Preparation And Hydrogen Evolution Reaction Of Iron Doped Molybdenum Sulfide&Iron Sulfide-Molybdenum Sulfide Composite

Along with the rapid depletion of fossil fuels and the consequences of environmental pollution, the requirements and development of clean energy is becoming increasingly important. Hydrogen is attractive and often considered as a clean energy carrier alternative to exhaustible resource. It is well known that the conventional methods for hydrogen production often require enormous energy, so it is urgent to explore a new hydrogen production method which is more energy-efficient. The electrochemical hydrogen evolution reaction(HER) from water has become a hotspot in sustainable hydrogen production. On this basis, people focus on the study of HER catalysts, such as the precious metal-Pt, it has excellent catalytic performances. However, these precious metal catalysts limited by their expensive value and scary, so how to develop a relatively low-cost and efficient catalyst has become a main target. Transition metal sulfides show great potential on HER, it is also becoming a hot topic today.In this paper, we focused on how to enhance the HER catalytic performances on the basis of MoS2,including through doping Fe into MoS2 and composite FeS with MoS2 to improve the catalytic performances. At the same time, the catalysts were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS) and Inductively Coupled Plasma(ICP) to analyze the structural characteristics. We also obtained the polarization curves, tafel slope and electrochemical impedance parameters to analyze the HER performances of the catalyst.First, we improved the catalytic performances of MoS2 by doping Fe. Through the situ synthesis method, we prepared the Fe-doped MoS2. We also explored the effects of Fe precursor, solvent, reaction time, reaction temperature and the ratio of Mo:Fe in the experiment. We found that, using the ferrocene,sulfur powder and molybdenum carbonyl as raw materials, Xylene as solvent, at 220°C, 24 h conditions,the obtained Fe-doped MoS2 catalyst has the best catalytic performances. In this case, the catalyst showa low tafel plot of 64mV·dec-1, a low over potential of ~-234 mV at-10mA·cm-2, a large current density of-375mA·cm-2 at-0.7V. In the meantime, the double-layer capacitance(Cdl) reached 13.7mF·cm-2,which means the catalyst has good catalytic performances. It is the main reason that Fe make the MoS2 crystal lattices distorted in the process of Fe-MoS2 synthesis, and increase the number of bridged S22-.The increase of S22-indicates that the catalytic active sites of MoS2 raises, which improve the catalysts performances.Then, we improved the catalytic performances by composite MoS2 with FeS. In the experiment, we explored the influences of Fe precursor, solvent, reaction time, reaction temperature and the ratio of Mo:Fe. We found that, using the ferrocene as Fe precursor, DMF as solvent, at 180 °C, 7h conditions,the obtained FeS/MoS2 catalyst has the best catalytic performances. In this case, the catalyst show a low tafel plot of 53mV·dec-1, a low over potential of ~-238 m V at-10mA·cm-2, a large current density of-367mA·cm-2 at-0.7V. In the meantime, the Cdl reach 12.5mF·cm-2,which means the catalytic performances is relatively good. It is the main reason that FeS has intrinsic catalytic performances,when it composite with MoS2, the synergistic effect between FeS and MoS2 will be occur. It increases the number of bridged S22- in MoS2, then improves the catalytic performances.Finally, we improved the catalytic performances of above two catalysts by introduce the C precursors. In the experiment, we mainly explored the effects of C precursors species, surfactant and other factors in the synthesis process. We found that, the catalytic performances of Fe-MoS2/C is not ideal, but the FeS-MoS2/GO exhibits good catalytic performances. In this case, the catalyst show a low tafel plot of 50mV·dec-1, which indicates that the catalyst has a faster rate of hydrogen evolution reaction, the catalyst also exhibits a low over potential of ~-234 mV at-10mA·cm-2, a large current density of-436mA·cm-2 at-0.7V. In the meantime, the Cdl reach 20.9mF·cm-2, which means the catalyst have a good catalytic activity. In the impedance test, we found that GO reduces the impedance of the composite catalyst, and it is good for catalyst’s conductibility. It is the main reason that catalytic performances of FeS-MoS2/GO exhibit a enhancement.Through optimizing experiment conditions, we prepared Fe-doped MoS2, FeS-MoS2 and FeS-MoS2-Go catalysts. After the structure characterization and performance testing, we find these catalysts exhibit excellent catalytic activity than MoS2 for hydrogen electrolysis reaction, it also has acertain theoretical and practical significance to the synthesis of HER catalysts.