Noble-Metal-Free Catalysts For Efficient H₂O₂ Electrosynthesis

Hydrogen peroxide（H₂O₂）is an important chemical product which has large proportion of active oxygen.As a green oxidizer,hydrogen peroxide has been widely used in many fields,such as chemical synthesis,paper bleaching,wastewater treatment,disinfection,and fuel cells.In 2015,the output of hydrogen peroxide has reached 5.5million tons,and its demand is growing rapidly.However,the widely used anthraquinone method has the disadvantages of high energy consumption and high pollution,moreover,requires the use of hydrogen.The above disadvantages are not consistent with the concept of green development and sustainable development.By contrast,the two-electron oxygen reduction reaction（2e^-ORR）does not require the use of hydrogen,while protons in water can be utilized instead as the source of hydrogen to achieve the production of hydrogen peroxide driven by electricity.The process of 2e^-ORR is environmental-friendly and energy-saving,which has great development potential.Thermodynamically,oxygen tends to convert to water during the ORR process,so it is necessary to design suitable electrocatalysts to achieve efficient electrosynthesis of hydrogen peroxide.Hydrogen peroxide has strong oxidation,good stability and broad application in acidic environment,but it is challenging to develop stable and efficient 2e^-ORR catalysts in acidic media.By contrast,the oxidation and stability of hydrogen peroxide under alkaline conditions are weak,which limit its application.Therefore,it is of great scientific significance and practical value to explore the practical application of basic 2e^-ORR.In this paper,the2e^-ORR catalytic performance of nickel and carbon-based materials in acidic and basic media was investigated respectively,and the practical application of basic 2e^-ORR was explored:（1）A series of nickel chalcogenides（Ni Se₂,Ni S₂ and Ni O）were prepared as acidic 2e^-ORR catalysts,and their performance of H₂O₂ electrosynthesis under acidic conditions was investigated.The results show that Ni Se₂ has the best catalytic performance,excellent selectivity and great stability.The relationship between the electronic state of the central metal,the type of anionic ligand and the adsorption energy of intermediates was also investigated,and the idea of regulating the 2e^-ORR properties by anion regulation was proposed.（2）The commercial carbon black was heat treated at varied temperatures and examined by electrochemical test.The influence of heat treatment temperature on material’s morphology,structure and element composition was investigated.500-CB was determined to be the optimal catalyst,which showed excellent 2e^-ORR performance on both rotating ring disk electrode and gas diffusion electrolytic cell.The experiment also achieved the production of high concentration hydrogen peroxide（5.56%）by adjusting the concentration of electrolyte,and finally extracted Na₂CO₃·1.5 H₂O₂ from the electrolyte,which explored the path of practical application of hydrogen peroxide electrosynthesis under basic conditions.