Seminar Pascual Oña Burgos

Small molecule activation, such as H2O, H2, N2, O2 or CO2, constitutes a critical frontier of chemical science, potentially removing the hazardous global warming gases and providing chemical precursors from Earth’s most abundant molecules. In this talk, we shall explore how homo and heterometallic complexed can be used as building blocks to achieve different solid materials, ranging from MOFs to supported metal nanoparticles, showing enhanced efficiency in these processes.
Specifically, Water splitting is one of the key processes for many energy storage and conversion applications, being water oxidation or oxygen evolution reaction (OER) still considered the most challenging step. In this regard, cobalt-based metal-organic frameworks (MOFs) have recently attracted great interest due to their notable electrocatalytic OER activity and the abundance of this metal on Earth.1,2 Based on that idea, we developed a new cobalt metal−organic framework (2D-Co-MOF) with well-defined layered double cores strongly connected by intermolecular bonds (Figure 1a). In situ electrochemically activated 2D-Co-MOF@Nafion exhibits an outstanding electrocatalytic performance for the OER at neutral pH and a high robustness. The particular coordination chemistry of the MOF consisting of a regular arrangement of multiple Co(II) redox metal sites connected by appropriate organic ligands explains the higher catalytic activity of this MOF.
Another challenge still to be met in water splitting is finding a multifunctional electrocatalyst. In that sense, the benchmark HER electrocatalysts are Pt-based materials. However, they are not suitable for OER. On the other hand, Ir and Ru oxides are state-of-art OER electrocatalysts. Unfortunately, they show insufficient activity toward HER.
On the lookout for these multifunctional systems, we reported a supported Fe-doped Pd-nanoparticles (NPs) prepared via soft transformation of a PdFe-MOF.3 The thus synthesized bimetallic PdFe NPs are supported on FeOx@C layers, essential for developing well-defined and distributed small NPs. The application of this material (PdFe@FeOx-C) as a multifunctional nanocatalyst for the electrocatalytic water splitting process has been investigated with promising results in terms of favourable intrinsic activity, wide pH window and high stability (Figure 2b).4 More recently, we developed a straightforward, efficient, and robust synthesis of mono- and bimetallic nanoparticles promoted through a commercially available metallic source, the Wilkinson complex, in order to prepare Rh2P nanoparticles, which have high crystallinity and are coated with graphitic carbon patches.5 The resulting materials have been tested in electrocatalytic HER and OER processes at acid, alkaline and neutral media, providing superb HER activity and competitive OER performance, particularly at neutral and alkaline media, compared to the benchmark HER and OER electrocatalysts Pt and RuOx/IrOx, respectively.6

References
[1] Gutiérrez Tarriño, S.; Olloqui-Sariego, J. L.; Calvente, J. J.; Palomino, M.; Minguez Espallargas, G.; Jorda, J. L.; Rey, F.; Oña-Burgos, P. ACS Appl. Mat. and Interfaces, 2019, 11, 46658-46665.
[2] Gutiérrez-Tarriño, Olloqui-Sariego, J. L.; Calvente, J. J.; Minguez Espallargas, G.; Rey, F.; Corma, A.; Oña-Burgos, P. J. Am. Chem. Soc. 2020, 142, 19198−19208.
[3] Martínez, J.; Mazarío, J.; Mínguez, G. E.; Oña-Burgos, P. Chem. A Eur. J. 2020, 26, 13659.
[4] Martínez, J.; Mazarío, J.; Olloqui-Sariego, J. L.; Oña-Burgos, P. Adv. Sustainable Syst. 2022, 6, 2200096.
[5] Galdeano-Ruano, C.; Corma, A.; Oña-Burgos, P. ACS Appl. Nano Mater. 2021, 4, 10743.
[6] Galdeano-Ruano, C.; Olloqui-Sariego, J. L.; Oña-Burgos, P. J. of Catalysis submitted.