Hierarchical Cu2−XSe nanotubes constructed by two-unit-cell-thick nanosheets: room-temperature synthesis and promoted electrocatalytic activity towards polysulfides

Hierarchical Cu2−XSe nanotubes, constructed by nanosheets with a thickness of two unit cells (1.2 nm), have been fabricated with Cu(OH)2 nanorod arrays as self-sacrificial templates at room temperature, with a high surface area of 72.3 m2 g−1. The unique structure of the Cu2−XSe nanotubes leads to high electrocatalytic activity towards the reduction of polysulfides, given their enlarged active surface area, rapid transportation of electrons and mass. As a result, quantum dot-sensitized solar cells (QDSSCs) with the obtained Cu2−XSe nanotubes as the counter electrode material exhibit long-term stability and a high power conversion efficiency of 5.14% (1 sun irradiation simulation), better than those of the commonly-used Cu2S/brass (3.38%) and reference Pt (1.78%) electrodes.