Facile Templateless Fabrication of a Cobalt Oxyhydroxide Nanosheet Film with Nanoscale Porosity as an Efficient Electrocatalyst for Water Oxidation

• Published in: ChemPhotoChem 2018-03, Vol.2 (3), p.332-339
• Main Authors: Chandra, Debraj, Tanaka, Kou, Takeuchi, Ryouchi, Abe, Naoto, Togashi, Takanari, Kurihara, Masato, Saito, Kenji, Yui, Tatsuto, Yagi, Masayuki
• Format: Article
• Language: English
• Subjects: artificial photosynthesis; cobalt oxyhydroxide; nanostructure engineering; templateless synthesis; water oxidation catalyst
• ISSN: 2367-0932; 2367-0932
• DOI: 10.1002/cptc.201700200

The development of efficient catalysts for water oxidation is widely required because the efficiency of fuel production by artificial photosynthesis is severely limited by the sluggish kinetics of water oxidation. A unique CoO(OH) nanosheet (CoO(OH)‐NS) film having porosity in nanoscale dimensions has been synthesized by a facile electrochemical technique without the assistance of any template. The SEM image exhibited that the film is composed of nanosheets that are well scattered and formed uniformly by unidirectional vertical growth on the electrode surface. The TEM image showed a highly porous nanostructure with randomly oriented nanopores (with a dimension of ca. ≤5 nm) inside the nanosheet. The HRTEM image revealed that flat‐shaped rectangular CoO(OH) nanocrystals (ca. 2–3 nm) were randomly stacked together to form the nanosheet and interspaces between the nanocrystals for the nanoporous structure. The specific surface area of the CoO(OH)‐NS film was 92 m2 g−1, which is higher than that (43 m2 g−1) of a CoO(OH) nanoparticle (CoO(OH)‐NP) film that is prepared by a chemical procedure as a reference sample. A superior electrocatalytic performance for water oxidation was observed for CoO(OH)‐NS electrode compared with the CoO(OH)‐NP electrode. This result originates from the large accessible surface‐to‐volume ratio of the unique porous nanosheet structures, which provides a large number of electroactive water oxidation sites at the electrolyte−CoO(OH) interface. No template needed: A CoO(OH) nanosheet film with nanoscale porosity has been synthesized by a facile electrochemical technique without the assistance of a template. The material demonstrated superior electrocatalytic performance for water oxidation compared to a reference electrode composed of a CoO(OH) nanoparticle film.