Highly active nano-sized iridium catalysts: synthesis and operando spectroscopy in a proton exchange membrane electrolyzer

Chemical Science
Philipp LettenmeierK Andreas Friedrich

Abstract

A stable and cost effective oxygen evolution reaction (OER) catalyst is crucial for the large-scale market penetration of proton exchange membrane (PEM) water electrolyzers. We show that the synthesis of iridium nanoparticles in either low purity ethanol or water, or in the absence of a surfactant, is detrimental to the electrocatalytic properties of the materials. Adding NaBH4 in excess improves the purity of the catalyst enhancing the OER activity up to 100 A gIr-1 at 1.51 V vs. RHE, the highest value reported so far for high purity Ir nanoparticles. The measured OER activity correlates with the capacitive current rather than with the charge corresponding to the IrIII/IrIV oxidation peak. Operando near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) on membrane electrode assemblies (MEAs) with the synthesized catalysts reveals a metallic core surrounded by a thin layer of IrIII/IV oxides/hydroxides. Oxidation of IrIII leaves behind a porous ultrathin layer of IrIV oxides/hydroxides, which dominate the surface during the OER, while IrV was not detected.

References

Jun 4, 2014·Angewandte Chemie·Hernan G Sanchez CasalongueAnders Nilsson
Jul 15, 2015·Chemical Communications : Chem Comm·Viet-Ha TranSeiji Ogo
Jan 23, 2016·Physical Chemistry Chemical Physics : PCCP·Li WangK Andreas Friedrich
Aug 2, 2016·The Journal of Physical Chemistry Letters·Viktoriia A SavelevaElena R Savinova
May 17, 2017·Chemical Science·Verena PfeiferRobert Schlögl
Jan 1, 2015·Chemical Science·Elisa A PaoliIb Chorkendorff

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Citations

Jul 8, 2020·Advanced Materials·Taehyun KwonKwangyeol Lee
Jul 30, 2020·ACS Central Science·Dmitry LebedevChristophe Copéret
Mar 20, 2020·The Journal of Physical Chemistry Letters·Alexandra Zagalskaya, Vitaly Alexandrov
Jul 24, 2020·ACS Applied Materials & Interfaces·Eleonora CalìDavid J Payne

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Methods Mentioned

BETA
X-ray
transmission electron microscopy
electron diffraction

Software Mentioned

Digital Micrograph
QUASES
SESSA
- IMFP - TPP2M

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