Preparation Of TiO₂/C Electrode Catalysts By Surface Electronic State Control And Study On Synthesis Of H₂O₂

Hydrogen peroxide(H₂O₂)is one of the most significant and fundamental industrial chemicals for several frontier fields including environment,agriculture,and energy.[1]Currently,World Health Organization(WHO)has listed H₂O₂as the crucial disinfectant against SARS-Co V-2 that causes the COVID-19 pandemic.Therefore,the electrocatalytic synthesis of hydrogen peroxide(H₂O₂)driven by renewable energy under natural conditions is a direct synthesis method that may replace the traditional high-energy anthraquinone process.It enables on-site and decentralized H₂O₂production using air and renewable electricity for various applications.Recent advances in catalyst preparation technology have made great achievements,but efficient and stable inexpensive electrocatalysts for the synthesis of H₂O₂ are still urgently needed.Transition metal oxides are usually considered not to be effective catalysts for the electrocatalytic synthesis of H₂O₂,and they are more likely to select for the generation of H₂O.In fact,the catalytic activity of transition metal oxides for ORR depends on the interaction between the d-band center of the transition metal and the p-band denter of the oxygen intermediate.Titanium dioxide as an electrocatalyst suffers from poor electrical conductivity and few intrinsic active sites,etc.In this article,the selectivity and activity of H₂O₂ were improved through the construction of core-shell structure,oxygen functional coupling,nitrogen element doping construction defects,rare earth element doping and the electronic regulation of amorphous/crystalline heteroconjugated on the d-band center of Ti O₂.The specific studies are as follows:1.Preparation of core-shell structure precursors by alcohol-thermal method,formation of core-shell structure Ti O₂/C by high temperature roasting,tuning up the conductivity and exposure of active sites of Ti O₂.Multi-scale optimization of Ti O₂ by sulfuric acid for particle and size,specific surface area,and oxygen functional groups.The high selectivity and activity of the electrocatalyst for H₂O₂ was attributed to the in-situ preparation of core-shell Ti O₂/C to improve its electrical conductivity and promote the exposure of active sites and coupling of oxygen functional groups.2.N-doped core-shell Ti O₂/C hybrid electrocatalyst was successfully prepared in situ by alcohol-thermal method and high-temperature roasting step.N-doped carbon materials can improve the selectivity and activity of H₂O₂.N-doped Ti O₂ builds defect sites and improves the conductivity of Ti O₂.XPS proved that N-doping changed the electronic structure of Ti O₂ and reconstructed the active center and electron transfer channel.The main reasons for the high selectivity and activity of 200 N-Ti O₂/C for H₂O₂ is(1)core-shell structure fully exposes the active site;(2)N-doping changes the the d-band center of Ti O₂.Ti O₂ and reconstructs the transfer channel;(3)The type and content of N doping.3.11 rare earth element-doped core-shell Ti O₂/C electrocatalysts were prepared by the Kirkendall effect using the unique 4f electronic property of rare earth elements to change the the d-band center of transition metals.It was demonstrated by XPS that the doping of rare earth elements could change the d-band center of transition metals and reconstruct the active centers and fast electron transfer channels.The core-shell structure fully exposes the active sites and the mesoporous structure is beneficial to accelerate the mass transfer process and improve the catalytic kinetics,which in turn improves the stability of the catalyst.Due to the number and arrangement of the outermost electrons of different rare earth elements,the selectivity and activity of the electrocatalyst for H₂O₂ vary greatly.4.Amorphous/crystalline heterojunction catalysts with core-shell structure were prepared by using the characteristics of unsaturated electron configuration of amorphous materials.It was demonstrated by XPS and TEM that amorphous Ti O₂ and Co S₂ form a heterojunction,providing strong electron interactions on both sides of the interface.XPS proves that electrons at the interface transfer from Co S₂ to amorphous Ti O₂,and the charge transfer channel is reconstructed.On the other hand,the rearrangement of interfacial electrons increases the density of amorphous Ti O₂ electron cloud,which is conducive to the adsorption of O₂ and electron transfer to O₂,thus improving the catalytic performance and stability of the electrocatalyst.In this article,the d-band center distribution of transition metal was changed by means of oxygen functional groups,element doping and the construction of amorphous/crystalline heterojunction.The relationship between the d orbital electron distribution of transition metal Ti and the performance of electrocatalyst was studied in depth.It is expected to provide reference for the design of highly selective and active catalysts for the synthesis of H₂O₂.