Modulation of electron distribution and intermediate adsorption by C–O–Si sites for efficient oxygen reduction and lithium storage

Abstract

Biowaste-derived heteroatom-doped porous carbons have garnered substantial attention as nonmetal catalysts for electrocatalysis. However, various heteroatom species and/or diverse coordination states within the carbon framework complicate the understanding of their enhanced catalytic activity. This study employs hydroxyl-rich biomass, specifically banana peels, and photovoltaic waste SiCl₄ as precursors to synthesize porous carbon featuring highly uniform C–O–Si bonds. This material facilitates the elucidation of mechanisms underlying the improved oxygen reduction activity of C–O–Si active sites. Due to Si's substantially lower electronegativity (1.90) compared to that of O (3.44), Si atoms exhibit lower electron density and possess Lewis basicity. This characteristic allows Si to function as a novel active site, enhancing the oxygen reduction activity. The resulting Si–BP–Carbon catalyst demonstrates a low half-wave potential of 0.813 V (vs. RHE) and achieves a diffusion-limited current density of 4.69 mA cm⁻², coupled with good tolerance to methanol crossover and high selectivity toward the 4-electron reaction pathway. Density functional theory calculations corroborate that Si atoms can lose electrons in C–O–Si bonds, improving the adsorption of O₂ and *OOH intermediates. The abundance of C–O–Si bonds makes Si–BP–Carbon highly suitable as an anode material for lithium-ion batteries due to its enhanced capacity for lithium-ion (Li⁺) adsorption facilitated by Si heteroatoms.