Self-assembled single-crystalline GaN having bimodal meso/macropore structure to enhance photoabsorption and photocatalytic reactions.
ACS applied materials & interfaces(2019)
摘要
This paper describes the self-assembled fabrication of single-crystal GaN with a bimodal pore (meso/macropore) size distribution (BiPS-GaN). A 4.7 μm-thick BiPS-GaN layer was grown spontaneously using halogen-free vapor phase epitaxy in conjunction with boron impurity doping (> 1 × 10 atoms/cm) on a GaN template fabricated via metalorganic chemical vapor deposition (MOCVD-GaN). The boron impurity acted as a surfactant and its segregation generated a dense (> 1 × 10 cm), homogeneous distribution of mesopores with sizes of 30-40 nm in the GaN during growth. In addition, macropores with sizes of 0.1-2 μm were produced by the fusion of mesopores in close proximity to one another. As a result, the BiPS-GaN exhibited a high density of both meso and macropores, all aligned in the vertical direction (that is, along the c-axis). The BiPS-GaN was found to have a porosity of as high as 90% and showed good electroconductivity and almost the same high degree of crystallinity as the MOCVD-GaN template. Furthermore, the hybrid meso/macropore structure of the BiPS-GaN imparted excellent photoabsorption properties and allowed this material to work as an efficient support for a nanosized IrO catalyst. The photocurrent density in the BiPS-GaN was enhanced by as much as a factor of 10 compared to planar-GaN. Moreover, the oxygen generation efficiency of the BiPS-GaN with IrO catalyst was approximately doubled, compared to that of BiPS-GaN without IrO , while maintaining long-term stability. These results demonstrate that the BiPS-GaN fabricated in this facile manner has significant potential in applications such as photoelectrochemical reactions and catalysis.
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关键词
Gallium nitride,Porous material,Meso/macropore structure,Photoelectrochemical water splitting,Catalyst,Surfactant
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