| Hydrogen energy is considered as one of the most promising clean energy sources in the 21 st century because of its green,non-polluting and renewable nature.Among the many methods for hydrogen production,the environmentally clean electrolytic hydrogen precipitation reaction has received a lot of attention from many researchers.It is important to develop economical,efficient and durable electrocatalysts for hydrogen precipitation.Noble metal electrocatalysts usually have good hydrogen precipitation activity,among which the best performance is platinum-based catalysts,however,the high cost of platinum greatly limits the industrial application.Therefore,it is particularly important to improve the efficiency of platinum atom utilization and to explore cheap alternatives to platinum.Single-atom catalysts maximize the efficiency of metal atom utilization,but the inherent activity of single-atom catalysts still leaves much room for improvement.In addition,the relatively inexpensive ruthenium-based catalysts with similar binding strength to hydrogen(65 kcal·mol-1)and stable electrocatalytic hydrogen precipitation activity in alkaline environments have the potential to be used as a new generation of hydrogen precipitation electrocatalysts,stimulating our research interest.The main research work is summarized as follows:(1)The MoS2-loaded single-atom Pt high-activity hydrogen precipitation electrocatalyst(Pt SAS/MoS2)was successfully prepared by hydrothermal method guided by the results of DFT theoretical calculations.Spherical aberration corrected transmission electron microscopy(HAADF-STEM)showed that Pt was dispersed on MoS2 in the form of single atoms.The electronic and coordination structures of Pt SAs/MoS2 were analyzed by X-ray absorption fine structure spectroscopy,which showed that the Pt coordination environment was single and close to zero valence,again demonstrating that Pt was dispersed on MoS2 in the monoatomic form.was only 36 mV,which was significantly more active than that of commercial Pt/C(overpotential of 42 mV);the Tafel slope was 27 mV·dec-1,which was lower than that of commercial Pt/C at 36 mV·dec-1,indicating a higher kinetics of hydrogen precipitation.In addition,comparing the MoS2 hydrogen precipitation catalysts loaded with Pt in the form of nanoparticles(Pt NPs/MoS2),the electrocatalytic hydrogen production activity and stability were found to be significantly lower than that of Pt SAs/MoS2.indicating the advantage of single-atom loading.(2)RuSx@C catalysts with different Ru contents were synthesized using 4,5ethvlenedithio-1,3-dithiol-2-thione as precursors.The electrocatalytic hydrogen production performance study revealed that RuSx@C-4 catalysts with high Ru loading(-4 wt%)exhibited excellent electrocatalytic hydrogen production activity and stability in both acidic and alkaline solutions.25 mV overpotential(42 mV for commercial Pt/C)was achieved at a current density of 10 mA·cm-2 in 0.5 M H2SO4 solution;the Tafel slope The very low Tafel slope of 24.6 mV·dec-1(36 mV·dec-1 for commercial Pt/C)indicates its excellent electrocatalytic hydrogen production activity.1.0 M KOH solution,RuSx@C-4 still has a very high electrocatalytic hydrogen production activity with an overpotential of only 22 mV(56 mV for commercial Pt/C)and a Tafel slope of 30.0 mV·dec-1(31.2 mV·dec-1 for commercial Pt/C),indicating faster kinetics of RuSx@C-4 HER.DFT calculations demonstrate that S doping modulates the electronic structure of Ru,optimizes the adsorption energy of hydrogen atoms and water on Ru,promotes the decomposition of water,and thus increases the hydrogen precipitation activity. |
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