Facile multilayer assemble of a mixed-valence Mn4-containing silicotungstate and its electrochemical study with Co3O4 as co-catalyst for photoelectrocatalytic water oxidation

In this work, three Mn-containing silicotungstates were prepared according to the published procedures, Na2.5K4.5[Mn-3(II)(OH)(3)(H2O)(3)(A-alpha-SiW9O34)]center dot 15H(2)O (NaK-Mn3), K4[MnIII3 (OH)3(H2O)3 (A-alpha-SiW9O34)]center dot 10H(2)O (KMn3) and Na3.5K2.5[Mn-3(III) MnIVO3(CH3COO)3 (A-alpha-SiW9O34)]center dot 20H(2)O center dot NaCH3COO center dot 0.5KCH(3)COO (NaK-Mn4), and then their electrochemical behaviors were studied at pH 5 and electrocatalytic activities for water oxidation were compared at pH 7. Furthermore, the compound NaK-Mn4, which displayed the best catalytic activity for the water oxidation among three silicotungstates, is chosen to construct the composite films using PDDA (PDDA: poly(diallyldimethylammonium chloride)) or Co3O4 components through layer-by-layer (LbL) method and the fabricated composite films were proved by measuring cyclic voltammogram (CV) curves and UV-visible spectra. Additionally, taking the advantage of Co3O4 as a photocatalyst, the photoelectrocatalytic performance of the composite film [Mn-4/Co3O4] towards the water oxidation was investigated. The results indicate that the designed composite film shows enhanced catalytic activity for the water oxidation.

Automated summary

In this study, three Mn-containing silicotungstates were synthesized and their electrochemical behaviors for water oxidation were investigated. Among them, NaK-Mn4 displayed the best catalytic activity and was chosen to construct composite films, which showed enhanced catalytic activity for water oxidation. The photoelectrocatalytic performance of the composite film [Mn-4/Co3O4] was further studied and demonstrated improved catalytic activity for water oxidation.