Ambient Aqueous Growth of Cu₂Te Nanostructures with Excellent Electrocatalytic Activity toward Sulfide Redox Shuttles

A new aqueous and scalable strategy to synthesize surfactant-free Cu₂Te nanotubes and nanosheets at room temperature has been developed. In aqueous solution, Cu₂E (E = O, S, Se) nanoparticles can be easily transformed into Cu₂Te nanosheets and nanotubes via a simple anion exchange reaction under ambient conditions. The formation of Cu₂Te nanosheets is ascribed to a novel exchange-peeling growth mechanism instead of simple Kirkendall effect; and the resultant nanosheets can be further rolled into nanotubes with assistance of stirring. The morphologies of Cu₂Te nanosheets and nanotubes can be easily controlled by changing the synthesis parameters, such as the concentration of precursors, the size of nanoparticle precursor, and the amount of NaBH₄, as well as the stirring speed. Thus-formed Cu₂Te nanostructures exhibit excellent catalytic activity toward sulfide redox shuttles and are exploited as counter electrodes catalysts for quantum dot sensitized solar cells. The performance of Cu₂Te nanostructures strongly depends on their morphology, and the solar cells made with counter electrodes from Cu₂Te nanosheets show the maximum power conversion efficiency of 5.35%.