Single Yttrium Atom Is Fixed On Porous Carbon-coated Titanium Dioxide For Electrocatalytic Nitrogen Reduction

With the progress of mankind,the development of society nowadays is increasingly dependent on the environment and resources,so it must be sustainable.Hot topics in today’s era are:use renewable energy to create highvalue chemicals under environmentally friendly conditions.It is well known that ammonia is an important chemical raw material and has been widely used in fertilizers,fibers,explosives,etc.In addition,ammonia can also be used as a(HED)high energy density and carbon-free energy carrier.At present,ammonia is mainly produced by the Haber-Bosch process in industry.It is synthesized under high temperature and high pressure,resulting in high energy loss and serious greenhouse effect.The electrocatalytic nitrogen reduction reaction is an environmentally friendly way to convert nitrogen into ammonia under normal temperature and pressure conditions.It has become the most likely alternative to the Haber-Bosch method,and has recently attracted widespread attention.Although exciting progress has been made,due to the high bond energy of the nitrogen-nitrogen triple bond(941 kJ mol-1),it is difficult to interrupt under normal temperature and pressure,and due to the occurrence of hydrogen evolution reaction in aqueous solution.The ammonia yield and Faraday efficiency are not ideal,and there are still great difficulties and challenges in the industrial application of electrocatalytic nitrogen reduction.At present,electrocatalysts are mainly concentrated on precious metal-based catalysts,so there is an urgent need to find a catalyst that is cheap and easy to obtain,has high efficiency,good performance,and high stability.Single-atom catalysts(SAC)have unique advantages.Isolated single-atom sites can maximize the use of atomic efficiency.It is expected to become the most promising catalyst in the future.Single-atom catalysts can significantly increase the yield of ammonia and Faraday effectiveness.We synthesized single yttrium atoms isolated on porous carbon-coated TiO2(denoted as Y-TiO2-C)through a simple hydrothermal method and annealing in an Ar(ESI(?))atmosphere.In 0.1 M HCl electrolyte of synthesis of single Y site under room temperature and atmospheric pressure NRR into NH3,is greatly enhanced by using high resolution TEM,XPS,XRD,Raman,BET characterization methods of catalysts for the catalytic activity analysis,the results show that under the condition of environment this unit catalyst under the condition of low electric potential has a strong N2 adsorption force and can effectively use N2 electric catalytic synthesis of NH3.We use a three-electrode electrochemical device under normal temperature and pressure,and 0.1 M HCl as the electrolyte for electrocatalytic ammonia synthesis test.At-0.22 V(vs.RHE),the ammonia production reaches the highest 6.3 μg h-1 mgcat.-1,The Faraday efficiency is 11.2%.After a 30 hour long-term electrolysis test,the current density remains stable.Better than many electrocatalysts in the literature.We have performed DFT calculations,and we have compared the free energy of formation of*NNH as △G(*NNH),because the formation of*NNH is a potential determination step(PDS)in a variety of catalysts.△G(*NNH)Press Y@C4(1.67 eV)<Y@C3(1.73 eV)<Y@TiO2(2.45 eV)<TiO2(110)(2.64 eV)in order of increasing*NNH is about 1 eV less than TiO2(110)on Y@Cx,Y@Cx is more stable than TiO2(110).It shows that the Y@Cx position is beneficial to the activation of N2.Investigate the origin of increasing NRR activity at a single Y site.The complete reaction free energy of NRR also shows the excellent catalytic activity of Y@CX position,Y@C4(1.55 eV)<Y@C3(1.58 eV)<Y@TiO2(2.22 eV),a single yttrium atom embedded in the carbon layer It is considered to play an important role in improving the performance of NRR.