Metal–support interaction between titanium oxynitride and Pt nanoparticles enables efficient low-Pt-loaded high-performance electrodes at relevant oxygen reduction reaction current densities

Hrnjić, Armin (author), Kamšek, Ana Rebeka (author), Bijelić, Lazar (author), Logar, Anja (author), Maselj, Nik (author), Smiljanić, Milutin (author), Trputec, Jan (author), Vovk, Natan (author), Pavko, Luka (author), Ruiz-Zepeda, Francisco (author), Bele, Marjan (author), Jovanovič, Primož (author), Hodnik, Nejc (author)

In the present work, we report on a synergistic relationship between platinum nanoparticles and a titanium oxynitride support (TiO$_x$N$_y$/C) in the context of oxygen reduction reaction (ORR) catalysis. As demonstrated herein, this composite configuration results in significantly improved electrocatalytic activity toward the ORR relative to platinum dispersed on carbon support (Pt/C) at high overpotentials. Specifically, the ORR performance was assessed under an elevated mass transport regime using the modified floating electrode configuration, which enabled us to pursue the reaction closer to PEMFC-relevant current densities. A comprehensive investigation attributes the ORR performance increase to a strong interaction between platinum and the TiO$_x$N$_y$/C support. In particular, according to the generated strain maps obtained via scanning transmission electron microscopy (STEM), the Pt-TiO$_x$N$_y$/C analogue exhibits a more localized strain in Pt nanoparticles in comparison to that in the Pt/C sample. The altered Pt structure could explain the measured ORR activity trend via the d-band theory, which lowers the platinum surface coverage with ORR intermediates. In terms of the Pt particle size effect, our observation presents an anomaly as the Pt-TiO$_x$N$_y$/C analogue, despite having almost two times smaller nanoparticles (2.9 nm) compared to the Pt/C benchmark (4.8 nm), manifests higher specific activity. This provides a promising strategy to further lower the Pt loading and increase the ECSA without sacrificing the catalytic activity under fuel cell-relevant potentials. Apart from the ORR, the platinum-TiO$_x$N$_y$/C interaction is of a sufficient magnitude not to follow the typical particle size effect also in the context of other reactions such as CO stripping, hydrogen oxidation reaction, and water discharge. The trend for the latter is ascribed to the lower oxophilicity of Pt-based on electrochemical surface coverage analysis. Namely, a lower surface coverage with oxygenated species is found for the Pt-TiO$_x$N$_y$/C analogue. Further insights were provided by performing a detailed STEM characterization via the identical location mode (IL-STEM) in particular, via 4DSTEM acquisition. This disclosed that Pt particles are partially encapsulated within a thin layer of TiO$_x$N$_y$ origin.

• Language: English
• Keywords: oxygen reduction reaction, titanium oxynitride support, metal−support interaction, floating electrode, 4DSTEM, electrodes, metal nanoparticles, oxides, platinum, redox reactions
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: Str. 2473–2486
• Numbering: Vol. 14, iss. 4
• PID: 20.500.12556/RUL-156060
• UDC: 620.1/.2
• ISSN on article: 2155-5435
• DOI: 10.1021/acscatal.3c03883
• COBISS.SI-ID: 187187459
• Publication date in RUL: 06.05.2024

Record is a part of a journal

• Title: ACS catalysis
• Shortened title: ACS catal.
• Publisher: American Chemical Society
• ISSN: 2155-5435
• COBISS.SI-ID: 518529817

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: materiali, titan, reakcija redukcije kisika, ORR