(Invited) Redox Chemistries for Vacancy Modulation in Copper Phosphide Nanocrystals

Copper phosphide has been proposed as an anode material for lithium-ion batteries due to the ability to accommodate the electrochemical insertion of Li ions without substantial reorganization of the P-sublattice. We present three copper-coupled redox chemistries that allow post-synthetic modulation of the delocalized hole concentrations in colloidal copper phosphide nanocrystals. Changes in the structural, optical, and compositional properties are evaluated by powder X-ray diffraction, electronic absorption spectroscopy, solid-state nuclear magnetic resonance spectroscopy and elemental analysis. The redox chemistries presented herein can be used to obtain nanocrystals with Cu/P ratios of ~2.66–2.93, a larger range than has been possible through purely synthetic tuning. Importantly, oxidation with a divalent metal halide and trioctylphosphine allows access to a uniquely Cu-deficient composition. Copper phosphide nanocrystal thin-films oxidized in this way would be ideal candidates for fundamental electrochemical lithiation studies.