ABSTRACT
A unique reversible conversion-type mechanism is reported in the amorphous molybdenum polysulfide (a-MoS5.7) cathode material. The lithiation products of metallic Mo and Li2S2 rather than Mo and Li2S species have been detected. This process could yield a high discharge capacity of 746 mAh g-1. Characterizations of the recovered molybdenum polysulfide after the delithiaiton process manifests the high reversibility of the unique conversion reaction, in contrast with the general irreversibility of the conventional conversion-type mechanism. As a result, the a-MoS5.7 electrodes deliver high cycling stability with an energy-density retention of 1166 Wh kg-1 after 100 cycles. These results provide a novel model for the design of high-capacity and long-life electrode materials.
ABSTRACT
Molybdenum sulfides are considered to be one kind of the promising candidates as cheap and efficient electrocatalysts for hydrogen evolution reaction (HER). But this is still a gap on electrocatalytic performance toward Pt. To further enhance electrocatalytic activity of molybdenum sulfides, in this work, we prepared Mo3S13 films with high ratio of sulfur to molybdenum by electrodeposition. The Mo3S13 films exhibit highly efficient electrocatalytic activity for HER and achieve a current density of 10 mA/cm2 at an overpotential of 200 mV with an onset potential of 130 mV vs RHE and a Tafel slope of 37 mV/dec, which is superior to other reported MoS2 films. The highly electrocatalytic activity is attributed to high percentage of bridging S22- and apical S2- as well as good conductivity. This study provides an avenue for designing new molybdenum sulfides electrocatalysts.
