Synthesis of highly active black phosphorus photocatalyst from red phosphorus by solvothermal reaction
Akiyo Ozawa a b, Takuro Ashida b, Tomoko Yoshida c
a Osaka City University, Japan, Osaka, Japan
b Corporate Research Laboratories, Research & Development Division, Sakai Chemical Industry, Co., Ltd.
c Osaka City University, Japan, Osaka, Japan
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#SolFuel19. Solar Fuel Synthesis: From Bio-inspired Catalysis to Devices
Berlin, Germany, 2019 November 3rd - 8th
Organizers: Roel van de Krol and Erwin Reisner
Poster, Akiyo Ozawa, 398
Publication date: 18th July 2019

Photocatalytic water splitting have been attracted attention as one of solution to moderate global warming. Although various metal oxides have used as the photocatalyst, most of them could not work with visible light owing to their quite wide band gap. Recently black phosphorus has been studied as a candidate photocatalyst working under visible light. It is a layered semiconductor having a narrow band gap which could be altered by changing its layer thickness.[1] However, its synthesis is usually done at high temperature and pressure which makes the synthesis of large amount difficult. Tian et al. have employed solvothermal synthesis of black phosphorus nanosheets using white phosphorus and found that their synthesized nanosheet shows high photocatalytic activity for water splitting.[2] Unfortunately, their starting material, white phosphorus is difficult to handle because of spontaneously ignition in air at temperatures above 40 °C and toxify.

In this study, we have developed a solvothermal method using red phosphorus instead of white phosphorus to synthesize partially oxidized black phosphorus (BP) and investigated the formation mechanism. Synthesized BP nanoparticles were characterized with various methods, such as X-ray diffraction, Raman spectroscopy, scanning electron and transmission electron microscopies. P K-edge XANES spectra of the solvent after the synthesis indicated that some phosphorus materials were dissolved in it, suggesting a dissolution and deposition mechanism.

Synthesized BP showed the absorption edge around 850 nm in their UV-vis diffuse reflectance spectra and high photocatalytic activity on water splitting in methanol aqueous solution under visible light irradiation. In addition, we have found that morphology of black phosphorus depended on the used solvent type. We will show solvent effect on the morphology of BP, and discuss their photocatalytic activity and durability on water splitting in the conference.

This study was supported by JSPS KAKENHI Grant Number JP16H06440 (Synthesis of Mixed Anion Compounds toward Novel Functionalities).

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