Improving photo-stability and charge transport properties of Cu2O/CuO for photo-electrochemical water splitting using alternate layers of WO3 or CuWO4 produced by the same route

We report on remarkable stability improvement of Cu2O nanostructured thin films by deposition of a thin layer of WO3 or CuWO4 as an efficient photocathode for photoelectrochemical (PEC) water splitting. The modification of Cu2O thin films by WO3 or CuWO4 has been carried out by the same synthesization process just with different annealing temperatures. It is shown that the Cu2O nanostructures can partly be converted to CuO during the annealing process. The amount of conversion of Cu2O to CuO depends on the annealing temperature and its duration. The best photocurrent densities of −1.9 and −2.8 mA/cm2 have been obtained from the Cu2O/CuO/WO3 and CuO/CuWO4 heterostructures, respectively, which are at least 3 and 4 times higher than that of the bare Cu2O (−0.6 mA/cm2). Also, the stability improvement results show that the remaining photocurrent after 40 min for the WO3 or CuWO4 modifications reach to about 40% and 61%, which in comparison to the bare Cu2O (10%) are 4 and 6 times better, respectively. By performing various characterizations, it is shown that the improved photoresponse of the modified heterostructures is originated from more absorption of the light and consequently more photocurrent generation in the modified samples in addition to the enhanced charge transfer at the interface of photocathode/electrolyte.