Electrochemical nucleation and growth model of MoS2 for hydrogen evolution reaction

The electrochemical nucleation of MoS2 from a mixture of sodium molybdate dihydrate (Na2MoO4<middle dot>2H2O) and sodium sulphide (Na2S<middle dot>xH2O) aqueous solution on Cu substrate has been investigated. The nucleation and formation of molybdenum sulphide were investigated employing cyclic voltammetry and chronoamperometry studies. The experimental i-t curves observed at various overpotentials were compared to theoretical curves derived for the two limiting situations of the 3D instantaneous/progressive nucleation and growth model, as reported by Scharifker and Hills. The outcome of electrodeposition potential on nucleation rate (A) and nucleation density (N) was calculated from the current-time transients and SEM morphology obtained at - 1.1 V (5.75 x 1014 and 1.86 x 1015) was compared with - 0.9 V, - 1.0 V, and - 1.2 V, respectively. The investigation of the initial stages of the transient current-time relationships developed for MoS2 electrodeposition specified that film formation occurred progressively initially and instantaneous nucleation during the course of time. A HPMoS2 with an average size of 5-65 nm was obtained at -1.1 V and exhibited superior performance towards the hydrogen evolution reaction compared to samples obtained at - 0.9 V, - 1.0 V, and - 1.2 V.