloyed [9], Pt-on-metal nanowire [10], and core-shell [11, 12] structures have been explored that use a less expensive core containing little or no platinum, while the shell is
* Emanuel Peled [email protected] Dmitri Kaplan [email protected]
Meital Shviro [email protected] 1
School of Chemistry, Tel Aviv University, 69978 Tel Aviv, Israel
2
Wolfson Applied Mat
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