Surface Regulation Of Low-Dimensional Inorganic Materials For The Electrochemical Conversion Of Small Molecules

With increasing energy crisis,expanding energy demands and global warming brought up by the use of fossil fuel,development of future energy has become the focal point of society.It is crucial to develop sustainable,fossil-free strategy to cover the production of global necessary fuel and chemical product.The exploitation of new energy storage and conversion system could realize the reduction of carbon dioxide emissions while maintain the supply of raw materials of daily products.Therefore,recent studies have proposed that the development of electrochemical conversion technology combined with the conversion of energy-related molecules such as water and carbon dioxide in the atmosphere into valuable products may be a development direction with great potential in the future.Energy-related applications in electrocatalytic reactions involve two main energy cycles:water cycle and carbon cycle.Among them,hydrogen evolution reaction(Hydrogen Evolution Reaction,HER),oxygen evolution reaction(Oxygen Evolution Reaction,OER),and oxygen reduction reaction(Oxygen Reduction Reaction,ORR)are the core of the water cycle.On the other hand,capture and direct use of carbon dioxide could be achieved through electrochemical conversion reactions.Compared with biochemical conversion or photochemical conversion methods,electrochemical conversion can better reduce carbon dioxide emissions.This energy conversion method has higher efficiency and can operate under milder environmental conditions.Electrocatalytic water splitting,oxygen reduction and carbon dioxide reduction reactions all involve heterogeneous catalysis.Therefore,the catalytic performance could be greatly influenced by the surficial physical and chemical properties of the catalyst.Therefore,designing efficient surface control strategies is an important factor in promoting the application of clean energy technology.In the past few decades,many efforts have been devoted to the surface modulation of catalysts.A large number of research suggested that surface control strategies can maintain the bulk structure of the catalyst while realizing the regulation of the intrinsic properties of the catalytic active sites on the material surface,thereby simultaneously achieving high bulk phase conductivity and high stability retention and the optimization of surface site electronic structure and catalytic activity.The specific content of this paper is as follow:(1)Electrochemical surface reduction is an effective strategy to achieve catalyst surface reconstruction.In this paper,Co3O4 nanowires are used as the model material,and the low-valence CoO active layer is constructed by electrochemical surface reduction in an alkaline electrolyte to realize the dual modulation of increased surface active area and the generation of active substances,and then realize improved catalytic performance of OER reaction.In addition,this electrochemical surface reduction strategy can be further extended to other spinel-type transition metal oxide catalysts and the construction of three-dimensional electrodes.In this chapter,we propose that the electrochemical surface reduction strategy can be used as means of regulating the surface of catalytic materials,which has universal applicability to spinel-type oxide materials.Our work provides new ideas for the design of high-efficiency OER catalyst materials,and provides new insights for the study of reaction mechanisms.(2)Surface doping is one of the important strategies for surface regulation of lowdimensional inorganic solid catalysts.In this paper,SnS2 nanosheets are used as model materials,and N2 plasma technology is used to achieve surface N atom doping.Thanks to the strong electronegativity of N atoms,there is a certain degree of charge transfer between the surface Sn atoms and N atoms.Thus,the surface Sn atoms present positive charge.This Sn?+ structure is beneficial to the formation and stability of*HCOO intermediates in the electrocatalytic carbon dioxide reduction reaction,thereby achieving significantly improved yield and selectivity of formate.Compared with the original sample,the N-rich Sn nanosheets(N-Sn(S)nanosheets)prepared by the surface nitrogen injection process exhibited 5 times the current density and 2.45 times the faradaic efficiency.In addition,this surface nitrogen injection project has been proved to be equally applicable to CuS and In2S3 materials.In this chapter,we propose that the surface nitrogen injection project provides a new way to design highly efficient electrocchemical carbon dioxide reduction catalysts.(3)Electrochemical surface reorganization is an effective method of surface and interface control of low-dimensional inorganic solid catalytic materials.This control strategy can simultaneously achieve the introduction of active sites and optimization of surface microenvironment for electrocatalytic oxygen reduction reaction.In this chapter,we use Co2N nanowires as a model material,and construct a CoOOH active layer rich in Pt clusters on the Co2N surface by electrochemical surface oxidation in Pt contained electrolyte.Pt clusters are concerned as the active sites in ORR catalytic process and the CoOOH active layer promotes proton transport and coupling in the catalytic process.The Pt cluster-modified surface microenvironment-regulated Co2N nanowires(PtSMO-Co2N nanowires)exhibit superior ORR catalytic performance.Under neutral conditions,its half-wave potential exhibits an increase of 365 mV and 92 mV compared to the original Co2N nanowires and commercial Pt/C.In addition,this Pt-SMO-Co2N nanowire material can be used as a cathode material for a neutral rechargeable zinc-air battery,and its energy density can reach 67.9 mW/cm2.In this work,we propose that the synergistic optimization of intrinsic activity of the active site and the microenvironment are an effective way to prepare highly efficient electrocatalysts for oxygen reduction reaction.