Keggin-type polyoxometalate/thiospinel octahedron heterostructures for photoelectronic devices
All-inorganic heterostructures has attracted intense interest in the fields of new energy and environmental applications recently, especially in photoelectronic devices. Herein, we firstly obtain a novel CoIn2S4 thiospinel octahedron through a simple one-step hydrothermal synthesis method. On this basis we further propose a strategy to prepare the all-inorganic heterostructures (NH4)4CoⅡ[CoⅡW12O40]·20H2O/CoIn2S4 (CoW12-n/CoIn2S4, n represents mole number of CoW12) through doping Keggin-type polyoxometalate (POM). The addition of POM can alleviate the cross-growth of CoIn2S4 octahedron, increase the specific surface area and the amount of exposed active site of the heterostructures. What's more, we investigate the electrocatalytic triiodide reduction properties of the heterostructures. Electrochemical measurments exhibits that POM contents has an obviosuly influence on the catatytic activity of this heterostructure catalyst. The CoW12-0.3/CoIn2S4 heterostructures present the best catalytic performance and the lowest charge transfer resistance. Consequently, the dye-sensitized solar cells (DSSC) with CoW12-0.3/CoIn2S4 heterostructures as a counter electrode (CE) shows highest photovoltaic conversion efficiency (PCE) up to 6.79%, superior to that of the Pt CE (5.83%). This work not only provides an approach for designing composites for efficient electrocatalytic triiodide reduction, but also represents a further step towards the application of all-inorganic heterostructures in photoelectronic devices.