CVD-grown copper tungstate thin films for solar water splitting

Abstract

In this paper, a direct chemical vapor deposition (CVD) approach is applied for the first time to synthesize high quality copper oxide (CuO), copper tungstate (CuWO4) and tungsten oxide (WO3) on F:SnO2 (FTO) substrates for photocatalytic water splitting.

Comparative Study of Photocarrier Dynamics in CVD-deposited CuWO4, CuO, and WO3 Thin Films for Photoelectrocatalysis

“…In this study, the photocarrier dynamics and transport properties of CVD deposited CuWO 4 thin films were analyzed by means of time-resolved conductivity measurements and compared to the binary counterparts CuO and WO 3 . As such experiments need to be performed on samples deposited on non-conductive substrates our CVD approach [16] that resulted in high quality CuWO 4 photoabsorber films on F:SnO 2 (FTO) was adapted to the deposition on quartz substrates. The process parameters could be tuned to yield stoichiometric, Cu-rich or W-rich films and deposits ranging from cupric oxide (CuO) via copper tungstate (CuWO 4 ) to tungsten oxide (WO 3 ) by adjusting the copper to tungsten ratio Cu/W.…”

“…or on quartz substrates using a custom built, horizontal cold-wall, low pressure MOCVD reactor; for details see Ref. [16]. Rutherford backscattering spectrometry (RBS) was used as a standard measurement for the determination of the elemental concentrations of the heavy elements Cu and W and in order to estimate the film thickness using the bulk density of the respective oxide.…”

“…Using the SimNRA program the elemental concentrations were simulated combining values from RBS and NRA [17]. Further details and material characterization have been reported elsewhere [16]. Ultraviolet-visible (UV/vis) spectra were recorded with a Shimadzu UV-2600 spectrometer equipped with an integrating sphere IRS-2600.…”

“…Recently we reported on a direct chemical vapor deposition (CVD) approach [16] which allowed to deposit stoichiometric CuWO 4 films by controlled variation of the Cu/W ratio between CuO, and WO 3 . Variation of CVD process parameters enabled us to tune the stoichiometry to obtain stoichiometric, W-rich, and Curich deposits.…”

Recent progress of tungsten- and molybdenum-based semiconductor materials for solar-hydrogen production

“…Compared to WO 3 that is only stable in acidic solutions, CuWO 4 shows an excellent stability in aqueous solutions with a pH range of 7-9 [161][162][163]. However, the obtained PEC performances of the CuWO 4 photoanodes are still far from their theoretical values considering the bandgap of 2.3 eV, and the major limitation is attributed to the low charge carrier mobility (~ 0.006 cm 2 V −1 s −1 ) and short charge diffusion length (~ 30 nm) that cause poor charge separation in the bulk CuWO 4 [164,165]. In addition, the surface states also affect the PEC water oxidation performance of the CuWO 4 photoanodes [166,167].…”