Study On The Surface And Interface Tuning Of P Region Metal-Based Catalysts And Electrochemical CO₂ Reduction Reaction

The excessive emission of CO₂ has broken the earth ecological balance and directly endangers the living environment of human beings.CO₂ is the most abundant C₁ resource in environment.Artificial CO₂ utilization is one of the most effective ways to solve the environment and energy problems.Electrochemical CO₂reduction reaction（e CO₂RR）is a promising approach for the sustainable development of energy and environment,because of the advantages of mild reaction conditions,green process,adjustable products and high efficiency.However,there are still some key scientific problems and challenges toword e CO₂RR,such as 1)the efficient adsorption and activation of CO₂ molecule on catalyst surface,2)selective regulation of high value-added products,3)reaction mechanism and precise controling.Herein,a series of p-region metal-based catalysts by surface and interface tuning strategy（such as oxygen vacancy engineering,multiple active center strategy,carrier effect ect.）,have been constructed.The structure-activity relationship and mechanism of e CO₂RR were explored to improve the catalytic activity and selectivity of e CO₂RR.The main research contents of this thesis are as follows:（1）To improve the activation ability of CO₂ on catalyst surface,an oxygen vacancy engineering strategy was propsed to construct V_o-rich SnO₂ catalysts by H₂ thermal etching.The V_o-rich SnO₂ catalysts possess unique electronic structure,which can improve the CO₂ activation and suppress HER to reduce overpotential and improve selectivity.V_o-rich SnO₂ exhibits the C₁ Faraday efficiency（FE）of 92.5%at a current density of-44.2 m A cm^-2,which is remarkably higher than those of pristine SnO₂.And it has high catalytic stability for 30 h.（2）The oxygen vacancy on the surface of SnO₂ is conducive to anchoring the metal active site.A series of Metal-V_o-SnO₂ catalysts with multiple active centers were synthesized by loading Zn,Ag,Bi or In on the surface of V_o-SnO₂ to tuning the selectivity of catalysts.Theoretical calculation shows that different Metal-V_o-SnO₂interface has different adsorption advantages for*COOH or*OCHO key intermediates.Ag-V_o-SnO₂ can decrease the adsorption energy barrier of*COOH and improve CO selectivity.Bi-V_o-SnO₂ has an adsorption advantage on*OCHO and tends to form HCOOH.After optimizing the loading capacity,Ag-V_o-SnO₂-2 exhibits a CO FE of95.3%.Bi-V_o-SnO₂-2 exhibit a HCOOH FE of 91.4%.In addition,the strategy is universal.Zn-V_o-SnO₂ and In-V_o-SnO₂ also exhibit higher selectivity for single products in the range of-0.6 to-1.2 V.（3）M-MO type catalysts with multiple active centers can regulate the e CO₂RR selectivity.A facile preparation of Pd-modified SnO₂ nanosheets catalysts（Pd-SnO₂NSs）for efficient syngas production with widely tunable H₂/CO ratios was developed.With the increasing of Pd-SnO₂ interface,the e CO₂RR to HCOOH pathway is suppressed.Pd-SnO₂ NSs display high activity,as well as desirable current density and stability for CO₂ reduction to CO.4.3Pd-SnO₂ NSs exhibit H₂/CO ratios range from 4.2to 0.28 at the applied potentials vary from-0.5 to-1.1 V and long durability of 30 h.（4）To increase current density,the conductive carbon components with high HER active sites are usually introduced into catalysts.A inside-mode strategy was presented to synthesize an indium oxide/carbon nanotubes compound（MWCNTs@In₂O₃）by taking advantage of the self-organizing characteristics of In-based metal–organic frameworks（MIL-68）to embed carbon nanotubes into the indium oxide shell.MWCNTs@In₂O₃ can inhibit the active sites of HER induced by MWCNTs,and improve the current density and selectivity of catalysts.MWCNTs@In₂O₃exhibits a HCOOH FE of 92.2%at-1.1 V.（5）In addition,Sn/Sb or Bi/In multi-active center catalysts were constructed by using ultra-thin GO nanosheets or Cu foam as conductive carriers,respectively,to realize the highly selective preparation of HCOOH by e CO₂RR.In the large-size ultrathin dual-active sites Sn_x-Sb_y-O-GO NSs catalysts,Sb active site can assist water activation for forming unique*H species,and promoting the binding strength of*OCHO key intermediates on catalyst surfaces,thereby boosting the selectivity for HCOOH over CO.The optimized Sn₇-Sb₃-O-GO NSs exhibit an excellent HCOOH FE of 96.5%and long durability over 21 h.In the Bi-In alloy catalysts system,the alloy effect can improve the sharp increase of HER activity of single metal catalyst under high current density.In the range of-0.9 to-2.2 V and-20 to 180 m A cm^-2,Bi-In@Cu-foam exhibits a FE_HCOOH above 85%,and the highest FE_HCOOH=92.3%.