Synthesis of CeO_x‐Decorated Pd/C Catalysts by Controlled Surface Reactions for Hydrogen Oxidation in Anion Exchange Membrane Fuel Cells

Abstract

Due to the sluggish kinetics of the hydrogen oxidation reaction (HOR) in alkaline electrolytes, the development of more efficient HOR catalysts is essential for the next generation of anion‐exchange membrane fuel cells (AEMFCs). In this work, CeOx is selectively deposited onto carbon‐supported Pd nanoparticles by controlled surface reactions, aiming to enhance the homogenous distribution of CeOx and its preferential attachment to Pd nanoparticles, to achieve highly active CeOx‐Pd/C catalysts. The catalysts are characterized by inductively coupled plasma–atomic emission spectroscopy, X‐ray diffraction, high‐resolution transmission electron microscopy, scanning transmission electron microscopy (STEM), electron energy loss spectroscopy, and X‐ray photoelectron spectroscopy to confirm the bulk composition, phases present, morphology, elemental mapping, local oxidation, and surface chemical states, respectively. The intimate contact between Pd and CeOx is shown through high‐resolution STEM maps. The oxophilic nature of CeOx and its effect on Pd are probed by CO stripping. The interfacial contact area between CeOx and Pd nanoparticles is calculated for the first time and correlated to the electrochemical performance of the CeOx‐Pd/C catalysts. Highest recorded HOR specific exchange current (51.5 mA mg−1Pd) and H2–O2 AEMFC performance (peak power density of 1,169 mW cm−2 mgPd−1) are obtained with a CeOx‐Pd/C catalyst with Ce0.38/Pd bulk atomic ratio.

Effect of the Synthetic Method on the Properties of Ni-Based Hydrogen Oxidation Catalysts

“… 1 − 3 This progress is the result of the development of anion-exchange membranes (AEMs) with higher OH – ion conductivity and stability, 4 , 5 as well as the growth in the understanding of the AEMFC water management. 6 The progress is also significantly driven by the advancement in oxygen reduction 7 , 8 and hydrogen oxidation electrocatalysts 9 − 12 for alkaline media. Until now, mainly platinum group metals (PGMs), namely Pt, PtRu, and Pd-based 13 − 15 catalysts, are tested in fuel cells at relatively high loading levels, up to 0.6 mg cm –2 , on either or both electrodes of AEMFCs.…”

Porphyrin Aerogel Catalysts for Oxygen Reduction Reaction in Anion‐Exchange Membrane Fuel Cells

“…The HT800‐FeP aerogel, which exhibited the highest catalytic performance, was used to prepare an electrode via the gas diffusion electrode method reported elsewhere, [ 11,51–53 ] and tested in an AEMFC. The catalyst was first crushed and ground into a fine powder in a closed container.…”

Recent Insights on Catalyst Layers for Anion Exchange Membrane Fuel Cells

“…Furthermore, the atomic ratio of Pd/Ce bulk was adjusted [ 66 ] to optimize the interfacial contact area of Pd and CeO x by controlled surface reactions (CSRs). Figure a shows the transmission electron microscopy (TEM) and electrochemical analysis have a correlation related to the interfacial contact area of Pd–CeO x .…”

“…Reproduced with permission. [ 66 ] Copyright 2020, Wiley‐VCH. b) Schematic diagram of RSDT for the synthesis of Pd–CeO 2 /C catalysts.…”