A [Co19(OH)12]26+-Incorporating Polyoxotungstate for Electrocatalytic Oxygen Evolution

Considerable efforts have been devoted to the research of transition-metal oxides for oxygen evolution reaction (OER) catalysts. Polyoxometalates (POMs) are one of the typical compounds of transition-metal oxides. In particular, cobalt-containing POMs have attracted much attention as potential catalysts for the OER. In this work, a new [Co19(OH)12]26+ unit-incorporating polyoxotungstate, Na34[Co19(OH)12(α-SiW10O37)6]·46H2O (referred to as Co19Si6W60), has been successfully prepared and explored for highly efficient OER. The most obvious feature is that the giant [Co19(OH)12(α-SiW10O37)6]34- subunit in Co19Si6W60 consists of six dilacunary Keggin-type [α-SiW10O37]10- groups interlaced and wrapped around a hexagonal-like [Co19(OH)12]26+ nanosheet, forming a sandwich-type structure. Furthermore, in comparison with other well-known Co-containing Keggin-type POMs of [Co4(H2O)2(α-PW9O34)2]10- (denoted as Co4(PW9)2) and [α-CoW12O40]6- (denoted as CoW12) as well as cobalt oxide (CoO), the Co19Si6W60 electrocatalyst exhibits an overpotential of 329.4 mV at 10 mA·cm-2, a low Tafel slope of 80.8 mV·dec-1, and a high stability in 0.1 M KOH electrolyte for over 40 h at 60.0 mA·cm-2. The hydroxyl bridges in Co19Si6W60 characterized by cooperative Co-O-Co interactions and multiple catalytic active sites act as a key factor in improving the electrocatalytic performance of POMs, thereby offering a cost-effective electrocatalyst with potential applications in renewable energy.