3D Co sub(3)(PO sub(4)) sub(2)-Reduced Graphene Oxide Flowers for Photocatalytic Water Splitting: A TypeII Staggered Heterojunction System

• Published in: ChemSusChem 2016-11, Vol.9 (22), p.3150-3160
• Main Authors: Samal, Alaka, Swain, Smrutirekha, Satpati, Biswarup, Das, Dipti Prakasini, Mishra, Barada Kanta
• Format: Article
• Language: English
• Subjects: Catalysts; Graphene; Heterojunctions; Hydrogen; N-type semiconductors; Oxides; Photocatalysis; Three dimensional flow
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201601214

The design, synthesis, and photoelectrochemical characterization of Co sub(3)(PO sub(4)) sub(2), a hydrogen evolving catalyst modified with reduced graphene oxide (RGO), is reported. The 3D flowerlike Co sub(3)(PO sub(4)) sub(2) heterojunction system, consisting of 3D flowerlike Co sub(3)(PO sub(4)) sub(2) and RGO sheets, was synthesized by a one-pot insitu photoassisted method under visible-light irradiation, which was achieved without the addition of surfactant or a structure-directing reagent. For the first time, Co sub(3)(PO sub(4)) sub(2) is demonstrated to act as a hydrogen evolving catalyst rather than being used as an oxygen evolving photoanode. In particular, 3D flowerlike Co sub(3)(PO sub(4)) sub(2) anchored to RGO nanosheets is shown to possess dramatically improved photocatalytic activity. This enhanced photoactivity is mainly due to the staggered typeII heterojunction system, in which photoinduced electrons from 3D flowerlike Co sub(3)(PO sub(4)) sub(2) transfer to the RGO sheets and result in decreased charge recombination, as evidenced by photoluminescence spectroscopy. The band gap of Co sub(3)(PO sub(4)) sub(2) was calculated to be 2.35eV by the Kubelka-Munk method. Again, the Co sub(3)(PO sub(4)) sub(2) semiconductor displays n-type behavior, as observed from Mott-Schottky measurements. These RGO-Co sub(3)(PO sub(4)) sub(2) conjugates are active in the visible range of solar light for water splitting and textile dye degradation, and can be used towards the development of greener and cheaper photocatalysts by exploiting solar light. Catalyst in bloom: A type-II heterojunction photocatalyst based on 3D flowerlike Co sub(3)(PO sub(4)) sub(2) on reduced graphene oxide (RGO) nanosheets is synthesized through a photoreduction route. The heterojunction has the unique property of generating hydrogen through photosplitting of water, unlikely the activity of pristine Co sub(3)(PO sub(4)) sub(2).