The solar water splitting is the third generation of solar energy utilizing technology for future energy problem. Hydrogen is a green fuel that does not generate carbon dioxide during combustion, which plays an important role in meeting the growing energy needs of the world. It is of great interest to utilize solar energy to produce hydrogen from renewable resources such as water.Several criteria should be satisfied to become a candidate semiconductor for water splitting. These are band gap, band edge, and solubility in aqueous solution. On the basis of these criteria, transition-metal dichalcogenides (TMDs), especially MoS2 and WS2, have recently received extensive attention. Despite the fact MoS2 and WS2 have a proper band gap which seems ideal for solar water splitting, MoS2 and WS2 alone have negligible photoelectrochemical activity. However, when MoS2 and WS2 are combined with reduced graphene oxide (rGO), it does exhibit photoelectrochemical activity toward hydrogen evolving reaction.In this study, we report the photoelectrochemical properties of free-standing MoS2/rGO and WS2/rGO hybrid foam. We synthesize MoS2 and WS2 by solvothermal process. At the same time, rGO foam is grown by immersion of Zn plates in GO solution. Reduced graphene oxide (rGO) foam plays important role of conducting framework to allow charge transportation. In solvothermal process, we could tune the nanostructures by altering precursors, temperatures, and concentrations. As a result, we found that photocurrent depends on the 3-dimensional nanostructure of MoS2/rGO and WS2/rGO foam. We could confirm our argument by measuring the IPCE and photocurrent as the nanostructure changed. Our results show that the absorption of visible light is dramatically varied by changing nanostructures and the electron transport in the rGO foam strongly depends on the local nanostructures. Based on our results, we will suggest that which nanostructure shows the best photoconversion efficiency.

Transition metal dichalcogenides loaded 3D nanoporous reduced graphene oxide foam for solar water splitting

248th National Meeting (2014)

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