Mesoporous thin film WO 3 photoanode for photoelectrochemical water splitting: a sol–gel dip coating approachReport as inadecuate

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* Corresponding author 1 MHN - Matériaux Hybrides et Nanomatériaux LCMCP - Laboratoire de Chimie de la Matière Condensée de Paris 2 LCBM - UMR 5249 - Laboratoire de Chimie et Biologie des Métaux 3 LA2M - Laboratoire d-Analyse Microstructurale des Matériaux 4 SRMA - Service des Recherches Métallurgiques Appliquées DMN - Département des Matériaux pour le Nucléaire : DEN-DMN 5 Total Energies Nouvelles 6 Helmholtz-Zentrum Berlin - Helmholtz-Zentrum Berlin für Materialien und Energie GmbH

Abstract : A facile and cost-efficient method to fabricate a mesoporous structured WO3 photoanode was implemented for use in a tandem dual water splitting photoelectrochemical cell. Semi-transparent thin films of tungsten trioxide were fabricated by sol-gel process, incorporating a block co-polymer to induce a template-directed mesoporous structure. These thin films are deposited by dip coating onto transparent conducting oxide substrates and crystallized at a low temperature of 400°C in air. These thin film photoanodes exhibit a photocurrent of up to 0.6 mA-cm² in potassium phosphate buffers of pH 2, 4, and 6 at 1.23 V vs. RHE under 300 mW-cm² visible 400 – 900 nm light irradiation with a faradic efficiency of up to 75%. Furthermore, we have demonstrated that corrosion occurs in electrolytes of pH > 4. The faradic efficiencies in varying pH solutions however suggest that parasitic redox reactions occurs in acidic conditions, limiting the O2 production and demonstrating the need for stable surface co-catalysts to increase faradic efficiencies. In neutral conditions, protective layers and-or co-catalysts are needed for increasing WO3 photoanode stability.

Author: Samantha Hilliard - Guido Baldinozzi - Dennis Friedrich - Stéphane Kressman - Henri Strub - Vincent Artero - Christel Laberty-Ro



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