Surface states modulation of hematite photoanodes for enhancing photoelectrochemical catalysis

Associating Physical and Photocatalytic Properties of Recyclable and Reusable Blast Furnace Dust Waste

Blast furnace dust waste (BFDW) proved efficient as a photocatalyst for the decolorization of methylene blue (MB) dye in water. Structural analysis unequivocally identified α-Fe2O3 as the predominant phase, constituting approximately 92%, with a porous surface showcasing unique 10-30 nm agglomerated nanoparticles. Chemical and thermal analyses indicated surface-bound water and carbonate molecules, with the main phase's thermal stability up to 900 °C. Electrical conductivity analysis revealed charge transfer resistance values of 616.4 Ω and electrode resistance of 47.8 Ω. The Mott-Schottky analysis identified α-Fe2O3 as an n-type semiconductor with a flat band potential of 0.181 V vs. Ag/AgCl and a donor density of 1.45 × 1015 cm-3. The 2.2 eV optical bandgap and luminescence stem from α-Fe2O3 and weak ferromagnetism arises from structural defects and surface effects. With a 74% photocatalytic efficiency, stable through three photodegradation cycles, BFDW outperforms comparable waste materials in MB degradation mediated by visible light. The elemental trapping experiment exposed hydroxyl radicals (OH•) and superoxide anions (O2-•) as the primary species in the photodegradation process. Consequently, iron oxide-based BFDW emerges as an environmentally friendly alternative for wastewater treatment, underscoring the pivotal role of its unique physical properties in the photocatalytic process.

Surface Oxygen Species in Metal Oxide Photoanodes for Solar Energy Conversion

Converting and storing solar energy directly as chemical energy through photoelectrochemical devices are promising strategies to replace fossil fuels. Metal oxides are commonly used as photoanode materials, but they still encounter challenges such as limited light absorption, inefficient charge separation, sluggish surface reactions, and insufficient stability. The regulation of surface oxygen species on metal oxide photoanodes has emerged as a critical strategy to modulate molecular and charge dynamics at the reaction interface. However, the precise role of surface oxygen species in metal oxide photoanodes remains ambiguous. The review focuses on elucidating the formation and regulation mechanisms of various surface oxygen species in metal oxides, their advantages and disadvantages in photoelectrochemical reactions, and the characterization methods employed to investigate them. Additionally, the article discusses emerging opportunities and potential hurdles in the regulation of surface oxygen species. By shedding light on the significance of surface oxygen species, this review aims to advance our understanding of their impact on metal oxide photoanodes, paving the way for the design of more efficient and stable photoelectrochemical devices.