Issue 19, 2024

S-doped TiN supported N, P, S-tridoped TiO2 with hetero-phase junctions for fuel cell startup/shutdown durability

Abstract

TiO2 layers codoped with N and P formed on S-doped TiN are recently developed platinum-group metal (PGM)-free catalysts (N, P-TiO2/S-TiN) for the oxygen reduction reaction (ORR) in acidic media. Conventional Pt-based catalysts lack durability as the necessary carbon supports are oxidized at high potentials (>1.0 V) during startup and shutdown. N, P-TiO2/S-TiN catalysts do not require carbon supports and are expected to tolerate oxidation at high potentials. However, N, P-TiO2/S-TiN loses ORR activity during startup or shutdown at potentials >1.0 V due to removal of N- and P-atoms. We therefore report a new pathway to enhance durability and ORR activity of N, P-TiO2/S-TiN. By annealing N, P-TiO2/S-TiN with NH4F under N2, ORR active anatase/rutile TiO2 hetero-phase junctions are produced in bulk with remaining TiN supports, and the surface O-atoms in the TiO2 lattice are substituted by S2−. S-doped TiN-supported N, P, S-tridoped TiO2 exhibits the highest ORR activity among reported oxide/oxynitride catalysts, although the ORR activity of the N, P, S-TiO2/S-TiN catalyst remains lower than that of state-of-the-art carbon-based catalysts. The N, P, S-TiO2/S-TiN catalyst exhibits superior durability among PGM-free catalysts as the anionic dopants are not removed after 5000 potential cycles (1.0–1.5 V), leading to a 0.02 V reduction in half-wave potential.

Graphical abstract: S-doped TiN supported N, P, S-tridoped TiO2 with hetero-phase junctions for fuel cell startup/shutdown durability

Supplementary files

Article information

Article type
Paper
Submitted
03 3 2024
Accepted
17 4 2024
First published
17 4 2024

J. Mater. Chem. A, 2024,12, 11277-11285

S-doped TiN supported N, P, S-tridoped TiO2 with hetero-phase junctions for fuel cell startup/shutdown durability

M. Chisaka, J. A. Shamim, W. Hsu and H. Daiguji, J. Mater. Chem. A, 2024, 12, 11277 DOI: 10.1039/D4TA01475H

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