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Preparation of Core–Shell‐Structured Nanoparticles (with a Noble‐Metal or Metal Oxide Core and a Chromia Shell) and Their Application in Water Splitting by Means of Visible Light
Author(s) -
Maeda Kazuhiko,
Sakamoto Naoyuki,
Ikeda Takahiro,
Ohtsuka Hajime,
Xiong Anke,
Lu Daling,
Kanehara Masayuki,
Teranishi Toshiharu,
Domen Kazunari
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201000616
Subject(s) - photocatalysis , noble metal , water splitting , materials science , visible spectrum , oxide , nanoparticle , non blocking i/o , zinc , metal , valence (chemistry) , inorganic chemistry , photocatalytic water splitting , nanotechnology , catalysis , chemistry , metallurgy , optoelectronics , biochemistry , organic chemistry
Core–shell‐structured nanoparticles, consisting of a noble metal or metal oxide core and a chromia (Cr 2 O 3 ) shell, were studied as promoters for photocatalytic water splitting under visible light. Core nanoparticles were loaded by impregnation, adsorption or photodeposition onto a solid solution of gallium nitride and zinc oxide (abbreviated GaN:ZnO), which is a particulate semiconductor photocatalyst with a band gap of approximately 2.7 eV, and a Cr 2 O 3 shell was formed by photodeposition using a K 2 CrO 4 precursor. Photodeposition of Cr 2 O 3 on GaN:ZnO modified with a noble metal (Rh, Pd and Pt) or metal oxide (NiO x , RuO 2 and Rh 2 O 3 ) co‐catalyst resulted in enhanced photocatalytic activity for overall water splitting under visible light ( λ >400 nm). This enhancement in activity was primarily due to the suppression of undesirable reverse reactions (H 2 –O 2 recombination and/or O 2 photoreduction) and/or protection of the core component from chemical corrosion, depending on the core type. Among the core materials examined, Rh species exhibited relatively high performance for this application. The activity for visible‐light water splitting on GaN:ZnO modified with an Rh/Cr 2 O 3 core–shell configuration was dependent on both the dispersion of Rh nanoparticles and the valence state. In addition, the morphology of the Cr 2 O 3 photodeposits was significantly affected by the valence state of Rh and the pH at which the photoreduction of K 2 CrO 4 was conducted. When a sufficient amount of K 2 CrO 4 was used as the precursor and the solution pH ranged from 3 to 7.5, Cr 2 O 3 was successfully formed with a constant shell thickness (≈2 nm) on metallic Rh nanoparticles, which resulted in an effective promoter for overall water splitting.