Electrodeposition of Cu-Doped MoS₂for Charge Storage in Electrochemical Supercapacitors

Cu-doped MoS 2 thin films were prepared by one-step electrodeposition from 10.0 mM (NH 4 ) 2 MoS 4 , 5.0 mM CuSO 4 , 0.10 M KCl and 0.50 M KSCN at pH 6.95, followed by annealing for three hr. at 500°C in Ar. Cyclic voltammetry in the presence of the SCN — complexing agent yields a cathodic deposition peak that is slightly anodically shifted (∼90 mV) relative to the cathodic deposition peaks observed for elecrolytes containing only Cu 2+ and only MoS 4 2− . This may provide evidence for the induced co-deposition mechanism, but it is unclear which specific compound is formed. According to RBS and EDX analysis, thin film deposits contain 1–4 atom% Cu and are sulfur-deficient relative to stoichiometric MoS 2 . Cu dopant incorporation reduces the film resistivity by ∼10x relative to undoped MoS 2 . The specific capacitaqnce of Cu-doped MoS 2 was also measured by both cyclic voltammetry (CV) and galvanostatic charge-dischrarge (GCD). For 500 nm thick annealed MoS 2 films, the specific capacitance of Cu-doped films ranges from 2.5–3.5x higher than that of undoped films during 1000 cycles of CV testing in 1.0 M Na 2 SO 4 . Capacitance testing also reveals better capacity retention and high scan rate performance for Cu-doped relative to undoped MoS 2 films.