Electrodeposition of Ni-doped MoS2 Thin Films

Ni-doped MoS2 thin films were fabricated by electrodeposition from electrolytes containing both MoS42− and varying concentrations of Ni2+, followed by annealing at 400 °C for 2 h in an Ar atmosphere. The film resistivity decreased from 32.8 -cm for un-doped MoS2 to 11.3 -cm for Ni-doped MoS2 containing 9 atom% Ni. For all Ni dopant levels studied, only the X-ray diffraction (XRD) pattern expected for MoS2 is observed, with the average grain size increasing with increasing Ni content. Ni-doped MoS2 thin films were tested for their activity towards the hydrogen evolution reaction (HER) in 0.5 M H2SO4. Tafel equation fits reveal that the catalytic activity for the HER, as measured by the exchange current density, increases up to 6 atom% Ni, and then decreases slightly for 9 atom% Ni. Ni-doped MoS2 thin films were also tested in 1.0 M Na2SO4 for use within electrochemical supercapacitors, and the capacitance per unit area increases by 2-3x for 9 atom% Ni-doped MoS2 relative to un-doped MoS2. The highest capacitance obtained for Ni-doped MoS2 during galvanostatic charge-discharge measurements is ∼300 F g−1.