Self-assembly of Ni 2 P nanowires as high-efficiency electrocatalyst for dye-sensitized solar cells
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esearch Letters
Self-assembly of Ni2P nanowires as high-efficiency electrocatalyst for dye-sensitized solar cells Qiwei Jiang, Yongcai Qiu, Keyou Yan, Junwu Xiao, and Shihe Yang, Department of Chemistry, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China Address all correspondence to Shihe Yang at [email protected] (Received 5 April 2012; accepted 11 July 2012)
Abstract We report an easy way to assemble porous one-dimensional (1D) Ni2P nanowires through phosphatization of a Ni(SO4)0.3(OH)1.4 nanobelt precursor. The peculiar synthetic process endows the Ni2P nanowires with large surface area, hierarchical porous structure and the ability to form closely connected network for transporting both electrons and electrolytes, which in conjunction with the high intrinsic electrocatalytic activity make it an excellent low-cost counter electrode material for dye-sensitized solar cells (DSSCs). Indeed, the first investigation of such novel counter electrode for DSSC presented superb photovoltaic performance rivaling the conventional Pt counter electrode.
Introduction As one of the most important components in dye-sensitized solar cells (DSSCs), the noble metal platinum is often used as counter electrode because of its superior electrocatalytic activity, high electrical conductivity as well as good chemical stability.[1] In view of the limited reserve and high cost of Pt, it is highly important to search for less expensive Pt-free counter electrode alternatives with a similarly high electrocatalytic activity for future development of DSSCs. In recent years, various low-cost alternatives to platinum in DSSCs have been investigated,[2] including carbon materials,[3,4] conducting polymers,[5,6] transition metal nitrides,[7,8] sulfides,[9,10] carbides,[11] oxides[12,13] and most recently phosphide.[14] But seldom included in all these materials, except for carbon materials, are one-dimensional (1D) nanostructures. In principle, the electrocatalytic activity of Pt-alternative materials is not only related to their intrinsic electronic structure but also related to their structure and morphology. Typically, a highly efficient counter electrode of DSSC needs to have a large surface area, high electrical conductivity and an open structure for accommodating and rapidly transporting electrolyte of iodide/ tri-iodide.[7] Usually, a large surface area comes with more grain boundaries between the nanoparticles, a feature that can hinder electron transport. In this sense, 1D nanomaterials such as nanowires and nanotubes are advantageous due to the possibility of having both high electrical conductivity and superior electrocatalytic activity. The porous Ni2P nanowires reported here represent a glaring example of such 1D nanomaterials. Transition metal phosphides are known to have noble metallike catalytic activity, good electrical conductivity and high chemical stability. The purpose of this work was to develop a
new strategy to synthesize 1D nanomaterial of Ni2P and explore its use as DSSC counter electrode. To this en
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