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

Abstract

Cobalt polyoxometalates (Co-POMs) have emerged as promising water oxidation catalysts (WOCs), with the added advantage on their molecular nature despite being metal oxides fragments. In comparison with metal oxides, that...

Tuning the Catalytic Water Oxidation Activity through Structural Modifications of High-Nuclearity Mn-oxo Clusters [Mn18M] (M = Sr2+, Mn2+)

“…Uniform single-crystals of Mn 19 formed within a few days. The title compound was characterized by FT-IR (Figure S1b), which matched that of the previously reported Mn 19 , and by Raman spectroscopy (Figure S2c).…”

“…In comparison with the catalytic activity previously reported by the Mn 19 cluster, Mn 18 Sr shows a reduction of ca. 60 mV in the onset overpotential.…”

“…Two 0.1 mg/mL catalysts stock solution were prepared by dispersing either Mn 18 Sr or Mn 19 in a 10 mM NaP i buffer aqueous solution at pH 7.0. For comparison of the water oxidation catalytic activity of these two catalysts, we employed 5 nmol of either Mn 18 Sr or Mn 19 in the experiments by injecting the corresponding volume of the stock solution into the vial. The final volume of the mixture was adjusted to 5 mL by the addition of NaP i buffer solution.…”

“…Therefore, earth-abundant-based materials with water oxidation catalytic capabilities have been explored in recent years [12,13]. A myriad of systems have been reported displaying diverse water oxidation activities, which comprise mono-or multinuclear organometallic molecular species [14,15], polyoxometalates [16][17][18][19], colloidal particles [20,21], homo-and heterometallic oxides [22][23][24], metal-organic frameworks [25,26] and even metal-free catalysts [27,28]. Moreover, heterogenization of molecular WOCs through their immobilization into solid supports enables the fabrication of hybrid systems that combine the high catalytic activity of molecular catalysts with the stability and recyclability of heterogeneous materials [29,30].…”

“…Our group recently reported the activity of a bioinspired, high-nuclearity Mn- (Mn 19 ), which contains 2,6-bis(hydroxymethyl)-p-cresol, a non-innocent, redox-active ligand that resembles the tyrosine residue Y161 in PS II [47]. Importantly, Mn 19 -modified carbon paste electrodes delivered high catalytic activity in neutral media, displaying 10 mA cm −2 and even 100 mA cm −2 at applied overpotentials of 482 and 654 mV, respectively. Despite the high activity shown by this cluster, we identified oxidation of the primary alcohols of the organic ligand as the main deactivation pathway leading to catalyst deactivation.…”