Lab talk
Jul 4, 2012
Bent substrate enhances water splitting
Flexible plastic substrates have shown great potential when applied to photovoltaic cells, but their use in photoelectrochemical applications has yet to be fully investigated. To explore the idea, researchers from Nanyang Technological University, Singapore, and the Institute of Materials Research and Engineering, A-Star, both in Singapore, have fabricated a silver-decorated ZnO nanorod array on a bent flexible substrate. The hybrid structure was then used as a photoanode for splitting water to produce hydrogen. In the work, the team noticed that improved photoelectrochemical (PEC) properties were achieved upon bending the substrate.
The team prepared silver-decorated ZnO nanorod arrays on polyethylene terephthalate (PET) substrates via low-temperature hydrothermal growth followed by electron beam evaporation of silver. The short circuit current density (JSC) and the photo-electron conversion efficiency (PCE) were largely improved for the silver-decorated ZnO nanorod arrays on bent substrates compared with those on flat ones. Maximum values for JSC and PCE were achieved when the silver film thickness and substrate bending radius were 10 nm and 6.0 mm, respectively.
Multiple reflections
To fully understand the reasons behind the result, the researchers carried out systematic studies on the morphologies, structures and optical properties of silver-decorated ZnO nanorod arrays on a bent substrate. It was found that at a combination of silver film thickness=10 nm and bending radius=6.0 mm , the silver-decorated ZnO nanorod arrays were able to trap and absorb the most light. The team attributes these enhanced capabilities to the multiple reflections from the bent substrate, and the plasmonic effect of the silver film.
A full description of the study can be found in the journal Nanotechnology.
About the author
This collaborative study was conducted by an interdisciplinary research team from Nanyang Technological University (NTU) and the Institute of Materials Research and Engineering (IMRE), both in Singapore. Wei Yuefan is a PhD student at NTU. She is currently working on improving the properties of the photoelectrochemical (PEC) cells based on metal oxides for hydrogen generation. She performed the synthesis process, structural, morphological, optical and PEC analysis. Kong Junhua is a research associate at NTU, who is working on energy-storage applications of one-dimensional hybrid nanostructures. He performed the structural and morphological analysis. Jiao Zhihui is also a PhD student at NTU, who supported the optical analysis. Dr Ke Lin is a research scientist at IMRE, who has a strong interest in solar-energy PEC cells for hydrogen production and guided this project. Dr Liu Hong is also a research scientist at IMRE, who performed the silver coating by electron beam evaporation. Prof. Lu Xuehong is an associate professor at NTU and has a particular interest in polymer nanocomposites and nanostructural organic-inorganic hybrid materials. Prof. Du Hejun is an associate professor at NTU and has a great interest in miniaturized smart sensors and actuators, as well as micro-electro-mechanical system. Prof. Sun Xiao Wei is a full professor at NTU, and his research interests focus on wide bandgap semiconductors including GaN and ZnO, organic electronics and display technologies. Profs. Du and Sun supervised the whole project.
