Molybdenum Disulfide As A Cocatalyst For Photocatalytic Hydrogen Production

Loading a cocatalyst for hydrogen evolution reaction on a photocatalyst can lower the overpotential of hydrogen evolution, effectively promote the separation of photogenerated electrons and holes, and improve the efficiency of photocatalytic system. Thus, studies on the cocatalyst have attracted people’s attention. In this paper, MoS2 as cocatalyst modified with CdS/rGO and dye-sensitization of MIL-125(Ti), the photocatalytic properties were studied.In the first part, photodeposition of MoS2 in different pH of TEOA aqueous solution on rGOx/CdS,which was prepared by a solvothermal method, prepared MoS2-CdS/rGO-y to study the photocatalytic hydrogen evolution. Followed with the characterizations and tests such as X-ray diffraction analysis,transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy,infrared spectroscopy. It was found that the hydrogen production activity of MoS2-CdS/rGO-11(photodeposition at pH=11) is 4.3 times as high as MoS2-CdS/rGO-7(photodeposition at pH=7). At low pH 7, MoS2 deposits on the surface of the CdS particles of the composite. However, at high pH 11, it loads on the exposed rGO. When MoS2 is on the rGO, the transfer of the photoexcited electron from CdS to rGO is compatible with the HER at MoS2(synergic effect), whereas the transfer is incompatible with the HER when it is on the CdS(antisynergic effect). Moreover, the MoS2 deposited on the CdS decreases the photoabsorption of CdS, and the effect is avoided when MoS2 is on the rGO.In the second part, MIL-125(Ti) was prepared by a solvothermal method, followed with the characterizations and tests such as UV-Vis diffuse reflectance spectroscopy,X-ray diffraction analysis,infrared spectroscopy.Using TEOA(pH=7) aqueous solution as electron donors, and EY as a sensitized agent, the photocatalytic hydrogen evolution was studied. When MoS2 loading molar content is 7%, the catalyst has the highest activity(18 μmol/ h). When absent of MoS2, the catalyst has the almost no activity. The cause for enhanced activity is that MoS2 can promote the effective separation of photoproduced electrons and holes.