Design Of Novel Inorganic Nanomaterials And Their Applications For Electrocatalytic Hydrogen Evolution/Carbon Dioxide Reduction

At present,energy and environment issues renain global problems to be solved urgently.To develop new environment-friendly altenlative energy will be the exclusive way.Hydrogen energy is regarded as one of the most potential ideal energy sources in the 21st century.As a carrier,hydrogen possesses the advantages of high energy density and no pollution.According to the World Hydrogen Energy Council,20%discount of C0Z emission in the global environment will depend on hydrogen by 2050,and hydrogen energy will account for up to 18%of the terminal energy demand.In view of this,people have been actively engaged in exploring and developing cost-effective hydrogen production strategies for decades Among them,electrolysis of water to produce hydrogen is an effective means to achieve industrialized and inexpensive production of pure hydrogen.However,there is currently a lack of efficient,inexpensive,and stable hydrogen evolution reaction(HER)catalystsOn the other hand,human's over-dependence on fossil fuels not only accelerates its depletion,but also leads to the excessive emission of greenhouse gas CO2.Over the past few decades,researchers have developed techniques to reduce CO2 in the atmosphere Among them,C0Z reduction technology can produce high value-added carbonaceous fuel while reducing carbon dioxide.Among 1any CO2 reduction technologies,electrocatalytic CO2 reduction(CO2RR)is considered to be an efficient "green" strategy,because it can effectively use the storable electricity generated by intermittent renexvable energy(such as solar,hydro and wind)to drive the reaction.However,electrochemical CO2RR currently faces many challenges,among which the biggest obstacle is the poor perfonnance of catalysts(such as low energy efficiency and poor product selectivity).Therefore,in order to fulfill the prolnise of electrochemical CO2RR in large-scale applications,it is essential to develop an economical,stable and efficient CO2RR catalyst.Given the current serious energy and environmental situation,the main research contents of this paper are as follows:1.Based on the fact that the free energy of hydrogen adsorption in molybdenum sulfide is slightly weak at the sulfided Mo edge and slightly strong at selenided Mo edge,the author expected to design a termary alloy material to continuously adjust the hydrogen adsorption free energy of the Mo edge by anion cloping,so as to achieve the regulation of HER performance.The high-temperature solution method was adopted to prepare ultra-thin MoS2(1-x)Se2x alloy nanoflakes with fully adjustable chemical composition and single or few layers.It was also proved that the introduction of selenium can continuously adjust the d-band electronic structure of-molybdenum,which may further adjust the hydrogen adsorption free energy,and ultimately further optimize the electrocatalytic activity of HER.In view of the generally similar nanoflake morphology of these two-dimensional transition metal dichalcogenide(TMDs)materials,the authors suggested that the improved properties reflect the higher intrinsic activity and hydrogen adsorption free energy closer to thermal neutrality of the alloy catalyst.This study provides a new idea for the design and optimization of high-performance HER catalysts in the future.2.Based on the success of the ternary alloys mentioned above,the authors further speculated that co-doping of anions and cations might achieve unexpected results.25 quaternary alloys of general formula of MoxW1-x(SySe1-y)2 were further prepared with a similar method in high yield.All products consisted of ultrathin nanoflakes in which the anion and anion components were independently adjustable throughout the scope of examination.When evaluated as an HER electrocatalyst in an acidic electrolyte,these materials exhibited high activity and durability,with a small onset overpotential and a Tafel Slope.In addition,the authors observed some general trends in their constitution-activity correlations.This study can provide valuable insights for the foture research on TMD-based high performance HER electrocatalysts.3.The incorporation of carbon interstitial atons into the early transition metal lattice increases the density of the d-band electronic states near the Fermi level,giving it platinum-like properties.People have been focusing on the study of WC.,however,the authors predicted by theory that W2C may be more active than WC.Nevertheless,how to prepare phase-pure,nonsintered,surface-clean W2C nanostructure to verify this theoretical conjecture is a formidable challenge.As shown in the W-C phase diagram,is not favored in thenmodynanics below 1,250?.In this paper,an improved carburizing method was developed to successfully prepare ultrasmall,phase-pure and surface-clean WZC nanoparticles for the first time.When evaluating its HER catalytic perfonnance,WZC nanoparticles showed exceptional electrochemical and photoelectrochemical(PEC)activity and stability,among which its electrocatalytic HER performance exceeded all existing WC-based materials,and PEC HER performance was comparable to that of pt-supported p-si.The results of the study highlight the great potential of this traditional non-popular material in HER electrocatalysis,and provide a valuable reference for the preparation of transition metal carbide nanomaterials.4.The authors reported that structural defects had a profound and positive effect on the selective CO-,RR to formate on Bi surfaces.In view of the low melting point and easy oxidation of bismuth,the authors first prepared Bi2O3 nanotubes with a fragmented outer surface.This unique structural feature provides a perfect template for the cathode conversion into highly defective metal Bi nanotubes(NTD-Bi).The proformance of COZRR to formate exceeded commercial requirements for the first time in flow cell.In addition,operando XAS and DFT theoretical calculations show that the abundant defective Bi site can stabilize*OCHO intermediate,which is the reason for its excellent activity and selectivity.Moreover,the coupling of the electrocatalyst with the Si photocathode also achieved high performance PEC CO2 reduction.It represents an important step forward to the commercialization of electrochemical CO2 utilization...