Interface-Functionalized Hematite Nanocrystals for Oxygen Evolution

This report introduces a novel method for fabricating electrocatalysts, where hematite (α-Fe 2 O 3 ) is interface-functionalized with organic ligands to enhance the oxygen evolution reaction (OER). The synthesized samples feature nanoparticle morphology and crystalline structures consistent with hematite, known for its high stability among iron oxides. Functional groups from benzimidazole (bIm) and caffeine (Caf) act as scaffolds and sources of carbon, hydrogen, oxygen, and nitrogen, promoting metal–support interactions (MSIs) to boost OER activity and aid the formation of hematite nanocrystals. The optimal catalyst, Fe-(bIm)0.3Caf, is synthesized using a mix of ligands, mainly bIm with 30% Caf substitution. This combination introduces defects in the hematite structure, creating additional active sites and oxygen vacancies, which significantly improve OER performance. Fe-(bIm)0.3Caf exhibits the lowest overpotential (264 mV at 10 mA cm –2 ) and the smallest Tafel slope (30 mV dec –1 ) among all prepared samples and commercial Fe 2 O 3 . In contrast, commercial Fe 2 O 3 shows higher overpotential (331 mV at 10 mA cm –2 ) and lower durability under identical conditions in 1 M KOH over 30 h at room temperature. These findings underscore the importance of surface engineering of hematite nanocrystals to modify the surface and electronic structure, enhancing OER efficiency. This report also outlines a streamlined one-pot hydrothermal process for preparing interface-functionalized hematite nanocrystals at low temperatures, highlighting a promising approach for achieving efficient and durable electrocatalyst performance in driving the OER. The study emphasizes the crucial role of mixed ligands in enhancing OER efficiency in alkaline media.