Ce-doped bundled ultrafine diameter tungsten oxide nanowires with enhanced electrochromic performance

Abstract

Cerium (Ce)-doped tungsten oxide nanostructures were synthesised using a simple solvothermal method from cerium chloride salt (CeCl37H2O) and tungsten hexachloride (WCl6¬) precursors. As-prepared samples were thoroughly characterised using electron microscopies, x-ray diffraction (XRD), x-ray photoelectron spectroscope (XPS) and Raman. The electrochromic performance of different samples was evaluated using a custom-built UV-VIS spectrometer and electrochemistry technique. The results showed that the as-prepared samples underwent morphological evolutions with increasing the Ce/W molar ratios, from long, thin and bundled nanowires, through shorter and thicker nanowires to mixed nanowire bundles and nanoparticle agglomerates. From electrochemical testing, we found that the Ce-doped tungsten oxides exhibited higher optical contrasts of 44.3%, 49.7% and 39.4% for the 1:15, 1:10 and 1:5 Ce/W ratio respectively, compared with 37.4% of the pure W18O49 nanowires. The Ce/W = 1:15 samples presented an improved colouration efficiency of 62 cm2/C against 51 cm2/C of pure W18O49. This work demonstrated that the Ce-doped W18O49 nanowires are very promising candidate materials for the design and construction of electrochemical chromic devices with largely improved efficiency, contrast and stability. The results from this work suggested that smart electrochromic devices based on current Ce-doped WOx nan