▎ 摘　　要

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 I-3(-) adsorption capacity. These results prove that Ni12P5/rGO is a promising candidate to replace Pt as a CE in DSSCs.