Metal–organic framework–carbon composite (NH2-UiO-66/Printex L6) for boosted hydrogen peroxide electrogeneration

Abstract

Metal organic frameworks (MOF) are promising materials for use as electrocatalyst modifiers due to their unique properties, particularly their large surface area and tunable chemical structure. In this study, Printex L6 carbon (PL6C) was modified with NH2-UiO-66 MOF (Zr-MOF) at different loadings (1–5% w/w) to enhance the selectivity and efficiency of the hydrogen peroxide (H2O2) electrogeneration. The synthesized material was thoroughly characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) analyses, confirming the successful synthesis of the Zr-MOF. The carbon samples modified with Zr-MOF were first electrochemically characterized, and studies under hydrodynamic conditions using the rotating ring-disk electrode (RRDE) technique were carried out to evaluate the effect of modification on H2O2 selectivity and 2e− ORR activity. As a result, the Zr-MOF-modified carbon exhibited higher selectivity than the pristine PL6C, reaching 94.7% and 95.5% for 1% and 3% loadings, respectively. However, at a higher modification level (5%), a significant decrease in selectivity was observed, achieving only 71.8%. Subsequently, the 1% Zr-MOF/PL6C material was further compared with PL6C by different physicochemical techniques. Finally, a gas diffusion electrode (GDE) based on 1% Zr-MOF/PL6C was produced, and its performance toward the 2e-ORR was compared with that of the unmodified PL6C GDE at different current densities. At 25 mA cm−2, the 1% Zr-MOF/PL6C GDE exhibited superior performance, achieving a Faradaic efficiency of 34.1% and an energy consumption of 16.2 kWh kg−1, outperforming the pristine electrode. These results demonstrate that the incorporation of MOFs into carbonaceous materials is an effective strategy to enhance H2O2 electrogeneration while maintaining moderate energy consumption, highlighting MOF–carbon hybrids as a promising approach for developing more efficient electrocatalysts for the 2e− ORR.