Insight into the Modification of the Low-Pt Electrocatalysts By the Defective Metal Oxide Additives: The Effect on the Oxygen Reduction Reaction in Acid Media
Authors: Kostuch Aldona , Negro Enrico , Di Noto Vito , Zoladek Sylwia , Rutkowska Iwona A. , Kulesza Pawel 
Published: December 2024

The global rise in energy consumption combined with severe environmental issues and climate change has promoted the development of green alternative technologies such as low-temperature proton exchange membrane fuel cells (PEMFCs). However, the performance and operational cost of PEMFC largely depend on the application of highly expensive state-of-the-art Pt-based systems, which are so far the most effective catalysts for the oxygen reduction reaction (ORR) at the fuel cell’s cathode. The widespread commercialization of the PEMFC technology has also been complicated by the limited lifetime of catalytic systems due to the instability of carbon supports as well as Pt catalytic centers. Due to these facts, it is of great significance to gain an in-depth insight into the ORR mechanism to optimize the activity of the ORR catalytic centers and their more efficient utilization while minimizing the Pt content without loss of performance and durability, which are essential features to ensure wider use of the low-temperature hydrogen-oxygen fuel cell systems. One of the reasonable strategies for ameliorating stability, and selectivity of carbon-supported low Pt content electrocatalysts for the ORR in acid media is their functionalization by selected nanostructured non-noble metal oxides (MOx)1. The strong mutual interactions between all components in such hybrid material (Pt, C, MOx) are capable of tuning the Pt electronic structure at the electrocatalytic interface, thus promoting centers for the adsorption of oxygen and the cleavage of O=O bonds as well as the durability of the carbon carriers can be improved under highly aggressive acidic conditions. Additionally, the application of metal oxide co-catalysts which are capable of inducing the decomposition of hydrogen peroxide and/or scavenging of free radicals can make a significant contribution to improving the durability and overall efficiency of fuel cells.

Due to the unique structure, redox ability, oxygen vacancies, and other features resulting from the 4f electronic configuration of cerium, in the present studies, we synthesis the reduced CeOx nanostructured and investigate the influence of such additive on the stability and selectivity of low-Pt content electrocatalysts in the oxygen reduction reaction (ORR) in acidic media. The stable oxide phases with the tailored redox properties and the presence of oxygen vacancies were obtained by controlling their morphology and composition. Preparation of small ceria nanoparticles by microwave-assisted hydrothermal method and introduction of various dopants (e.g. Pr, Nb, Cu) into these oxide structures improve its reducibility and non-stoichiometry phase content, optimizing important parameters for catalytic activity. The received results revealed that the CeOx/M-CeOx additive is allowed to obtain a lower amount of undesirable H2O2 produced during the ORR and improve the Pt/C stability. It is assumed that the improved durability and the better selectivity towards 4e– reduction of oxygen of the modified catalyst result from the defective cerium oxide properties and strong interactions between all components.

Acknowledgments: This research was funded by the National Science Center (Poland) under Sonatina Project (2022/44/C/ST5/00077) and under the auspices of the European Union EIT Raw Materials ALPE 19247 Project (Specific Grant Agreement No. EIT/RAW MATERIALS/SGA2020/1).

References:

[1] Kostuch, A.; Rutkowska, I. A.; Dembinska, B.; Wadas, A.; Negro, E.; Vezzu, K.; Di Noto, V.; Kulesza, P. J. Enhancement of Activity and Development of Low Pt Content Electrocatalysts for Oxygen Reduction Reaction in Acid Media. Molecules
2021, 26, 5147.