Defects in Porous Networks of WO3 Particle Aggregates

• Published in: ChemElectroChem Vol. 3; no. 4; pp. 658 - 667
• Main Authors: Márquez, Augusto, Rodríguez-Pérez, Manuel J., Anta, Juan A., Rodríguez-Gattorno, Geonel, Bourret, Gilles R., Oskam, Gerko, Berger, Thomas
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.04.2016; John Wiley & Sons, Inc
• Subjects: aggregation; Defects; doping; mesoporous materials; thin films; tungsten
• ISSN: 2196-0216; 2196-0216
• DOI: 10.1002/celc.201500435

The most frequently studied functionalities of porous WO3 particle systems—namely their electrochromic and photocatalytic properties—are intimately related to the wanted or unwanted action of defects in the material. Here, we report on the generation and action of three types of defects in WO3 electrodes: solid/solid interfaces between adjacent particle aggregates, defects generated in situ upon photoinduced electron accumulation, and defects resulting from tungsten bronze formation. Depending on the degree of aggregate interconnection, we observe a beneficial, albeit transient, effect of charge accumulation on the photoelectrocatalytic activity of the thin films, giving rise to an almost threefold increase in photocurrent. The dynamic change of thin film properties associated with this doping process is tracked by a combined spectroscopic and electrochemical approach, which allows the beneficial and detrimental effects of defects to be resolved on the electrochemical potential scale. The good and the bad: Defects generated in situ in a working WO3 photoelectrode significantly influence its performance. Moderate electrochemical doping may lead to a threefold increase of the photocurrent. Complete loss of the photoelectrocatalytic activity is observed upon strong doping (see figure). The impact of defects on performance depends on the quality of particle/particle contacts in the mesoporous thin film.