Nitrogen-doped vertical graphene for highly efficient hydrogen peroxide electrosynthesis in acidic environment
Ding Zhang, Constantine Tsounis, Lingyi Peng, Hang Yin, Furqan Hussain, Michael Carnell, Alexander Macmillan, Dewei Chu, Rose Amal, Zhaojun Han
Abstract
• A triple-phase interface (TPI) was created on the hydrophobic N-VG-PDMS catalyst. • High Faradaic efficiency and high productivity were obtained for H 2 O 2 production. • Microscopic techniques unveiled a stable TPI microenvironment during the reaction. • The stable TPI simultaneously enhanced gas diffusion and local pH values. Electrochemical oxygen reduction (ORR) through a two-electron (2e − ) pathway offers a green route for on-demand production of hydrogen peroxide (H 2 O 2 ), which is an industrially valuable chemical as well as a renewable energy carrier. Metal-free carbon-based materials have been exploited as promising catalysts for H 2 O 2 generation; however, they often exhibit poor performance with low productivity under acidic conditions. Herein, a nitrogen-doped vertical graphene catalyst is developed with a stable hydrophobic solid–liquid-gas three-phase interface (TPI) enabled by polydimethylsiloxane (PDMS) coating. The catalyst exhibits a high Faradaic efficiency (FE) of ∼ 80 % across a wide potential range from 0 to −0.6 V vs. reversible hydrogen electrode (RHE) at a maximum current density of 140 mA cm −2 , resulting in a remarkably high H 2 O 2 productivity of 21 mol g catalyst −1 h −1 in acid. Furthermore, a high concentration of H 2 O 2 up to 10,500 ppm is obtained with the FE maintained at ∼ 75 %. Confocal laser scanning microscopy (CLSM) and fluorescence lifetime analysis reveal that the hydrophobic TPI increases gas diffusion and local pH value to enhance both activity and selectivity towards H 2 O 2 . This work provides valuable insights into the rational design of metal-free carbon-based catalysts for efficient H 2 O 2 generation.