Monodispersed Nickel Phosphide Nanocrystals in Situ Grown on Reduced Graphene Oxide with Controllable Size and Composition as a Counter Electrode for Dye-Sensitized Solar Cells
Song Wang, Ying Xie, Keying Shi, Wei Zhou, Zipeng Xing, Kai Pan, Andreu Cabot
Abstract
Owing to their abundance, low cost, and excellent functional properties and catalytic activity, transition metal phosphides (TMPs) have been proposed in a broad range of energy conversion technologies. However, their challenging synthesis and moderate electrical conductivity have limited their implementation in real applications. Here, we detail a simple procedure to grow fully dispersed nickel phosphide nanocrystals (NCs) with controlled size, phase, and composition on the surface of reduced graphene oxide (rGO). The resultant NixPy/rGO composites effectively combine a huge density of catalytically active sites from NixPy with the excellent conductivity of rGO, thus exhibiting highly improved electrocatalytic activities. NixPy/rGO composites were tested as the counter electrode (CE) in dye-sensitized solar cells (DSSCs), providing significantly improved performance over conventional Pt-based CEs. The incorporation of CEs based on Ni12P5/rGO composites allowed reaching a power conversion efficiency of up to 8.19%, well above those of DSSC-based Pt CEs (7.87%). According to density functional theory (DFT) calculations, the outstanding electrocatalytic activity of Ni12P5/rGO as a CE in DSSCs was associated with the exceptional I3– adsorption capacity. These results prove that Ni12P5/rGO is a promising candidate to replace Pt as a CE in DSSCs.