Surface Modification Of Carbon-based Materials For Electrochemical Synthesis Of H₂O₂ Through Oxygen Electrochemistry

As one of the most important chemical substances,hydrogen peroxide（H₂O₂）has attracted extensive attention all over the world.At present,energy-intensive anthraquinone method is mainly used in industrial production of H₂O₂.This method has many processes and produces a large number of waste by-products.Morover,the produced H₂O₂ needs further purification.At the same time,centralized production mode has high cost in long-distance transportation and long-term storage due to the instability of H₂O₂.Therefore,it is urgent to develop an environmentally friendly,efficient and low-cost in-situ H₂O₂ production method.One direct synthesis of H₂O₂ can be achieved through H₂ and O₂ in the presence of catalysts.However,the mixture of H₂ and O₂ could be easily explode.The efficient production of H₂O₂ by electrochemical oxygen reduction reaction（ORR）has attracted people’s attention.In recent years,a large number of catalyst materials for electrochemical preparation of H₂O₂ have been reported.So far,the catalysts with the best performance have been reported for the synthesis of precious metals and their alloys such as Au,Pt and Pd,but their high price and scarcity hinder their commercial application.Carbon-based materials have the characteristics of abundant earth reserves,low cost and unique surface morphology and structure that can be regulated.After proper treatment,the performance of carbon-based materials can be comparable to that of noble metal catalyst,which has become a hot research topic in the electrosynthesis of H₂O₂catalyst.Therefore,this paper mainly studied the effect of surface functionalization treatment of carbon-based catalyst on the performance of electrochemical preparation of H₂O₂.The main contents are as follows:1.By rapid kneading oxidation,oxidized carbon nanotubes（O-CNTs）rich in oxidizing functional groups were obtained within 2 hours.The optimal sample O-CNT-7 showed excellent electrocatalytic performance for electrochemical preparation of H₂O₂ in alkaline environment.O-CNTs-7 has a high onset potential（0.74 V vs.RHE）,and has about 90%H₂O₂selectivity in a wide potential window of 0.3-0.7 V vs.RHE,and H₂O₂ yield reaches 191 m M g^-1_cata h^-1 at 0.4 V vs.RHE potential.In-situ infrared attenuated total reflection（ATR-IR）spectra shows the relationship between the adsorption behavior of HOOH,_ad and OOH,_ad and the potential of O-CNT-7 during the reaction,which confirms the two-electron association pathway of O-CNT-7.This study provides a general method for the preparation of carbon-based catalysts with rich oxygen-containing functional groups on the surface for the electrosynthesis of H₂O₂.2.In order to further improve the conversion efficiency of oxygen reduction O₂-to-H₂O₂and obtain a two-electron oxygen reduction catalyst with higher activity,the defective carbon nanotubes loaded with Au nanoclusters（Au-OCNTs）were prepared.The optimized Au-OCNTs-150 has the best electrocatalytic activity,the selectivity of H₂O₂ is up to 96%,and the H₂O₂yield is up to 370 m M g^-1_catah^-1.As a carrier,the defective carbon nanotubes can promote the uniform dispersion of Au nanoclusters,providing more active sites for their further application in electrochemical reactions.The morphology and structure of the catalyst materials are analyzed and electrochemical tests are carried out.The intermediate states and synthesis paths of H₂O₂ are investigated by electrochemical in-situ infrared spectroscopy（ATR-IR）.The synergistic effect of Au nanoclusters and oxygen-containing functional groups on the catalyst surface is also discussed.3.In order to solve the problem of environmental pollution caused by oxidation treatment with acid,a more environmentally friendly surface modification method of carbon material was explored.A high active two-dimensional blade catalyst with cavity structure（O-ZLCN）was prepared by hydrothermal oxidation combined with strong oxidation of H₂O₂ itself.Hydrothermal oxidation introduces abundant defects and oxygen-containing functional groups on the surface of the catalyst,and O-ZLCN-6 showed the best electrocatalytic performance with95%H₂O₂ selectivity in the wide potential window of 0.3-0.7 V vs.RHE in alkaline medium.The yield of H₂O₂ at 0.5 V vs.RHE potential reaches 285 m M g^-1_cata h^-1,at 0.65 V vs.RHE potential mass activity is 144.2 A g^-1,comparable to most high-performance two-electron oxygen reduction catalysts.In order to explore the possible reaction intermediates and products during oxygen reduction on O-ZLCN-6 and the transformation path of H₂O₂ synthesis in 0.1 M KOH solution,in-situ ATR-IR spectroscopy was used to track the dynamic process of o-ZLCN-6 active center.It provides reference for the preparation of more green,environmental protection,low cost and high activity carbon-based materials two-electron oxygen reduction catalyst.