Pulse electrodeposition of CuSbS 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, CuSbS 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 CuSbS thin films. The optimized deposition and dissolution potentials were -0.72 V and -0.1 V vs saturated calomel electrode, respectively. The formation of CuSbS 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 CuSbS/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 CuSbS/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 CuSbS/CdS/Pt demonstrated an improved photocurrent density of 3.4 mA cm at 0 V vs reversible hydrogen electrode. The PEC efficiency obtained from the CuSbS/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.