Enhanced electrocatalytic H₂O₂ production using Ar jet plasma-polymerized trimethoxyphenylsilane forming Lewis acid sites

The rising demand for hydrogen peroxide (H₂O₂) has driven interest in electrocatalytic ORR due to the environmental impact of the anthraquinone process. Ar jet plasma treatment on trimethoxyphenylsilane (TMPS)-coated carbon felt (CF) led to varying polymerized TMPS (P-TMPS) formations. An optimized 15-min Ar jet plasma-treated TMPS-loaded CF (CF-S₁₀-P₁₅) electrode consistently produced H₂O₂ at ∼1.8 % over 5 hrs across five cycles. Solid-state attenuated total reflectance (ATR)-Fourier transform infrared spectroscopy (FTIR), carbon-13 and hydrogen-1 (¹³C/¹H) nuclear magnetic resonance spectroscopy (NMR), temperature-programmed desorption (TPD) of ammonia, X-ray photoelectron spectroscopy (XPS), and in situ Raman analyses indicated that the isolated silanol (Si-OH) functional group was crucial for the ORR, significantly enhancing H₂O₂ yield. ATR-FTIR confirmed Si-OH sites as Lewis acid sites, while XPS showed a linear correlation of Si³⁺/Si_total and O_ads/O_total ratios with H₂O₂ production. ¹³C/¹H NMR revealed plasma treatment time influences TMPS polymerization, with mature Si–OH polymerization at 15 min. In situ Raman analysis indicated Si–O electron transfer, facilitating •OOH reduction to H₂O₂ under potential. Time-lapse ATR-FTIR captured •OOH and •O₂^– intermediates on CF-S₁₀-P₁₅ during ORR, elucidating the H₂O₂ generation mechanism. Optimizing P-TMPS on CF via Ar jet plasma yielded a cost-effective electrode for efficient H₂O₂ production.