Design Rules for Mixed Rutile PGM Oxides
4 affiliations
- 1Department of Chemistry, University College London, 20 Gordon Street, London, United Kingdom, WC1H 0AJ
- 2Johnson Matthey Technology Centre, Blounts Court Road, Sonning Common, Reading, United Kingdom, RG4 9NH
- 3School of Chemistry
- 4University of Birmingham
Abstract
Oxide solid solutions have important industrial applications including catal-ysis that require high stability under operating conditions. The stability of solid solutions is usually predicted using structural similarity, with low lattice mismatch resulting in stable solid solutions and high lattice mismatch resulting in unstable solid solutions. While this works for most solid solutions, some such as yttria-stabilised zirconia break the rules and remain stable due to other factors. Here we use density functional theory to study the substitutional solid solutions of the rutile platinum group metal (PGM) oxides IrO 2 and RuO 2 . These PGM oxides are commonly used as oxygen evolution reaction (OER) catalysts in proton exchange membrane (PEM) water electrolysers and both suffer from degradation in the harsh acidic conditions. In an effort to stabilise the PGM oxides and determine what factors affect the mixing thermodynamics, we mix the PGM oxides with each other and four other rutile oxides with different properties. Our results for the nine unique systems, including both PGM-only and PGM/non-PGM solid solutions, show that the mixing thermodynamics can be predicted using two new mixing rules. Firstly, rutile oxide solid solutions have negative mixing enthalpies when both solutes are metallic and positive mixing enthalpies otherwise. This is independent of all other factors. Secondly, increasing the electronegativity difference between solute metals decreases the mixing enthalpies as long as the first rule remains unbroken. This was shown by NbO 2 having the most favourable mixing with the PGM oxides despite its larger lattice. We hope these new mixing rules can be used to design new stable solid solutions of rutile oxides such as IrO 2 and RuO 2 .
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BibTeX
@misc{samli2026design,
title = {{Design Rules for Mixed Rutile PGM Oxides}},
author = {Alp Eren Samli and Rachel Nathaniel Kerber and Laure Briquet and Misbah Sarwar and David O. Scanlon},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15009724/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009724/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Design Rules for Mixed Rutile PGM Oxides
AU - Alp Eren Samli
AU - Rachel Nathaniel Kerber
AU - Laure Briquet
AU - Misbah Sarwar
AU - David O. Scanlon
PY - 2026
DA - 2026/10/01
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009724/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009724/v1
AB - Oxide solid solutions have important industrial applications including catal-ysis that require high stability under operating conditions. The stability of solid solutions is usually predicted using structural similarity, with low lattice mismatch resulting in stable solid solutions and high lattice mismatch resulting in unstable solid solutions. While this works for most solid solutions, some such as yttria-stabilised zirconia break the rules and remain stable due to other factors. Here we use density functional theory to study the substitutional solid solutions of the rutile platinum group metal (PGM) oxides IrO 2 and RuO 2 . These PGM oxides are commonly used as oxygen evolution reaction (OER) catalysts in proton exchange membrane (PEM) water electrolysers and both suffer from degradation in the harsh acidic conditions. In an effort to stabilise the PGM oxides and determine what factors affect the mixing thermodynamics, we mix the PGM oxides with each other and four other rutile oxides with different properties. Our results for the nine unique systems, including both PGM-only and PGM/non-PGM solid solutions, show that the mixing thermodynamics can be predicted using two new mixing rules. Firstly, rutile oxide solid solutions have negative mixing enthalpies when both solutes are metallic and positive mixing enthalpies otherwise. This is independent of all other factors. Secondly, increasing the electronegativity difference between solute metals decreases the mixing enthalpies as long as the first rule remains unbroken. This was shown by NbO 2 having the most favourable mixing with the PGM oxides despite its larger lattice. We hope these new mixing rules can be used to design new stable solid solutions of rutile oxides such as IrO 2 and RuO 2 .
ER -