Pulse electrodeposition of CuSbS2 thin films: Role of Cu/Sb precursor ratio on the phase formation and its performance as photocathode for hydrogen evolution§.

In this paper, we outline the development of stoichiometric chalcostibite, CuSbS2 thin films, from a single bath by pulse electrodeposition for its application as a photocathode in photoelectrochemical cells (PEC). The Cu/Sb precursor molar ratio of the deposition bath was varied to obtain stoichiometric CuSbS2 thin films. The optimized deposition and dissolution potentials were -0.72 V and -0.1 V vs saturated calomel electrode, respectively. The formation of CuSbS2 was analyzed using different characterization tools. X-ray diffraction and Raman results showed the formation of the pure chalcostibite phase from a precursor bath with molar ratio Cu/Sb = 0.41. The heterostructure CuSbS2/CdS/Pt was tested as a photocathode in the PEC. The energy positions of the conduction and valence bands were estimated from the Mott Schottky plots. The conduction band and valence band offset of CuSbS2/CdS heterojunction were 0.1 eV and 1.04 eV, respectively. The electric field created in the junction reduced the recombination of the electron/hole pairs and improved charge transfer in the interface. The heterostructure CuSbS2/CdS/Pt demonstrated an improved photocurrent density of 3.4 mA cm-2 at 0 V vs reversible hydrogen electrode. The PEC efficiency obtained from the CuSbS2/CdS heterojunction was 0.56 %. Therefore, we demonstrated the feasibility of an inexpensive technique like electrodeposition for the development of an efficient earth-abundant photocathode.

"Click" Methodology for the Functionalization of Water Oxidation Catalyst Iridium Oxide Nanoparticles with Hydrophobic Dyes for Artificial Photosynthetic Constructs.

The unusually high tolerance toward chemical functional groups of the copper(I)-catalyzed Huisgen-Sharpless-Meldal 1,3-dipolar cycloaddition of azides and alkynes protocol (the CuAAC or "click" reaction) associated with its mild conditions and high yields has been explored in the present methodology to successfully prepare water oxidation catalyst iridium oxide nanoparticles decorated with organic dyes. The "click reaction" has proven to be an excellent synthetic tool to overcome the incompatible solubility of the hydrophilic iridium oxide nanoparticles and the hydrophobic dyes. A complex artificial photosynthetic model designed to mimic the photoinduced redox processes occurring in photosystem II is used as a hydrophobic dye to highlight the efficiency and selectiveness of the method.