1 research outputs found
Low-temperature Synthesis of Heterostructures of Transition Metal Dichalcogenide Alloys (W<sub><i>x</i></sub>Mo<sub>1ā<i>x</i></sub>S<sub>2</sub>) and Graphene with Superior Catalytic Performance for Hydrogen Evolution
Large-area (ā¼cm<sup>2</sup>) films of vertical heterostructures
formed by alternating graphene and transition-metal dichalcogenide
(TMD) alloys are obtained by wet chemical routes followed by a thermal
treatment at low temperature. In particular, we synthesized stacked
graphene and W<sub><i>x</i></sub>Mo<sub>1ā<i>x</i></sub>S<sub>2</sub> alloy phases that were used as hydrogen
evolution catalysts. We observed a Tafel slope of 38.7 mV dec<sup>ā1</sup> and 96 mV onset potential (at current density of
10 mA cm<sup>ā2</sup>) when the heterostructure alloy was annealed
at 300 Ā°C. These results indicate that heterostructures formed
by graphene and W<sub>0.4</sub>Mo<sub>0.6</sub>S<sub>2</sub> alloys
are far more efficient than WS<sub>2</sub> and MoS<sub>2</sub> by
at least a factor of 2, and they are superior compared to other reported
TMD systems. This strategy offers a cheap and low temperature synthesis
alternative able to replace Pt in the hydrogen evolution reaction
(HER). Furthermore, the catalytic activity of the alloy is stable
over time, <i>i.e.</i>, the catalytic activity does not experience a significant
change even after 1000 cycles. Using density functional theory calculations,
we found that this enhanced hydrogen evolution in the W<sub><i>x</i></sub>Mo<sub>1ā<i>x</i></sub>S<sub>2</sub> alloys is mainly due to the lower energy barrier created by a favorable overlap of the d-orbitals from the transition metals and the s-orbitals of H<sub>2</sub>; with the lowest energy barrier occurring for the W<sub>0.4</sub>Mo<sub>0.6</sub>S<sub>2</sub> alloy. Thus, it is now possible to further improve the performance of the āinertā TMD basal plane <i>via</i> metal alloying, in addition to the previously reported strategies such as creation of point defects, vacancies and edges. The synthesis of graphene/W<sub>0.4</sub>Mo<sub>0.6</sub>S<sub>2</sub> produced at relatively low temperatures is scalable and could be used as an effective low cost Pt-free catalyst