Understanding polyoxometalates as water oxidation catalysts through iron vs. cobalt reactivity

Autor segons l'article: Azmani K; Besora M; Soriano-López J; Landolsi M; Teillout AL; de Oliveira P; Mbomekallé IM; Poblet JM; Galán-Mascarós JR

Departament: Química Física i Inorgànica

Autor/s de la URV: Azmani, Khalid / Besora Bonet, Maria / Poblet Rius, Josep Maria

Paraules clau: Water oxidation catalysts; Structure-reactivity relationships; Solid-state electrodes; Proton coupled electron transfers; Polyoxometalates; Phosphate; Oxygen-evolution; Oxygen evolution reaction (oer); Oxidation; Molecular-orbital methods; Iron compounds; Hydrogen; Homogeneous catalyst; Exchange; Energy; Electronic differences; Electron transport properties; Electrocatalysts; Computational calculations; Computational analysis; Cobalt; Catalysts; Activation energy; Abundant transition-metal; Ab-initio

Resum: Cobalt polyoxometalates (Co-POMs) have emerged as promising water oxidation catalysts (WOCs), with the added advantage of their molecular nature despite being metal oxide fragments. In comparison with metal oxides, that do not offer well-defined active surfaces, POMs have a controlled, discrete structure that allows for precise correlations between experiment and computational analyses. Thus, beyond highly active WOCs, POMs are also model systems to gain deeper mechanistic understanding on the oxygen evolution reaction (OER). The tetracobalt Weakley sandwich [Co-4(II)(H2O)(2)(B-alpha-PW9O34)(2)](10-) (Co-4-WS) has been one of the most extensively studied. We have compared its activity with that of the iron analog [Fe-4(III)(H2O)(2)(B-alpha-PW9O34)(2)](6-) (Fe-4-WS) looking for the electronic effects determining their activity. Furthermore, the effect of POM nuclearity was also investigated by comparison with the iron- and cobalt-monosubstituted Keggin clusters. Electrocatalytic experiments employing solid state electrodes containing the POMs and the corresponding computational calculations demonstrate that Co-II-POMs display better WOC activity than the Fe-III derivatives. Moreover, the activity of POMs is less influenced by their nuclearity, thus Weakley sandwich moieties show slightly improved WOC characteristics than Keggin clusters. In good agreement with the experimental data, computational methods, including pK(a) values, confirm that the resting state for Fe-POMs in neutral media corresponds to the S-1 (Fe-III-OH) species. Overall, the proposed reaction mechanism for Fe-4-WS is analogous to that found for Co-4-WS, despite their electronic differences. The potential limiting step is a proton-coupled electron transfer event yielding the active S-2 (Fe-IV=O) species, which receives a water nucleophilic attack to form the O-O bond. The latter has activation energies slightly higher than those computed for the Co-POMs, in good agreement with experimental observations. These results provide new insights for the accurate understanding of the structure-reactivity relationships of polyoxometalates in particular, and or metal oxides in general, which are of utmost importance for the development of new bottom-up synthetic approaches to design efficient, robust and non-expensive earth-abundant water oxidation catalysts.

Àrees temàtiques: Química; Materiais; Interdisciplinar; General chemistry; Farmacia; Ciências biológicas iii; Ciências biológicas i; Chemistry, multidisciplinary; Chemistry (miscellaneous); Chemistry (all); Astronomia / física

Accès a la llicència d'ús: https://creativecommons.org/licenses/by/3.0/es/

Adreça de correu electrònic de l'autor: maria.besora@urv.cat; josepmaria.poblet@urv.cat

Data d'alta del registre: 2025-01-28

Volum de revista: 12

Versió de l'article dipositat: info:eu-repo/semantics/publishedVersion

Enllaç font original: https://pubs.rsc.org/en/content/articlelanding/2021/SC/D1SC01016F#!divAbstract

URL Document de llicència: https://repositori.urv.cat/ca/proteccio-de-dades/

Referència a l'article segons font original: Chemical Science. 12 (25): 8755-8766

Referència de l'ítem segons les normes APA: Azmani K; Besora M; Soriano-López J; Landolsi M; Teillout AL; de Oliveira P; Mbomekallé IM; Poblet JM; Galán-Mascarós JR (2021). Understanding polyoxometalates as water oxidation catalysts through iron vs. cobalt reactivity. Chemical Science, 12(25), 8755-8766. DOI: 10.1039/d1sc01016f

DOI de l'article: 10.1039/d1sc01016f

Entitat: Universitat Rovira i Virgili

Any de publicació de la revista: 2021

Tipus de publicació: Journal Publications