Regulating the Local Reaction Microenvironment at Chromium Metal–Organic Frameworks for Efficient H2O2 Electrosynthesis in Neutral Electrolytes

Abstract

The electrochemical synthesis of hydrogen peroxide represents a promising alternative to the traditional anthraquinone process, aiming for zero pollution. However, achieving efficient electrochemical synthesis of hydrogen peroxide in neutral electrolytes is challenging due to the sluggish kinetics of the two-electron oxygen reduction reaction. To address this issue, a unique metal–organic framework (MOF) featuring Cr metal sites coordinated with tetrabromoterephthalic acid (Cr-TBA) is synthesized. This specially designed MOF exhibits a distinctive paper-clip-like structure and remarkably enhanced Lewis acidity. Experimental results demonstrate that the obtained structure can facilitate the attraction of OH⁻ ions in solution, promoting their accumulation on the catalyst surface. This enhancement leads to excellent performances of Cr-TBA in neutral electrolytes, achieving Faradaic efficiencies of 96–98% and a production rate of 13.4 mol g_cat⁻¹ h⁻¹ at the current density of 150 mA cm⁻². Operando spectroscopy and density functional theory calculations indicate that this modified microenvironment effectively facilitates the conversion of the ^*OOH intermediates to H₂O₂ on the catalyst surface.