Towards Lead-Doped ZnS Nanocrystals for Solar Hydrogen Generation

Efficient and affordable energy conversion and energy storage technologies are required to meet society’s increasing demands. Semiconductor nanocrystals are particularly attractive materials for solar energy conversion applications, as their tunable optoelectronic properties can be manipulated to both optimize the absorbance of solar photons and to afford desirable electronic properties. Further tunability of binary systems can be realized through substitutional doping. However, doping can be difficult, as the dopants can cause significant lattice strain in the host crystals. Lead-doped ZnS nanocrystals are one promising material for the conversion of solar photons into storable fuels such as hydrogen gas. The ZnS conduction band is sufficiently high in energy to reduce protons, and the lead dopants are hypothesized to add filled states in the ZnS band gap, thereby extending the absorbance of the crystals into the visible region. This work details progress towards controllable doping of ZnS nanocrystals with lead cations using modified hot injection procedures. Preliminary results suggest that the temperature of the ZnS reaction matrix, the temperature of the Pb reaction flask, and the mole ratio between Pb and Zn can be used to afford various doped or non-doped products. Spectroscopic data will be shown to demonstrate doping-dependent optical and electronic properties in combination with high resolution transmission electron micrographs for structural information. The early results of this work suggest that functional materials for hydrogen gas generation may be readily synthesized from earth-abundant precursors, representing a viable option for future solar energy conversion platforms