Mesoporous α-Fe2O3 thin films synthesized via the sol―gel process for light-driven water oxidation

• Published in: Physical chemistry chemical physics : PCCP Vol. 14; no. 38; pp. 13224 - 13232
• Main Authors: HAMD, Wael, COBO, Saioa, SANCHEZ, Clement, FIZE, Jennifer, BALDINOZZI, Gianguido, SCHWARTZ, Wilfrid, REYMERMIER, Maryse, PEREIRA, Alexandre, FONTECAVE, Marc, ARTERO, Vincent, LABERTY-ROBERT, Christel
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2012
• Subjects: Catalysis; Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Condensed Matter; Electrochemistry; Exact sciences and technology; General and physical chemistry; Materials Science; Physics; Porous materials; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Water; Photoelectrochemistry; Binary compound; Iron oxide; Film; Hydrogen; Doping; Temperature effect; X ray; Potential; Porous material; Thin film; Template; Electrodes; pH; Photoelectron spectrometry; Oxidation; Dip coating; Low temperature; Hematite; Scanning electron microscopy; Annealing; Transition element compounds; Air; X ray diffraction; Mesoporosity; Impregnation; Chemistry; Sol gel process; Electrochemistry; Catalyst
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c2cp42535a

This work reports a facile and cost-effective method for synthesizing photoactive α-Fe(2)O(3) films as well as their performances when used as photoanodes for water oxidation. Transparent α-Fe(2)O(3) mesoporous films were fabricated by template-directed sol-gel chemistry coupled with the dip-coating approach, followed by annealing at various temperatures from 350 °C to 750 °C in air. α-Fe(2)O(3) films were characterized by X-ray diffraction, XPS, FE-SEM and electrochemical measurements. The photoelectrochemical performance of α-Fe(2)O(3) photoanodes was characterized and optimized through the deposition of Co-based co-catalysts via different methods (impregnation, electro-deposition and photo-electro-deposition). Interestingly, the resulting hematite films heat-treated at relatively low temperature (500 °C), and therefore devoid of any extrinsic dopant, achieve light-driven water oxidation under near-to-neutral (pH = 8) aqueous conditions after decoration with a Co catalyst. The onset potential is 0.75 V vs. the reversible hydrogen electrode (RHE), thus corresponding to 450 mV light-induced underpotential, although modest photocurrent density values (40 μA cm(-2)) are obtained below 1.23 V vs. RHE. These new materials with a very large interfacial area in contact with the electrolyte and allowing for a high loading of water oxidation catalysts open new avenues for the optimization of photo-electrochemical water splitting.