Semiconductor nanomaterials are used in various applications such as solar cell, hydrogen generation, CO2 catalytic reduction and organic pollutant degradation with the aim of generating energy. He et al. (2016) proposed the preparation of amorphous/crystalline Si incorporated ZSGO/ZGSO nanowires with tunable band structure and optimized photoelectrochemical PEC performance. Their work was published in ACS NANO.
PEC water splitting can generate energy by converting solar energy into clean hydrogen energy. Zn2GeO4, TiO2 and ZnO are the commonly studied photoelectric semiconductor application, this is due to the wide bandgap (3.2 – 4.5eV), and are generally in a crystalline state. Investigations on amorphous semiconductors show limitation in characterization, photoelectric application and preparation. This limitation has led to development of strategic means in realization of high efficiency energy generation and storage of amorphous semiconductors. Elemental manipulation at the atomic level will change the intrinsic bonding environment of atom in a material. The researchers planted some transition elements (Mn, Co, Zn) and nonmetal element (N, C, and B) into semiconductor materials as heteroatoms to narrow the bandgap and improve the light harvesting.
The manipulation involves replacing Zn2+ and Ge4+ with Si2+ and Si4+ during the ions-alternative-deposition IAD process, respectively, where Si2+ and Si4+ were derived from the stepwise oxidation of a Si foil by adsorbed or dissolved O2 in reaction solution. The research team pointed that the substitution of Si heteroatoms led to a narrowed bandgap for amorphous ZSGO nanowires yet a widened bandgap for crystalline ZGSO nanowires, compared with pure ZGO. PEC water-splitting testing showed that the amorphous ZSGO nanowires exhibited a significantly enhanced performance, such as higher photoelectric efficiency, and more stable photo response, compared with crystalline ZGSO and ZGO nanowires. The performance enhancement is ascribed to the advantages of the amorphous ZGSO nanowire arrays such as a narrower bandgap, lower fluorescence and higher specific surface area that enable a higher light harvesting capability, lower charge recombination, and more active catalytic sites.
Researchers found that Si heteroatoms in ZSGO nanowires suffer much higher bonding distortion and induce stronger structure tension relative to that of ZGSO nanowires. The subtle bonding distortion in ZGSO nanowires enables the preservation of the crystalline structure. The amorphous ZSGO nanowire arrays also display a significantly enhanced photocurrent that is almost twice that of its crystalline counterpart of the ZGSO nanowire arrays. These results demonstrate that the ZSGO nanowire arrays can serve as a promising photocatalyst for highly efficient PEC devices. They observed a stronger absorption in the ultraviolet waveband for the ZSGO nanowire arrays than the ZGSO/ZGO nanowire powders, the team attributed it to accessibility of ZSGO to light entrance and harvesting.
The ZSGO amorphous nanowire arrays can be employed as an efficient, stable, and fast-response photocatalyst for photoelectric applications. This study may offer an opportunity for the development of amorphous materials with desirable structure and property for promising applications.
Ting He2,3, Lianhai Zu1, Yan Zhang1, Chengliang Mao5, Xiaoxiang Xu1, Jinhu Yang*1,3, Shihe Yang*4, Amorphous Semiconductor Nanowires Created by Site-Specific Heteroatom Substitution with Significantly Enhanced Photoelectrochemical Performance, ACS Nano, 2016, 10 (8), pp 7882–7891.Show Affiliations
- School of Chemical Science and Engineering,Tongji University, Shanghai 200092, R. China.
- School of Materials Science and Engineering,Tongji University, Shanghai 201804, R. China.
- Research Center for Translational Medicine & Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital,Tongji University School of Medicine, No. 150 Jimo Road, Shanghai 200120, R. China.
- Department of Chemistry,The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong R. China.
- Key Laboratory of Pesticide & Chemical Biology of Ministry of Education, Institute of Environmental Chemistry, College of Chemistry,Central China Normal University, Wuhan 430079, R. China.
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