Nanocarbon Electrocatalytic Oxygen Reduction Reaction

Hydrogen peroxide(H2O2)is a chemical reagent which is applied widely in practice.The usual way to generate H2O2 in the industry is the anthraquinone oxidation process,but this production process can be operated only at large scale and has problems in emitting exhaust gas and waste water.Compared to this process,the synthesis of H2O2 by electrochemical oxygen reduction reaction(ORR)is safer and more efficient.Due to the high cost of synthesis of metal catalysts,nonmetallic nanocarbon materials have been used in the electrocatalytic oxygen reduction to produce hydrogen peroxide due to their high richness and high electrochemical stability.In the process,adjusting the electrochemical oxygen reduction reaction pathway and increasing the H2O2production are the focus of research.In this paper,the nanocarbon black material is modified to obtain nanocarbon black materials with different oxygen contents and defects.The TEM shows that the framework structures of carbon black material have not be changed.The test result about the XPS data shows that the oxygen content increased with the raise of the oxidation temperature of the material.Then test the modified material as electroncatalysts in oxygen reduction reaction.The experimental results show that thermodynamics and kinetics performance of the oxygen reduction reaction has been improved with increse oxygen content of catalyst.The higher the oxygen content is more favourable of selectivity of the 2-electron oxygen reduction reaction(2e-ORR).The carboxyl functional group on the surface of the nanocarbon black material is the active site of the two-electron pathway.Highly selective electrosynthesis of H2O2 can be achieved by in situ electrostatic modulation of surface reaction over metal-free nanocarbon.In an alkaline electrolyte,the anionic surfactant has an inhibitory effect on the oxygen reduction reaction,while the cationic surfactant promotes the 2-electron oxygen reduction reaction to produce hydrogen peroxide.The cationic surfactant can act as a kinetic promoter for the oxygento-peroxide(O2P)reduction reaction over a carbon black(CB)catalyst,obtaining a percentage of peroxide production(%HO2-)over 95%.In the oxygen reduction reaction of nano carbon material as a catalyst,the cationic surfactant has a universal effect on the promotion of O2P.Surface carboxylates(-COOH)are found to be the main O2P reaction sites responsible for the remarkable peroxide selectivity under in situ Coulombic modulation by cationic surfactant.While the surface of material carbonyls(-C=O)also contributes peroxide generation,they exhibit the strong peroxide binding for subsequent electrocatalytic decomposition.The results of experiment further show that the lattice defects,saturated or unsaturated,is not the key contributor in the selective electrosynthesis.In chronoamperometry(CA)experiment,the carbon black-cationic surfactant system could deliver a 94%in%HO2 at a current density of 1.8 mA cm-2.