| In the 21st century,where the energy crisis is emerging,the development and utilization of renewable energy is an important moment in the development of human destiny.Among many renewable energy sources,wind,solar and geothermal energy are developing steadily,but more attention is paid to the product of environmentally friendly hydrogen energy.Using renewable energy to generate electricity and living surplus electricity,hydrogen energy can be stored by electrolyzing water,which can then be used in fuel cell vehicles and gradually changing the global automotive energy use structure,reducing the consumption rate of fossil energy,and increasing the share of renewable energy,working hard to create a green world.For hydrogen energy,the preparation of hydrogen by electrolyzed water is an effective means.The current shortcoming is that the catalyst consumes too much energy,so further development of cheaper and more efficient catalysts is needed.The preparation of cheap and efficient catalysts is a constant pursuit in the fields of new energy,especially in the fields of hydrogen evolution reactions,oxygen reduction reactions,and lithium battery and so on.There are many reports on the preparation of electrode materials by recycling wastes,showing the environmentally friendly methods of recycling.In this paper,nitrogen-doped carbon-coated gold nanoparticles are prepared by microorganism in situ reduction of circuit board eluent.With structure characterization and properties of the catalysts are discussed in detail the method is simple and provides a new idea for waste recycling.Subsequently,the formation of carbon-coated,nitrogen-doped heterogeneous phase structure of molybdenum carbide nanosheets for high-efficiency hydreogen production is discussed.The activity changes and the distribution of active sites are also discussed in detail from computational simulations by studying nitrogen-doped ultra-thin molybdenum nanosheets and molybdenum disulfide nanosheets,providing comprehensive insights into the synthesis of N-atomic-doped electrocatalysts.Through careful analysis and discussion,the following conclusions are drawn:?1?The gold in the eluent of the circuit board is reduced in situ by microorganisms,and then the gold nanoparticle wrapped by nitrogen-doped carbon catalyst?Au@NC?is obtained by high-temperature calcination,which exhibits excellent performance in electrochemical hydrogen evolution reaction,with an initial potential of-54.1 mV,a Tafel slope of 76.8 mV dec-11 and good long-term test stability.The experimental results show that the high catalytic activity is mainly derived from the active gold nanoparticles formed by in situ reduction of microorganisms and the unique core-shell structure.The strong interaction between gold nanoparticles and carbon layer effectively regulates the charge distribution and adsorption ability of hydrogen on carbon layer.In general,the method utilizes the characteristics of environmental waste,and recycles and utilizes it to demonstrate a new way of recycling precious metal-rich wastes,providing an open mind for the preparation of efficient and inexpensive electrocatalysts.?2?By using molybdenum nanosheets reduced by commercially molybdenum oxide as precursors,and then mixing with dicyandiamide,followed by high temperature calcination,than the carbon-wrapped,nitrogen-doped heterogeneous phase structure molybdenum carbide nanosheets were synthesized and exhibited excellent performance in the electrochemical hydrogen evolution reaction.Overpotential is only 172 mV when current density is 10 mA cm-2,tafel slope is 60 mV dec-1,and has excellent long-term test stability.This experiment shows that the low-cost electrocatalysts for constructing molybdenum carbide with heterogeneous phase provide a new idea for the development of molybdenum-based electrocatalysts,which provides new references and inspiration for other researchers to develop new materials.?3?Combined with computational simulation method,the?001?surface model of sulfur-defects,nitrogen-doped molybdenum disulfide and?001?surface model of nitrogen-doped molybdenum carbide were constructed respectively,than the hydrogen adsorption free energy of possible adsorption sites on the surfaces were calculated.It is found that in molybdenum sulfide,some molybdenum atoms exposed due to the introduction of sulfur vacancies have excellent hydrogen adsorption energy,which is an effective way to increase the activity of molybdenum disulfide inert sulfur plane.At the same time,sulfur vacancies,doping of nitrogen atoms greatly improved the hydrogen adsorption ability of nearby sulfur atoms,thereby stimulating more active sites and increasing the intrinsic activity of molybdenum sulfide,while in molybdenum carbide,the surface of terminated with carbon atoms had stronger hydrogen adsorption ability.And it can provide more active sites of hydrogen adsorption.Similarly,the doping of nitrogen atom activates more active sites near the nitrogen atom,thus increasing the whole hydrogen evolution activity of catalyst after nitrogen doping.Through the above computational simulation analysis,it is considered that the doping of nitrogen plays an important catalytic promotion role in the molybdenum-based material,mainly reflecting the change of the charge density distribution on the surface of the catalyst,which in turn changes the hydrogen adsorption ability of the surface and enhance the performance of catalyst on HER. |
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