Modulating the structure of Cu in Cu2X/CNTs hollow tetrakaidecahedron to enhance high-efficiency H2O2 production.

Abstract

Regulation of active sites of electrocatalysts is critical in adjusting electronic structure and catalytic selectivity towards oxygen reduction reaction (ORR) to hydrogen peroxide (H₂O₂). Herein, the Cu₂X/CNTs (X = Se, SSe, S) hollow tetrakaidecahedron catalysts were synthesized to facilitate the electrocatalytic reduction of O₂ to H₂O₂. The introduction of S resulted in a shift from four-electron pathway on Cu₂Se/CNTs to two-electron process on Cu₂S/CNTs, ultimately leading to an enhancement in H₂O₂ productivity. Importantly, the addition of extra S species can modulate the chemical environment of active sites, and electrochemical tests demonstrate that the Cu₂S/CNTs catalyst exhibits an enhanced selectivity (over 91 %), production rate (360 mmol g_cat^-1 h^-1), and durability for H₂O₂ undergoing a two-electron process by an H-type electrolytic cell. The in-situ Raman spectroscopy result confirms that the structural stability of Cu₂S/CNTs during the reaction, and the accumulation of H₂O₂ increased with the extension of reaction time. Various experimental results and density functional theory (DFT) reveal that the S atoms can optimize the adsorption strength of the active sites to reaction intermediates, thereby creating an appropriate energy barrier for the formation of the determinant intermediate OOH* in H₂O₂ production, while maintain a high energy barrier for OO bond breaking of OOH* towards H₂O formation. This study proves insights into strategies for controlling H₂O₂ production and guiding the optimization of catalysts for H₂O₂ electrosynthesis.